Adding upstream version 1.2.2.upstream/1.2.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

22 files changed, 6918 insertions, 0 deletions

diff --git a/src/trace/CMakeLists.txt b/src/trace/CMakeLists.txt
new file mode 100644
index 0000000..45b3125
--- /dev/null
+++ b/src/trace/CMakeLists.txt
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+set(trace_SRC
+	filterset.cpp
+	imagemap.cpp
+	imagemap-gdk.cpp
+	quantize.cpp
+	siox.cpp
+	trace.cpp
+
+	potrace/inkscape-potrace.cpp
+	autotrace/inkscape-autotrace.cpp
+	depixelize/inkscape-depixelize.cpp
+
+	# -------
+	# Headers
+	filterset.h
+	imagemap-gdk.h
+	imagemap.h
+	pool.h
+	quantize.h
+	siox.h
+	trace.h
+
+	potrace/bitmap.h
+	potrace/inkscape-potrace.h
+	autotrace/inkscape-autotrace.h
+	depixelize/inkscape-depixelize.h
+)
+
+add_inkscape_source("${trace_SRC}")
+
diff --git a/src/trace/README b/src/trace/README
new file mode 100644
index 0000000..f436aa0
--- /dev/null
+++ b/src/trace/README
@@ -0,0 +1,18 @@
+
+This directory contains code for converting bitmap images to vector images.
+The subdirectories contain code for the three tracers used in Inkscape: potrace
+(external dependency), autotrace, and libdepixelize (currently in src/3rdparty).
+
+
+To do:
+
+* Think about conceptually changing how the tracing works: Ideally, it should
+  be three steps clearly separated:
+  1/ Preprocessing (color reduction, blurring, background removing, image
+    inversion...)
+  2/ Tracing the preprocessed image, using some tracing engine
+  3/ Post-processing (suppressing speckles, optimizing paths...)
+  
+  The main problem is that the tracing engine sometimes *also* does 1 and 3, so
+  there is some discussion to have whether this can be done.
+
diff --git a/src/trace/autotrace/inkscape-autotrace.cpp b/src/trace/autotrace/inkscape-autotrace.cpp
new file mode 100644
index 0000000..d147890
--- /dev/null
+++ b/src/trace/autotrace/inkscape-autotrace.cpp
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * This is the C++ glue between Inkscape and Autotrace
+ *//*
+ *
+ * Authors:
+ *   Marc Jeanmougin
+ *
+ * Copyright (C) 2018 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ */
+
+#include "inkscape-autotrace.h"
+
+extern "C" {
+#include "3rdparty/autotrace/autotrace.h"
+#include "3rdparty/autotrace/output.h"
+#include "3rdparty/autotrace/spline.h"
+}
+
+#include <glibmm/i18n.h>
+#include <gtkmm/main.h>
+#include <iomanip>
+
+#include "trace/filterset.h"
+#include "trace/imagemap-gdk.h"
+#include "trace/quantize.h"
+
+#include "desktop.h"
+#include "message-stack.h"
+#include <inkscape.h>
+
+#include "object/sp-path.h"
+
+#include <svg/path-string.h>
+
+using Glib::ustring;
+
+// static void updateGui()
+// {
+//     //## Allow the GUI to update
+//     Gtk::Main::iteration(false); // at least once, non-blocking
+//     while (Gtk::Main::events_pending())
+//         Gtk::Main::iteration();
+// }
+
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Autotrace {
+
+static guchar* to_3channels(GdkPixbuf* input) {
+    if (!input) {
+        return nullptr;
+    }
+    int imgsize = gdk_pixbuf_get_height(input) * gdk_pixbuf_get_width(input);
+    guchar *out = (guchar*)malloc(3 * imgsize);
+    if (!out) {
+        g_warning("Autotrace::to_3channels: can not allocate memory for %d pixel image.", imgsize);
+        return nullptr;
+    }
+    int x=0;
+    guchar* pix = gdk_pixbuf_get_pixels (input);
+    int rs = gdk_pixbuf_get_rowstride (input);
+    for(int row=0;row<gdk_pixbuf_get_height(input);row++) {
+        for (int col=0;col<gdk_pixbuf_get_width(input);col++) {
+            guchar alpha = *(pix + row * rs + col * 4 + 3);
+            guchar white = 255 - alpha;
+            for(int chan=0;chan<3;chan++) {
+                // guchar *pnew = (pix + row * rs + col * 3 + chan);
+                guchar *pold = (pix + row * rs + col * 4 + chan);
+                out[x++] = (guchar)(((int)(*pold) * (int)alpha / 256) + white);
+            }
+        }
+    }
+    return out;
+}
+
+
+/**
+ *
+ */
+AutotraceTracingEngine::AutotraceTracingEngine()
+    : keepGoing(1)
+    , traceType(TRACE_OUTLINE)
+    , invert(false)
+{
+    /* get default parameters */
+    opts = at_fitting_opts_new();
+    opts->background_color = at_color_new(255,255,255);
+    autotrace_init();
+}
+
+AutotraceTracingEngine::~AutotraceTracingEngine() { at_fitting_opts_free(opts); }
+
+
+
+// TODO
+Glib::RefPtr<Gdk::Pixbuf> AutotraceTracingEngine::preview(Glib::RefPtr<Gdk::Pixbuf> thePixbuf) { 
+    //auto x = thePixbuf.copy();
+    guchar *pb = to_3channels(thePixbuf->gobj());
+    if (!pb) {
+        return Glib::RefPtr<Gdk::Pixbuf>();
+    }
+    return Gdk::Pixbuf::create_from_data(pb, thePixbuf->get_colorspace(), false, 8, thePixbuf->get_width(),
+                                         thePixbuf->get_height(), (thePixbuf->get_width() * 3),
+                                         [](const guint8 *pb) { free(const_cast<guint8 *>(pb)); });
+}
+
+int test_cancel (void* keepGoing){return !(* ((int*)keepGoing));}
+
+/**
+ *  This is the working method of this interface, and all
+ *  implementing classes.  Take a GdkPixbuf, trace it, and
+ *  return the path data that is compatible with the d="" attribute
+ *  of an SVG <path> element.
+ */
+std::vector<TracingEngineResult> AutotraceTracingEngine::trace(Glib::RefPtr<Gdk::Pixbuf> pixbuf)
+{
+    GdkPixbuf *pb1 = pixbuf->gobj();
+    guchar *pb = to_3channels(pb1);
+    if (!pb) {
+        return std::vector<TracingEngineResult>();
+    }
+    
+    at_bitmap *bitmap =
+//        at_bitmap_new(gdk_pixbuf_get_width(pb), gdk_pixbuf_get_height(pb), gdk_pixbuf_get_n_channels(pb));
+//    bitmap->bitmap = gdk_pixbuf_get_pixels(pb);
+    at_bitmap_new(gdk_pixbuf_get_width(pb1), gdk_pixbuf_get_height(pb1), 3);
+    free(bitmap->bitmap); // should create at_bitmap with bitmap->bitmap = pb
+    bitmap->bitmap = pb;
+    
+    at_splines_type *splines = at_splines_new_full(bitmap, opts, NULL, NULL, NULL, NULL, test_cancel, &keepGoing);
+    // at_output_write_func wfunc = at_output_get_handler_by_suffix("svg");
+    // at_spline_writer *wfunc = at_output_get_handler_by_suffix("svg");
+
+
+    int height = splines->height;
+    // const at_splines_type spline = *splines;
+    at_spline_list_array_type spline = *splines;
+
+    unsigned this_list;
+    at_spline_list_type list;
+    at_color last_color = { 0, 0, 0 };
+
+    std::stringstream theStyle;
+    std::stringstream thePath;
+    char color[10];
+    int nNodes = 0;
+
+    std::vector<TracingEngineResult> res;
+
+    // at_splines_write(wfunc, stdout, "", NULL, splines, NULL, NULL);
+
+    for (this_list = 0; this_list < SPLINE_LIST_ARRAY_LENGTH(spline); this_list++) {
+        unsigned this_spline;
+        at_spline_type first;
+
+        list = SPLINE_LIST_ARRAY_ELT(spline, this_list);
+        first = SPLINE_LIST_ELT(list, 0);
+
+        if (this_list == 0 || !at_color_equal(&list.color, &last_color)) {
+            if (this_list > 0) {
+                if (!(spline.centerline || list.open)) {
+                    thePath << "z";
+                    nNodes++;
+                }
+                TracingEngineResult ter(theStyle.str(), thePath.str(), nNodes);
+                res.push_back(ter);
+                theStyle.clear();
+                thePath.clear();
+                nNodes = 0;
+            }
+            sprintf(color, "#%02x%02x%02x;", list.color.r, list.color.g, list.color.b);
+
+            theStyle << ((spline.centerline || list.open) ? "stroke:" : "fill:") << color
+                     << ((spline.centerline || list.open) ? "fill:" : "stroke:") << "none";
+        }
+        thePath << "M" << START_POINT(first).x << " " << height - START_POINT(first).y;
+        nNodes++;
+        for (this_spline = 0; this_spline < SPLINE_LIST_LENGTH(list); this_spline++) {
+            at_spline_type s = SPLINE_LIST_ELT(list, this_spline);
+
+            if (SPLINE_DEGREE(s) == AT_LINEARTYPE) {
+                thePath << "L" << END_POINT(s).x << " " << height - END_POINT(s).y;
+                nNodes++;
+            }
+            else {
+                thePath << "C" << CONTROL1(s).x << " " << height - CONTROL1(s).y << " " << CONTROL2(s).x << " "
+                        << height - CONTROL2(s).y << " " << END_POINT(s).x << " " << height - END_POINT(s).y;
+                nNodes++;
+            }
+            last_color = list.color;
+        }
+    }
+    if (!(spline.centerline || list.open))
+        thePath << "z";
+    nNodes++;
+    if (SPLINE_LIST_ARRAY_LENGTH(spline) > 0) {
+        TracingEngineResult ter(theStyle.str(), thePath.str(), nNodes);
+        res.push_back(ter);
+        theStyle.clear();
+        thePath.clear();
+        nNodes = 0;
+    }
+
+    return res;
+}
+
+
+/**
+ *  Abort the thread that is executing getPathDataFromPixbuf()
+ */
+void AutotraceTracingEngine::abort()
+{
+    // g_message("PotraceTracingEngine::abort()\n");
+    keepGoing = 0;
+}
+
+
+
+} // namespace Autotrace
+} // namespace Trace
+} // namespace Inkscape
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/autotrace/inkscape-autotrace.h b/src/trace/autotrace/inkscape-autotrace.h
new file mode 100644
index 0000000..f12eb35
--- /dev/null
+++ b/src/trace/autotrace/inkscape-autotrace.h
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * This is the C++ glue between Inkscape and Autotrace
+ *//*
+ *
+ * Authors:
+ *   Marc Jeanmougin
+ *
+ * Copyright (C) 2018 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ * Autotrace is available at http://github.com/autotrace/autotrace.
+ *
+ */
+
+#ifndef __INKSCAPE_AUTOTRACE_H__
+#define __INKSCAPE_AUTOTRACE_H__
+
+#include "3rdparty/autotrace/autotrace.h"
+#include <trace/trace.h>
+
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Autotrace {
+enum TraceType { TRACE_CENTERLINE, TRACE_OUTLINE };
+
+class AutotraceTracingEngine : public TracingEngine {
+
+  public:
+    /**
+     *
+     */
+    AutotraceTracingEngine();
+
+    /**
+     *
+     */
+    ~AutotraceTracingEngine() override;
+
+
+    /**
+     * Sets/gets parameters
+     */
+    // TODO
+
+    /**
+     *  This is the working method of this implementing class, and all
+     *  implementing classes.  Take a GdkPixbuf, trace it, and
+     *  return the path data that is compatible with the d="" attribute
+     *  of an SVG <path> element.
+     */
+    std::vector<TracingEngineResult> trace(Glib::RefPtr<Gdk::Pixbuf> pixbuf) override;
+
+    /**
+     *  Abort the thread that is executing getPathDataFromPixbuf()
+     */
+    void abort() override;
+
+    /**
+     *
+     */
+    Glib::RefPtr<Gdk::Pixbuf> preview(Glib::RefPtr<Gdk::Pixbuf> pixbuf);
+
+    /**
+     *
+     */
+    int keepGoing;
+
+  //private:
+    // autotrace_param_t *autotraceParams;
+    TraceType traceType;
+    at_fitting_opts_type *opts;
+
+    //## do I invert at the end?
+    bool invert;
+
+}; // class AutotraceTracingEngine
+
+
+
+} // namespace Autotrace
+} // namespace Trace
+} // namespace Inkscape
+
+
+#endif //__INKSCAPE_POTRACE_H__
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/depixelize/inkscape-depixelize.cpp b/src/trace/depixelize/inkscape-depixelize.cpp
new file mode 100644
index 0000000..a61ff8b
--- /dev/null
+++ b/src/trace/depixelize/inkscape-depixelize.cpp
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This is the C++ glue between Inkscape and Potrace
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ * Potrace, the wonderful tracer located at http://potrace.sourceforge.net,
+ * is provided by the generosity of Peter Selinger, to whom we are grateful.
+ *
+ */
+
+#include "inkscape-depixelize.h"
+
+#include <glibmm/i18n.h>
+#include <gtkmm/main.h>
+#include <gtkmm.h>
+#include <iomanip>
+
+#include "desktop.h"
+#include "message-stack.h"
+#include "helper/geom.h"
+#include "object/sp-path.h"
+
+#include "display/cairo-templates.h"
+
+#include <svg/path-string.h>
+#include <svg/svg.h>
+#include <svg/svg-color.h>
+#include "svg/css-ostringstream.h"
+
+using Glib::ustring;
+
+
+
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Depixelize {
+
+
+/**
+ *
+ */
+DepixelizeTracingEngine::DepixelizeTracingEngine()
+    : keepGoing(1)
+    , traceType(TRACE_VORONOI)
+{
+    params = new ::Tracer::Kopf2011::Options();
+}
+
+
+
+DepixelizeTracingEngine::DepixelizeTracingEngine(TraceType traceType, double curves, int islands, int sparsePixels,
+                                                 double sparseMultiplier, bool optimize)
+    : keepGoing(1)
+    , traceType(traceType)
+{
+    params = new ::Tracer::Kopf2011::Options();
+    params->curvesMultiplier = curves;
+    params->islandsWeight = islands;
+    params->sparsePixelsRadius = sparsePixels;
+    params->sparsePixelsMultiplier = sparseMultiplier;
+    params->optimize = optimize;
+    params->nthreads = Inkscape::Preferences::get()->getIntLimited("/options/threading/numthreads",
+#ifdef HAVE_OPENMP
+                                                                   omp_get_num_procs(),
+#else
+                                                                   1,
+#endif // HAVE_OPENMP
+                                                                   1, 256);
+}
+
+DepixelizeTracingEngine::~DepixelizeTracingEngine() { delete params; }
+
+std::vector<TracingEngineResult> DepixelizeTracingEngine::trace(Glib::RefPtr<Gdk::Pixbuf> pixbuf)
+{
+    std::vector<TracingEngineResult> res;
+
+    if (pixbuf->get_width() > 256 || pixbuf->get_height() > 256) {
+        char *msg = _("Image looks too big. Process may take a while and it is"
+                      " wise to save your document before continuing."
+                      "\n\nContinue the procedure (without saving)?");
+        Gtk::MessageDialog dialog(msg, false, Gtk::MESSAGE_WARNING, Gtk::BUTTONS_OK_CANCEL, true);
+
+        if (dialog.run() != Gtk::RESPONSE_OK) {
+            return res;
+        }
+    }
+
+    ::Tracer::Splines splines;
+
+    if (traceType == TRACE_VORONOI)
+        splines = ::Tracer::Kopf2011::to_voronoi(pixbuf, *params);
+    else
+        splines = ::Tracer::Kopf2011::to_splines(pixbuf, *params);
+
+    for (::Tracer::Splines::const_iterator it = splines.begin(), end = splines.end(); it != end; ++it) {
+                gchar b[64];
+                sp_svg_write_color(b, sizeof(b),
+                                   SP_RGBA32_U_COMPOSE(unsigned(it->rgba[0]),
+                                                       unsigned(it->rgba[1]),
+                                                       unsigned(it->rgba[2]),
+                                                       unsigned(it->rgba[3])));
+        Inkscape::CSSOStringStream osalpha;
+        osalpha << float(it->rgba[3]) / 255.;
+        gchar* style = g_strdup_printf("fill:%s;fill-opacity:%s;", b, osalpha.str().c_str());
+        printf("%s\n", style);
+        TracingEngineResult r(style, sp_svg_write_path(it->pathVector), count_pathvector_nodes(it->pathVector));
+        res.push_back(r);
+        g_free(style);
+    }
+    return res;
+}
+
+void DepixelizeTracingEngine::abort() { keepGoing = 0; }
+
+Glib::RefPtr<Gdk::Pixbuf> DepixelizeTracingEngine::preview(Glib::RefPtr<Gdk::Pixbuf> pixbuf) { return pixbuf; }
+
+
+} // namespace Depixelize
+} // namespace Trace
+} // namespace Inkscape
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/depixelize/inkscape-depixelize.h b/src/trace/depixelize/inkscape-depixelize.h
new file mode 100644
index 0000000..85f6509
--- /dev/null
+++ b/src/trace/depixelize/inkscape-depixelize.h
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This is the C++ glue between Inkscape and Potrace
+ *
+ * Copyright (C) 2019 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ * Potrace, the wonderful tracer located at http://potrace.sourceforge.net,
+ * is provided by the generosity of Peter Selinger, to whom we are grateful.
+ *
+ */
+
+#ifndef __INKSCAPE_DEPIXTRACE_H__
+#define __INKSCAPE_DEPIXTRACE_H__
+
+#include <trace/trace.h>
+#include "3rdparty/libdepixelize/kopftracer2011.h"
+
+struct GrayMap_def;
+typedef GrayMap_def GrayMap;
+
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Depixelize {
+
+enum TraceType
+    {
+    TRACE_VORONOI,
+    TRACE_BSPLINES
+    };
+
+
+class DepixelizeTracingEngine : public TracingEngine
+{
+
+    public:
+
+    /**
+     *
+     */
+    DepixelizeTracingEngine();
+    DepixelizeTracingEngine(TraceType traceType, double curves, int islands, int sparsePixels, double sparseMultiplier, bool optimize);
+
+    /**
+     *
+     */
+    ~DepixelizeTracingEngine() override;
+
+    /**
+     *  This is the working method of this implementing class, and all
+     *  implementing classes.  Take a GdkPixbuf, trace it, and
+     *  return the path data that is compatible with the d="" attribute
+     *  of an SVG <path> element.
+     */
+    std::vector<TracingEngineResult> trace(
+                        Glib::RefPtr<Gdk::Pixbuf> pixbuf) override;
+
+    /**
+     *  Abort the thread that is executing getPathDataFromPixbuf()
+     */
+    void abort() override;
+
+    /**
+     *
+     */
+    Glib::RefPtr<Gdk::Pixbuf> preview(Glib::RefPtr<Gdk::Pixbuf> pixbuf);
+
+    /**
+     *
+     */
+    int keepGoing;
+
+    ::Tracer::Kopf2011::Options *params;
+    TraceType traceType;
+
+};//class PotraceTracingEngine
+
+
+
+}  // namespace Depixelize
+}  // namespace Trace
+}  // namespace Inkscape
+
+
+#endif  //__INKSCAPE_TRACE_H__
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/filterset.cpp b/src/trace/filterset.cpp
new file mode 100644
index 0000000..331d4e3
--- /dev/null
+++ b/src/trace/filterset.cpp
@@ -0,0 +1,428 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Some filters for Potrace in Inkscape
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <cstdio>
+#include <cstdlib>
+
+#include "imagemap-gdk.h"
+#include "filterset.h"
+#include "quantize.h"
+
+/*#########################################################################
+### G A U S S I A N  (smoothing)
+#########################################################################*/
+
+/**
+ *
+ */
+static int gaussMatrix[] =
+{
+     2,  4,  5,  4, 2,
+     4,  9, 12,  9, 4,
+     5, 12, 15, 12, 5,
+     4,  9, 12,  9, 4,
+     2,  4,  5,  4, 2
+};
+
+
+/**
+ *
+ */
+GrayMap *grayMapGaussian(GrayMap *me)
+{
+    int width  = me->width;
+    int height = me->height;
+    int firstX = 2;
+    int lastX  = width-3;
+    int firstY = 2;
+    int lastY  = height-3;
+
+    GrayMap *newGm = GrayMapCreate(width, height);
+    if (!newGm)
+        return nullptr;
+
+    for (int y = 0 ; y<height ; y++)
+        {
+        for (int x = 0 ; x<width ; x++)
+            {
+	    /* image boundaries */
+            if (x<firstX || x>lastX || y<firstY || y>lastY)
+                {
+                newGm->setPixel(newGm, x, y, me->getPixel(me, x, y));
+                continue;
+                }
+
+            /* all other pixels */
+            int gaussIndex = 0;
+            unsigned long sum = 0;
+            for (int i= y-2 ; i<=y+2 ; i++)
+                {
+                for (int j= x-2; j<=x+2 ; j++)
+                    {
+                    int weight = gaussMatrix[gaussIndex++];
+                    sum += me->getPixel(me, j, i) * weight;
+		    }
+	        }
+            sum /= 159;
+	    newGm->setPixel(newGm, x, y, sum);
+	    }
+	}
+
+    return newGm;
+}
+
+
+
+
+
+/**
+ *
+ */
+RgbMap *rgbMapGaussian(RgbMap *me)
+{
+    int width  = me->width;
+    int height = me->height;
+    int firstX = 2;
+    int lastX  = width-3;
+    int firstY = 2;
+    int lastY  = height-3;
+
+    RgbMap *newGm = RgbMapCreate(width, height);
+    if (!newGm)
+        return nullptr;
+
+    for (int y = 0 ; y<height ; y++)
+        {
+        for (int x = 0 ; x<width ; x++)
+            {
+	    /* image boundaries */
+            if (x<firstX || x>lastX || y<firstY || y>lastY)
+                {
+                newGm->setPixelRGB(newGm, x, y, me->getPixel(me, x, y));
+                continue;
+                }
+
+            /* all other pixels */
+            int gaussIndex = 0;
+            int sumR       = 0;
+            int sumG       = 0;
+            int sumB       = 0;
+            for (int i= y-2 ; i<=y+2 ; i++)
+                {
+                for (int j= x-2; j<=x+2 ; j++)
+                    {
+                    int weight = gaussMatrix[gaussIndex++];
+                    RGB rgb = me->getPixel(me, j, i);
+                    sumR += weight * (int)rgb.r;
+                    sumG += weight * (int)rgb.g;
+                    sumB += weight * (int)rgb.b;
+		    }
+	        }
+            RGB rout;
+            rout.r = ( sumR / 159 ) & 0xff;
+            rout.g = ( sumG / 159 ) & 0xff;
+            rout.b = ( sumB / 159 ) & 0xff;
+	    newGm->setPixelRGB(newGm, x, y, rout);
+	    }
+	}
+
+    return newGm;
+
+}
+
+
+
+
+/*#########################################################################
+### C A N N Y    E D G E    D E T E C T I O N
+#########################################################################*/
+
+
+static int sobelX[] =
+{
+    -1,  0,  1 ,
+    -2,  0,  2 ,
+    -1,  0,  1 
+};
+
+static int sobelY[] =
+{
+     1,  2,  1 ,
+     0,  0,  0 ,
+    -1, -2, -1 
+};
+
+
+
+/**
+ * Perform Sobel convolution on a GrayMap
+ */
+static GrayMap *grayMapSobel(GrayMap *gm, 
+               double dLowThreshold, double dHighThreshold)
+{
+    int width  = gm->width;
+    int height = gm->height;
+    int firstX = 1;
+    int lastX  = width-2;
+    int firstY = 1;
+    int lastY  = height-2;
+
+    GrayMap *newGm = GrayMapCreate(width, height);
+    if (!newGm)
+        return nullptr;
+
+    for (int y = 0 ; y<height ; y++)
+        {
+        for (int x = 0 ; x<width ; x++)
+            {
+            unsigned long sum = 0;
+	    /* image boundaries */
+            if (x<firstX || x>lastX || y<firstY || y>lastY)
+                {
+                sum = 0;
+                }
+            else
+                {
+                /* ### SOBEL FILTERING #### */
+                long sumX = 0;
+                long sumY = 0;
+                int sobelIndex = 0;
+                for (int i= y-1 ; i<=y+1 ; i++)
+                    {
+                    for (int j= x-1; j<=x+1 ; j++)
+                        {
+                        sumX += gm->getPixel(gm, j, i) * 
+                             sobelX[sobelIndex++];
+		        }
+	            }
+
+                sobelIndex = 0;
+                for (int i= y-1 ; i<=y+1 ; i++)
+                    {
+                    for (int j= x-1; j<=x+1 ; j++)
+                        {
+                        sumY += gm->getPixel(gm, j, i) * 
+                             sobelY[sobelIndex++];
+		        }
+	            }
+                /*###  GET VALUE ### */
+                sum = abs(sumX) + abs(sumY);
+
+                if (sum > 765)
+                    sum = 765;
+
+#if 0
+                /*###  GET ORIENTATION (slow, pedantic way) ### */
+                double orient = 0.0;
+                if (sumX==0)
+                    {
+                    if (sumY==0)
+                        orient = 0.0;
+                    else if (sumY<0)
+                        {
+                        sumY = -sumY;
+                        orient = 90.0;
+                        }
+                    else
+                        orient = 90.0;
+                    }
+                else
+                    {
+                    orient = 57.295779515 * atan2( ((double)sumY),((double)sumX) );
+                    if (orient < 0.0)
+                        orient += 180.0;
+                    }
+
+                /*###  GET EDGE DIRECTION ### */
+                int edgeDirection = 0;
+                if (orient < 22.5)
+                    edgeDirection = 0;
+	        else if (orient < 67.5)
+                    edgeDirection = 45;
+	        else if (orient < 112.5)
+                    edgeDirection = 90;
+	        else if (orient < 157.5)
+                    edgeDirection = 135;
+#else
+                /*###  GET EDGE DIRECTION (fast way) ### */
+                int edgeDirection = 0; /*x,y=0*/
+                if (sumX==0)
+                    {
+                    if (sumY!=0)
+                        edgeDirection = 90;
+                    }
+                else
+                   {
+                   /*long slope = sumY*1024/sumX;*/
+                   long slope = (sumY << 10)/sumX;
+                   if (slope > 2472 || slope< -2472)  /*tan(67.5)*1024*/
+                       edgeDirection = 90;
+                   else if (slope > 414) /*tan(22.5)*1024*/
+                       edgeDirection = 45;
+                   else if (slope < -414) /*-tan(22.5)*1024*/
+                       edgeDirection = 135;
+                   }
+
+#endif
+                /* printf("%ld %ld %f %d\n", sumX, sumY, orient, edgeDirection); */
+
+                /*### Get two adjacent pixels in edge direction ### */
+                unsigned long leftPixel;
+                unsigned long rightPixel;
+                if (edgeDirection == 0)
+                    {
+                    leftPixel  = gm->getPixel(gm, x-1, y);
+                    rightPixel = gm->getPixel(gm, x+1, y);
+                    }
+                else if (edgeDirection == 45)
+                    {
+                    leftPixel  = gm->getPixel(gm, x-1, y+1);
+                    rightPixel = gm->getPixel(gm, x+1, y-1);
+                    }
+                else if (edgeDirection == 90)
+                    {
+                    leftPixel  = gm->getPixel(gm, x, y-1);
+                    rightPixel = gm->getPixel(gm, x, y+1);
+                    }
+                else /*135 */
+                    {
+                    leftPixel  = gm->getPixel(gm, x-1, y-1);
+                    rightPixel = gm->getPixel(gm, x+1, y+1);
+                    }
+
+                /*### Compare current value to adjacent pixels ### */
+                /*### if less that either, suppress it ### */
+                if (sum < leftPixel || sum < rightPixel)
+                    sum = 0;
+                else
+                    {
+                    unsigned long highThreshold = 
+                          (unsigned long)(dHighThreshold * 765.0);
+                    unsigned long lowThreshold = 
+                          (unsigned long)(dLowThreshold * 765.0);
+                    if (sum >= highThreshold)
+                        sum = 765; /* EDGE.  3*255 this needs to be settable */
+                    else if (sum < lowThreshold)
+                        sum = 0; /* NONEDGE */
+                    else
+                        {
+                        if ( gm->getPixel(gm, x-1, y-1)> highThreshold ||
+                             gm->getPixel(gm, x  , y-1)> highThreshold ||
+                             gm->getPixel(gm, x+1, y-1)> highThreshold ||
+                             gm->getPixel(gm, x-1, y  )> highThreshold ||
+                             gm->getPixel(gm, x+1, y  )> highThreshold ||
+                             gm->getPixel(gm, x-1, y+1)> highThreshold ||
+                             gm->getPixel(gm, x  , y+1)> highThreshold ||
+                             gm->getPixel(gm, x+1, y+1)> highThreshold)
+                            sum = 765; /* EDGE fix me too */
+                        else
+                            sum = 0; /* NONEDGE */
+                        }
+                    }
+
+
+                }/* else */
+            if (sum==0) /* invert light & dark */
+                sum = 765;
+            else
+                sum = 0;
+            newGm->setPixel(newGm, x, y, sum);
+	    }/* for (x) */
+	}/* for (y) */
+
+    return newGm;
+}
+
+
+
+
+
+/**
+ *
+ */
+GrayMap *
+grayMapCanny(GrayMap *gm, double lowThreshold, double highThreshold)
+{
+    if (!gm)
+        return nullptr;
+
+    GrayMap *cannyGm = grayMapSobel(gm, lowThreshold, highThreshold);
+    if (!cannyGm)
+        return nullptr;
+    /*cannyGm->writePPM(cannyGm, "canny.ppm");*/
+
+    return cannyGm;
+}
+
+
+
+/*#########################################################################
+### Q U A N T I Z A T I O N
+#########################################################################*/
+
+/**
+ *  Experimental.  Work on this later
+ */
+GrayMap *quantizeBand(RgbMap *rgbMap, int nrColors)
+{
+
+    RgbMap *gaussMap = rgbMapGaussian(rgbMap);
+    if (!gaussMap)
+        return nullptr;
+    //gaussMap->writePPM(gaussMap, "rgbgauss.ppm");
+
+    IndexedMap *qMap = rgbMapQuantize(gaussMap, nrColors);
+    gaussMap->destroy(gaussMap);
+    if (!qMap)
+        return nullptr;
+    //qMap->writePPM(qMap, "rgbquant.ppm");
+
+    GrayMap *gm = GrayMapCreate(rgbMap->width, rgbMap->height);
+    if (!gm)
+        return nullptr;
+
+    // RGB is quantized.  There should now be a small set of (R+G+B)
+    for (int y=0 ; y<qMap->height ; y++)
+        {
+        for (int x=0 ; x<qMap->width ; x++)
+            {
+            RGB rgb = qMap->getPixelValue(qMap, x, y);
+            int sum = rgb.r + rgb.g + rgb.b;
+            if (sum & 1)
+                sum = 765;
+            else
+                sum = 0;
+	    // printf("%d %d %d : %d\n", rgb.r, rgb.g, rgb.b, index);
+            gm->setPixel(gm, x, y, sum);
+            }
+        }
+
+    qMap->destroy(qMap);
+
+    return gm;
+}
+
+
+/*#########################################################################
+### E N D    O F    F I L E
+#########################################################################*/
+
+
+
+
+
+
+
+
+
+
diff --git a/src/trace/filterset.h b/src/trace/filterset.h
new file mode 100644
index 0000000..d8da650
--- /dev/null
+++ b/src/trace/filterset.h
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Some filters for Potrace in Inkscape
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef __FILTERSET_H__
+#define __FILTERSET_H__
+
+#include "imagemap.h"
+
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ *  Apply gaussian blur to an GrayMap
+ */
+GrayMap *grayMapGaussian(GrayMap *gmap);
+
+/**
+ *  Apply gaussian bluf to an RgbMap
+ */
+RgbMap *rgbMapGaussian(RgbMap *rgbmap);
+
+/**
+ *
+ */
+GrayMap *grayMapCanny(GrayMap *gmap,
+             double lowThreshold, double highThreshold);
+
+/**
+ *
+ */
+GrayMap *quantizeBand(RgbMap *rgbmap, int nrColors);
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* __FILTERSET_H__ */
+
+/*#########################################################################
+### E N D    O F    F I L E
+#########################################################################*/
diff --git a/src/trace/imagemap-gdk.cpp b/src/trace/imagemap-gdk.cpp
new file mode 100644
index 0000000..10fe27e
--- /dev/null
+++ b/src/trace/imagemap-gdk.cpp
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#include <cstdlib>
+
+#include "imagemap-gdk.h"
+
+
+/*#########################################################################
+## G R A Y M A P
+#########################################################################*/
+
+GrayMap *gdkPixbufToGrayMap(GdkPixbuf *buf)
+{
+    if (!buf)
+        return nullptr;
+
+    int width       = gdk_pixbuf_get_width(buf);
+    int height      = gdk_pixbuf_get_height(buf);
+    guchar *pixdata = gdk_pixbuf_get_pixels(buf);
+    int rowstride   = gdk_pixbuf_get_rowstride(buf);
+    int n_channels  = gdk_pixbuf_get_n_channels(buf);
+
+    GrayMap *grayMap = GrayMapCreate(width, height);
+    if (!grayMap)
+        return nullptr;
+
+    //### Fill in the odd cells with RGB values
+    int x,y;
+    int row  = 0;
+    for (y=0 ; y<height ; y++)
+        {
+        guchar *p = pixdata + row;
+        for (x=0 ; x<width ; x++)
+            {
+            int alpha = (int)p[3];
+            int white = 3 * (255-alpha);
+            unsigned long sample = (int)p[0] + (int)p[1] +(int)p[2];
+            unsigned long bright = sample * alpha / 256 + white;
+            grayMap->setPixel(grayMap, x, y, bright);
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+
+    return grayMap;
+}
+
+GdkPixbuf *grayMapToGdkPixbuf(GrayMap *grayMap)
+{
+    if (!grayMap)
+        return nullptr;
+
+    guchar *pixdata = (guchar *)
+          malloc(sizeof(guchar) * grayMap->width * grayMap->height * 3);
+    if (!pixdata)
+        {
+        g_warning("grayMapToGdkPixbuf: can not allocate memory for conversion.");
+        return nullptr;
+        }
+
+    int n_channels = 3;
+    int rowstride  = grayMap->width * 3;
+
+    GdkPixbuf *buf = gdk_pixbuf_new_from_data(pixdata, GDK_COLORSPACE_RGB,
+                        0, 8, grayMap->width, grayMap->height,
+                        rowstride, (GdkPixbufDestroyNotify)g_free, nullptr);
+
+    //### Fill in the odd cells with RGB values
+    int x,y;
+    int row  = 0;
+    for (y=0 ; y<grayMap->height ; y++)
+        {
+        guchar *p = pixdata + row;
+        for (x=0 ; x<grayMap->width ; x++)
+            {
+            unsigned long pix = grayMap->getPixel(grayMap, x, y) / 3;
+            p[0] = p[1] = p[2] = (guchar)(pix & 0xff);
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+
+    return buf;
+}
+
+
+/*#########################################################################
+## R G B   M A P
+#########################################################################*/
+
+RgbMap *gdkPixbufToRgbMap(GdkPixbuf *buf)
+{
+    if (!buf)
+        return nullptr;
+
+    int width       = gdk_pixbuf_get_width(buf);
+    int height      = gdk_pixbuf_get_height(buf);
+    guchar *pixdata = gdk_pixbuf_get_pixels(buf);
+    int rowstride   = gdk_pixbuf_get_rowstride(buf);
+    int n_channels  = gdk_pixbuf_get_n_channels(buf);
+
+    RgbMap *rgbMap = RgbMapCreate(width, height);
+    if (!rgbMap)
+        return nullptr;
+
+    //### Fill in the cells with RGB values
+    int x,y;
+    int row  = 0;
+    for (y=0 ; y<height ; y++)
+        {
+        guchar *p = pixdata + row;
+        for (x=0 ; x<width ; x++)
+            {
+            int alpha = (int)p[3];
+            int white = 255 - alpha;
+            int r     = (int)p[0];  r = r * alpha / 256 + white;
+            int g     = (int)p[1];  g = g * alpha / 256 + white;
+            int b     = (int)p[2];  b = b * alpha / 256 + white;
+
+            rgbMap->setPixel(rgbMap, x, y, r, g, b);
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+
+    return rgbMap;
+}
+
+
+
+/*#########################################################################
+## I N D E X E D   M A P
+#########################################################################*/
+
+
+GdkPixbuf *indexedMapToGdkPixbuf(IndexedMap *iMap)
+{
+    if (!iMap)
+        return nullptr;
+
+    guchar *pixdata = (guchar *)
+          malloc(sizeof(guchar) * iMap->width * iMap->height * 3);
+    if (!pixdata)
+        {
+        g_warning("indexedMapToGdkPixbuf: can not allocate memory for conversion.");
+        return nullptr;
+        }
+
+    int n_channels = 3;
+    int rowstride  = iMap->width * 3;
+
+    GdkPixbuf *buf = gdk_pixbuf_new_from_data(pixdata, GDK_COLORSPACE_RGB,
+                        0, 8, iMap->width, iMap->height,
+                        rowstride, (GdkPixbufDestroyNotify)g_free, nullptr);
+
+    //### Fill in the cells with RGB values
+    int x,y;
+    int row  = 0;
+    for (y=0 ; y<iMap->height ; y++)
+        {
+        guchar *p = pixdata + row;
+        for (x=0 ; x<iMap->width ; x++)
+            {
+            RGB rgb = iMap->getPixelValue(iMap, x, y);
+            p[0] = rgb.r & 0xff;
+            p[1] = rgb.g & 0xff;
+            p[2] = rgb.b & 0xff;
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+
+    return buf;
+}
+
+/*#########################################################################
+## E N D    O F    F I L E
+#########################################################################*/
diff --git a/src/trace/imagemap-gdk.h b/src/trace/imagemap-gdk.h
new file mode 100644
index 0000000..a96395b
--- /dev/null
+++ b/src/trace/imagemap-gdk.h
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2013 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#ifndef __GRAYMAP_GDK_H__
+#define __GRAYMAP_GDK_H__
+
+#ifndef TRUE
+#define TRUE  1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+#include "imagemap.h"
+
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+/*#########################################################################
+### I M A G E    M A P --- GDK
+#########################################################################*/
+
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+GrayMap *gdkPixbufToGrayMap(GdkPixbuf *buf);
+GdkPixbuf *grayMapToGdkPixbuf(GrayMap *grayMap);
+RgbMap *gdkPixbufToRgbMap(GdkPixbuf *buf);
+GdkPixbuf *indexedMapToGdkPixbuf(IndexedMap *iMap);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* __GRAYMAP_GDK_H__ */
+
+/*#########################################################################
+### E N D    O F    F I L E
+#########################################################################*/
diff --git a/src/trace/imagemap.cpp b/src/trace/imagemap.cpp
new file mode 100644
index 0000000..ff54b7e
--- /dev/null
+++ b/src/trace/imagemap.cpp
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#include <cstdlib>
+
+#include "imagemap.h"
+
+#include "io/sys.h"
+
+/*#########################################################################
+### G R A Y   M A P
+#########################################################################*/
+
+
+static void gSetPixel(GrayMap *me, int x, int y, unsigned long val)
+{
+    if (val>765)
+        val = 765;
+    unsigned long *pix = me->rows[y] + x;
+    *pix = val;
+}
+
+static unsigned long gGetPixel(GrayMap *me, int x, int y)
+{
+    unsigned long *pix = me->rows[y] + x;
+    return *pix;
+}
+
+
+static int gWritePPM(GrayMap *me, char *fileName)
+{
+    if (!fileName)
+        return FALSE;
+
+    FILE *f = fopen(fileName, "wb");
+    if (!f)
+        return FALSE;
+
+    fprintf(f, "P6 %d %d 255\n", me->width, me->height);
+
+    for (int y=0 ; y<me->height; y++)
+        {
+        for (int x=0 ; x<me->width ; x++)
+            {
+            unsigned long pix  = me->getPixel(me, x, y) / 3;
+            unsigned char pixb = (unsigned char) (pix & 0xff);
+            fputc(pixb, f);
+            fputc(pixb, f);
+            fputc(pixb, f);
+            }
+        }
+    fclose(f);
+    return TRUE;
+}
+
+
+static void gDestroy(GrayMap *me)
+{
+    if (me->pixels)
+        free(me->pixels);
+    if (me->rows)
+        free(me->rows);
+    free(me);
+}
+
+GrayMap *GrayMapCreate(int width, int height)
+{
+
+    GrayMap *me = (GrayMap *)malloc(sizeof(GrayMap));
+    if (!me)
+        return nullptr;
+
+    /** methods **/
+    me->setPixel    = gSetPixel;
+    me->getPixel    = gGetPixel;
+    me->writePPM    = gWritePPM;
+    me->destroy     = gDestroy;
+
+    /** fields **/
+    me->width  = width;
+    me->height = height;
+    me->pixels = (unsigned long *)
+              malloc(sizeof(unsigned long) * width * height);
+    if (!me->pixels)
+        {
+        g_warning("GrayMapCreate: can not allocate memory for %d x %d image.", width, height);
+        free(me);
+        return nullptr;
+        }
+    me->rows = (unsigned long **)
+              malloc(sizeof(unsigned long *) *  height);
+    if (!me->rows)
+        {
+        g_warning("GrayMapCreate: can not allocate memory for index of %d x %d image.", width, height);
+        free(me->pixels);
+        free(me);
+        return nullptr;
+        }
+
+    unsigned long *row = me->pixels;
+    for (int i=0 ; i<height ; i++)
+        {
+        me->rows[i] = row;
+        row += width;
+        }
+
+    return me;
+}
+
+
+
+/*#########################################################################
+### R G B      M A P
+#########################################################################*/
+
+
+
+static void rSetPixel(RgbMap *me, int x, int y, int r, int g, int b)
+{
+    RGB *pix = me->rows[y] + x;
+    pix->r = r;
+    pix->g = g;
+    pix->b = b;
+}
+
+static void rSetPixelRGB(RgbMap *me, int x, int y, RGB rgb)
+{
+    RGB *pix = me->rows[y] + x;
+    *pix = rgb;
+}
+
+static RGB rGetPixel(RgbMap *me, int x, int y)
+{
+    RGB *pix = me->rows[y] + x;
+    return *pix;
+}
+
+
+
+static int rWritePPM(RgbMap *me, char *fileName)
+{
+    if (!fileName)
+        return FALSE;
+
+    FILE *f = fopen(fileName, "wb");
+    if (!f)
+        return FALSE;
+
+    fprintf(f, "P6 %d %d 255\n", me->width, me->height);
+
+    for (int y=0 ; y<me->height; y++)
+        {
+        for (int x=0 ; x<me->width ; x++)
+            {
+            RGB rgb = me->getPixel(me, x, y);
+            fputc(rgb.r, f);
+            fputc(rgb.g, f);
+            fputc(rgb.b, f);
+            }
+        }
+    fclose(f);
+    return TRUE;
+}
+
+
+static void rDestroy(RgbMap *me)
+{
+    if (me->pixels){
+        free(me->pixels);
+    }
+    if (me->rows){
+        free(me->rows);
+    }
+    free(me);
+}
+
+
+
+RgbMap *RgbMapCreate(int width, int height)
+{
+
+    RgbMap *me = (RgbMap *)malloc(sizeof(RgbMap));
+    if (!me){
+        return nullptr;
+    }
+    
+    /** methods **/
+    me->setPixel    = rSetPixel;
+    me->setPixelRGB = rSetPixelRGB;
+    me->getPixel    = rGetPixel;
+    me->writePPM    = rWritePPM;
+    me->destroy     = rDestroy;
+
+
+    /** fields **/
+    me->width  = width;
+    me->height = height;
+    me->pixels = (RGB *) malloc(sizeof(RGB) * width * height);
+    if (!me->pixels){
+        g_warning("RgbMapCreate: can not allocate memory for %d x %d image.", width, height);
+        free(me);
+        return nullptr;
+    }
+    me->rows = (RGB **) malloc(sizeof(RGB *) * height);
+    if (!me->rows){
+        g_warning("RgbMapCreate: can not allocate memory for index of %d x %d image.", width, height);
+        free(me->pixels); //allocated as me->pixels is not NULL here: see previous check
+        free(me);
+        return nullptr;
+    }
+
+    RGB *row = me->pixels;
+    for (int i=0 ; i<height ; i++){
+        me->rows[i] = row;
+        row += width;
+    }
+
+    return me;
+}
+
+
+
+
+/*#########################################################################
+### I N D E X E D      M A P
+#########################################################################*/
+
+
+
+static void iSetPixel(IndexedMap *me, int x, int y, unsigned int index)
+{
+    unsigned int *pix = me->rows[y] + x;
+    *pix = index;
+}
+
+
+static unsigned int iGetPixel(IndexedMap *me, int x, int y)
+{
+    unsigned int *pix = me->rows[y] + x;
+    return *pix;
+}
+
+static RGB iGetPixelValue(IndexedMap *me, int x, int y)
+{
+    unsigned int *pix = me->rows[y] + x;
+    RGB rgb = me->clut[((*pix)&0xff)];
+    return rgb;
+}
+
+
+
+static int iWritePPM(IndexedMap *me, char *fileName)
+{
+    if (!fileName)
+        return FALSE;
+
+    FILE *f = fopen(fileName, "wb");
+    if (!f)
+        return FALSE;
+
+    fprintf(f, "P6 %d %d 255\n", me->width, me->height);
+
+    for (int y=0 ; y<me->height; y++)
+        {
+        for (int x=0 ; x<me->width ; x++)
+            {
+            RGB rgb = me->getPixelValue(me, x, y);
+            fputc(rgb.r, f);
+            fputc(rgb.g, f);
+            fputc(rgb.b, f);
+            }
+        }
+    fclose(f);
+    return TRUE;
+}
+
+
+static void iDestroy(IndexedMap *me)
+{
+    if (me->pixels){
+        free(me->pixels);
+    }
+    if (me->rows){
+        free(me->rows);
+    }
+    free(me);
+}
+
+
+
+IndexedMap *IndexedMapCreate(int width, int height)
+{
+
+    IndexedMap *me = (IndexedMap *)malloc(sizeof(IndexedMap));
+    if (!me)
+        return nullptr;
+
+    /** methods **/
+    me->setPixel      = iSetPixel;
+    me->getPixel      = iGetPixel;
+    me->getPixelValue = iGetPixelValue;
+    me->writePPM      = iWritePPM;
+    me->destroy       = iDestroy;
+
+
+    /** fields **/
+    me->width  = width;
+    me->height = height;
+    me->pixels = (unsigned int *) malloc(sizeof(unsigned int) * width * height);
+    if (!me->pixels){
+        g_warning("IndexedMapCreate: can not allocate memory for %d x %d image.", width, height);
+        free(me);
+        return nullptr;
+    }
+    me->rows = (unsigned int **) malloc(sizeof(unsigned int *) * height);
+    if (!me->rows){
+        g_warning("IndexedMapCreate: can not allocate memory for index of %d x %d image.", width, height);
+        free(me->pixels); //allocated as me->pixels is not NULL here: see previous check
+        free(me);
+        return nullptr;
+    }
+
+    unsigned int *row = me->pixels;
+    for (int i=0 ; i<height ; i++){
+        me->rows[i] = row;
+        row += width;
+    }
+
+    me->nrColors = 0;
+
+    RGB rgb;
+    rgb.r = rgb.g = rgb.b = 0;
+    for (auto & i : me->clut){
+        i = rgb;
+    }
+
+    return me;
+}
+
+
+
+
+
+
+/*#########################################################################
+### E N D    O F    F I L E
+#########################################################################*/
diff --git a/src/trace/imagemap.h b/src/trace/imagemap.h
new file mode 100644
index 0000000..4a938da
--- /dev/null
+++ b/src/trace/imagemap.h
@@ -0,0 +1,302 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#ifndef __IMAGEMAP_H__
+#define __IMAGEMAP_H__
+
+#ifndef TRUE
+#define TRUE  1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+
+/*#########################################################################
+### G R A Y M A P
+#########################################################################*/
+
+
+typedef struct GrayMap_def GrayMap;
+
+#define GRAYMAP_BLACK 0
+#define GRAYMAP_WHITE 765
+
+/**
+ *
+ */
+struct GrayMap_def
+{
+
+    /*#################
+    ### METHODS
+    #################*/
+
+    /**
+     *
+     */
+    void (*setPixel)(GrayMap *me, int x, int y, unsigned long val);
+
+    /**
+     *
+     */
+    unsigned long (*getPixel)(GrayMap *me, int x, int y);
+
+    /**
+     *
+     */
+    int (*writePPM)(GrayMap *me, char *fileName);
+
+
+
+    /**
+     *
+     */
+    void (*destroy)(GrayMap *me);
+
+
+
+    /*#################
+    ### FIELDS
+    #################*/
+
+    /**
+     *
+     */
+    int width;
+
+    /**
+     *
+     */
+    int height;
+
+    /**
+     *  The pixel array
+     */
+    unsigned long *pixels;
+
+    /**
+     *  Pointer to the beginning of each row
+     */
+    unsigned long **rows;
+
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+GrayMap *GrayMapCreate(int width, int height);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+
+/*#########################################################################
+### R G B   M A P
+#########################################################################*/
+
+struct RGB
+{
+    unsigned char r;
+    unsigned char g;
+    unsigned char b;
+};
+
+
+
+typedef struct RgbMap_def RgbMap;
+
+/**
+ *
+ */
+struct RgbMap_def
+{
+
+    /*#################
+    ### METHODS
+    #################*/
+
+    /**
+     *
+     */
+    void (*setPixel)(RgbMap *me, int x, int y, int r, int g, int b);
+
+
+    /**
+     *
+     */
+    void (*setPixelRGB)(RgbMap *me, int x, int y, RGB rgb);
+
+    /**
+     *
+     */
+    RGB (*getPixel)(RgbMap *me, int x, int y);
+
+    /**
+     *
+     */
+    int (*writePPM)(RgbMap *me, char *fileName);
+
+
+
+    /**
+     *
+     */
+    void (*destroy)(RgbMap *me);
+
+
+
+    /*#################
+    ### FIELDS
+    #################*/
+
+    /**
+     *
+     */
+    int width;
+
+    /**
+     *
+     */
+    int height;
+
+    /**
+     * The allocated array of pixels
+     */
+    RGB *pixels;
+
+    /**
+     * Pointers to the beginning of each row of pixels
+     */
+    RGB **rows;
+
+};
+
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+RgbMap *RgbMapCreate(int width, int height);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+
+
+/*#########################################################################
+### I N D E X E D     M A P
+#########################################################################*/
+
+
+typedef struct IndexedMap_def IndexedMap;
+
+/**
+ *
+ */
+struct IndexedMap_def
+{
+
+    /*#################
+    ### METHODS
+    #################*/
+
+    /**
+     *
+     */
+    void (*setPixel)(IndexedMap *me, int x, int y, unsigned int index);
+
+
+    /**
+     *
+     */
+    unsigned int (*getPixel)(IndexedMap *me, int x, int y);
+
+    /**
+     *
+     */
+    RGB (*getPixelValue)(IndexedMap *me, int x, int y);
+
+    /**
+     *
+     */
+    int (*writePPM)(IndexedMap *me, char *fileName);
+
+
+
+    /**
+     *
+     */
+    void (*destroy)(IndexedMap *me);
+
+
+
+    /*#################
+    ### FIELDS
+    #################*/
+
+    /**
+     *
+     */
+    int width;
+
+    /**
+     *
+     */
+    int height;
+
+    /**
+     * The allocated array of pixels
+     */
+    unsigned int *pixels;
+
+    /**
+     * Pointers to the beginning of each row of pixels
+     */
+    unsigned int **rows;
+
+    /**
+     *
+     */
+    int nrColors;
+
+    /**
+     * Color look up table
+     */
+    RGB clut[256];
+
+};
+
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+IndexedMap *IndexedMapCreate(int width, int height);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+
+
+#endif /* __IMAGEMAP_H__ */
+
+/*#########################################################################
+### E N D    O F    F I L E
+#########################################################################*/
diff --git a/src/trace/pool.h b/src/trace/pool.h
new file mode 100644
index 0000000..4c088b8
--- /dev/null
+++ b/src/trace/pool.h
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Pool memory allocation
+ *
+ * Authors:
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+// not thread safe (a pool cannot be shared by threads safely)
+
+/*
+-- principle:
+
+ - user operations on a pool of objects of type T are:
+   - T *draw() : obtain a unused slot to store an object T
+   - void drop(T *) : release a slot
+
+-- implementation:
+
+ - a pool for objects T is:
+
+   * blocks[64] : an array of allocated blocks of memory:
+     |---0--> block with capacity 64
+     |---1--> block with capacity 64
+     |---2--> block with capacity 128
+     |---3--> block with capacity 128
+     |---4--> block with capacity 256
+     |---5--> block with capacity 256
+     |---6--> block with capacity 512
+     |---7--> not yet allocated
+     :
+     |---k--> not yet allocated (future capacity ~ 2^(6+k/2))
+     :
+     '--63--> not yet allocated
+   * cblock : the index of the next unallocated block (here 7).
+   * next : a pointer to an unused slot inside an allocated bloc
+
+ - the first bytes of an unallocated slot inside a bloc are used to store a
+   pointer to some other unallocated slot. (this way, we keep a list of all
+   unused slots starting at <next>)
+
+ - insertions and deletions in this list are done at the root <next>.
+   if <next> points to NULL (no slots are available) when a draw()
+   operation is performed a new block is allocated, and the unused slots
+   list is filled with the allocated slots.
+
+ - memory is freed only at pool's deletion.
+
+*/
+
+#include <cstdlib>
+
+template <typename T>
+class pool {
+
+ public:
+
+  pool()
+  {
+      cblock = 0;
+      size = sizeof(T) > sizeof(void *) ? sizeof(T) : sizeof(void *);
+      next = nullptr;
+      for (auto & k : block) {
+          k = nullptr;
+      }
+  }
+
+  ~pool()
+  {
+      for (int k = 0; k < cblock; k++) {
+        free(block[k]);
+      }
+  }
+
+  T *draw()
+  {
+    if (!next) addblock();
+    void *p = next;
+    next = *(void **)p;
+    return (T *) p;
+  }
+
+  void drop(T *p)
+  {
+    *(void **)p = next;
+    next = (void *) p;
+  }
+
+ private:
+
+  int size;
+  int cblock;
+  void *block[64]; //enough to store unlimited number of objects, if 64 is changed: see constructor too
+  void *next;
+
+  void addblock()
+    {
+      int i = cblock++;
+      int blocksize = 1 << (6 + (i/2));
+      //printf("pool allocating block: %d (size:%d)...", i, blocksize);//debug
+      block[i] = (void *)malloc(blocksize * size);
+      if (!block[i]) throw std::bad_alloc();
+      char *p = (char *)block[i];
+      for (int k = 0; k < blocksize - 1; k++)
+	{
+	  *(void**)p = (void *)(p + size);
+	  p += size;
+	}
+      *(void **)p = next;
+      next = block[i];
+      //printf("done\n");//debug
+    }
+
+};
+
diff --git a/src/trace/potrace/bitmap.h b/src/trace/potrace/bitmap.h
new file mode 100644
index 0000000..2fb07e8
--- /dev/null
+++ b/src/trace/potrace/bitmap.h
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * inline macros for accessing bitmaps
+ */
+/* Copyright (C) 2001-2015 Peter Selinger.
+   This file is part of Potrace. It is free software and it is covered
+   by the GNU General Public License. See the file COPYING for details. */
+
+#ifndef BITMAP_H
+#define BITMAP_H
+
+#include <cstring>
+#include <cstdlib>
+#include <cerrno>
+#include <cstddef>
+
+/* The bitmap type is defined in potracelib.h */
+#include "potracelib.h"
+
+/* The present file defines some convenient macros and static inline
+   functions for accessing bitmaps. Since they only produce inline
+   code, they can be conveniently shared by the library and frontends,
+   if desired */
+
+/* ---------------------------------------------------------------------- */
+/* some measurements */
+
+#define BM_WORDSIZE ((int)sizeof(potrace_word))
+#define BM_WORDBITS (8*BM_WORDSIZE)
+#define BM_HIBIT (((potrace_word)1)<<(BM_WORDBITS-1))
+#define BM_ALLBITS (~(potrace_word)0)
+
+/* macros for accessing pixel at index (x,y). U* macros omit the
+   bounds check. */
+
+#define bm_scanline(bm, y) ((bm)->map + (ptrdiff_t)(y)*(ptrdiff_t)(bm)->dy)
+#define bm_index(bm, x, y) (&bm_scanline(bm, y)[(x)/BM_WORDBITS])
+#define bm_mask(x) (BM_HIBIT >> ((x) & (BM_WORDBITS-1)))
+#define bm_range(x, a) ((int)(x) >= 0 && (int)(x) < (a))
+#define bm_safe(bm, x, y) (bm_range(x, (bm)->w) && bm_range(y, (bm)->h))
+#define BM_UGET(bm, x, y) ((*bm_index(bm, x, y) & bm_mask(x)) != 0)
+#define BM_USET(bm, x, y) (*bm_index(bm, x, y) |= bm_mask(x))
+#define BM_UCLR(bm, x, y) (*bm_index(bm, x, y) &= ~bm_mask(x))
+#define BM_UINV(bm, x, y) (*bm_index(bm, x, y) ^= bm_mask(x))
+#define BM_UPUT(bm, x, y, b) ((b) ? BM_USET(bm, x, y) : BM_UCLR(bm, x, y))
+#define BM_GET(bm, x, y) (bm_safe(bm, x, y) ? BM_UGET(bm, x, y) : 0)
+#define BM_SET(bm, x, y) (bm_safe(bm, x, y) ? BM_USET(bm, x, y) : 0)
+#define BM_CLR(bm, x, y) (bm_safe(bm, x, y) ? BM_UCLR(bm, x, y) : 0)
+#define BM_INV(bm, x, y) (bm_safe(bm, x, y) ? BM_UINV(bm, x, y) : 0)
+#define BM_PUT(bm, x, y, b) (bm_safe(bm, x, y) ? BM_UPUT(bm, x, y, b) : 0)
+
+/* free the given bitmap. Leaves errno untouched. */
+static inline void bm_free(potrace_bitmap_t *bm) {
+  if (bm) {
+    free(bm->map);
+  }
+  free(bm);
+}
+
+/* return new un-initialized bitmap. NULL with errno on error.
+   Assumes w, h >= 0. */
+static inline potrace_bitmap_t *bm_new(int w, int h) {
+  potrace_bitmap_t *bm;
+  int dy = w == 0 ? 0 : (w - 1) / BM_WORDBITS + 1;
+  ptrdiff_t size = (ptrdiff_t)dy * (ptrdiff_t)h * (ptrdiff_t)BM_WORDSIZE;
+
+  /* check for overflow error */
+  if (size < 0 || (h != 0 && dy != 0 && size / h / dy != BM_WORDSIZE)) {
+    errno = ENOMEM;
+    return nullptr;
+  }
+
+  bm = (potrace_bitmap_t *) malloc(sizeof(potrace_bitmap_t));
+  if (!bm) {
+    return nullptr;
+  }
+  bm->w = w;
+  bm->h = h;
+  bm->dy = dy;
+  bm->map = (potrace_word *) malloc(size);
+  if (!bm->map) {
+    g_warning("bm_new: can not allocate memory for bitmap (%td).", size);
+    free(bm);
+    return nullptr;
+  }
+  return bm;
+}
+
+/* clear the given bitmap. Set all bits to c. */
+static inline void bm_clear(potrace_bitmap_t *bm, int c) {
+  /* Note: if the bitmap was created with bm_new, then it is
+     guaranteed that size will fit into the ptrdiff_t type. */
+  ptrdiff_t size = (ptrdiff_t)bm->dy * (ptrdiff_t)bm->h * (ptrdiff_t)BM_WORDSIZE;
+  memset(bm->map, c ? -1 : 0, size);
+}
+
+/* duplicate the given bitmap. Return NULL on error with errno set. */
+static inline potrace_bitmap_t *bm_dup(const potrace_bitmap_t *bm) {
+  potrace_bitmap_t *bm1 = bm_new(bm->w, bm->h);
+  ptrdiff_t size = (ptrdiff_t)bm->dy * (ptrdiff_t)bm->h * (ptrdiff_t)BM_WORDSIZE;
+  if (!bm1) {
+    return nullptr;
+  }
+  memcpy(bm1->map, bm->map, size);
+  return bm1;
+}
+
+/* invert the given bitmap. */
+static inline void bm_invert(potrace_bitmap_t *bm) {
+  ptrdiff_t i;
+  ptrdiff_t size = (ptrdiff_t)bm->dy * (ptrdiff_t)bm->h;
+
+  for (i = 0; i < size; i++) {
+    bm->map[i] ^= BM_ALLBITS;
+  }
+}
+
+#endif /* BITMAP_H */
diff --git a/src/trace/potrace/inkscape-potrace.cpp b/src/trace/potrace/inkscape-potrace.cpp
new file mode 100644
index 0000000..d6e9b8f
--- /dev/null
+++ b/src/trace/potrace/inkscape-potrace.cpp
@@ -0,0 +1,679 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This is the C++ glue between Inkscape and Potrace
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ * Potrace, the wonderful tracer located at http://potrace.sourceforge.net,
+ * is provided by the generosity of Peter Selinger, to whom we are grateful.
+ *
+ */
+
+#include "inkscape-potrace.h"
+
+#include <glibmm/i18n.h>
+#include <gtkmm/main.h>
+#include <iomanip>
+
+#include "trace/filterset.h"
+#include "trace/quantize.h"
+#include "trace/imagemap-gdk.h"
+
+#include <inkscape.h>
+#include "desktop.h"
+#include "message-stack.h"
+
+#include "object/sp-path.h"
+
+#include <svg/path-string.h>
+#include "bitmap.h"
+
+using Glib::ustring;
+
+static void updateGui()
+{
+   //## Allow the GUI to update
+   Gtk::Main::iteration(false); //at least once, non-blocking
+   while( Gtk::Main::events_pending() )
+       Gtk::Main::iteration();
+
+}
+
+
+static void potraceStatusCallback(double /*progress*/, void *userData) /* callback fn */
+{
+    updateGui();
+
+    if (!userData)
+        return;
+
+    //g_message("progress: %f\n", progress);
+
+    //Inkscape::Trace::Potrace::PotraceTracingEngine *engine =
+    //      (Inkscape::Trace::Potrace::PotraceTracingEngine *)userData;
+}
+
+
+namespace {
+ustring twohex( int value )
+{
+    return ustring::format(std::hex, std::setfill(L'0'), std::setw(2), value);
+}
+} // namespace
+
+
+//required by potrace
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Potrace {
+
+
+/**
+ *
+ */
+PotraceTracingEngine::PotraceTracingEngine() :
+    keepGoing(1),
+    traceType(TRACE_BRIGHTNESS),
+    invert(false),
+    quantizationNrColors(8),
+    brightnessThreshold(0.45),
+    brightnessFloor(0),
+    cannyHighThreshold(0.65),
+    multiScanNrColors(8),
+    multiScanStack(true),
+    multiScanSmooth(false),
+    multiScanRemoveBackground(false)
+{
+    /* get default parameters */
+    potraceParams = potrace_param_default();
+    potraceParams->progress.callback = potraceStatusCallback;
+    potraceParams->progress.data = (void *)this;
+}
+
+PotraceTracingEngine::PotraceTracingEngine(TraceType traceType, bool invert, int quantizationNrColors, double brightnessThreshold, double brightnessFloor, double cannyHighThreshold, int multiScanNrColors, bool multiScanStack, bool multiScanSmooth, bool multiScanRemoveBackground) :
+  keepGoing(1), traceType(traceType), invert(invert), quantizationNrColors(quantizationNrColors), brightnessThreshold(brightnessThreshold), brightnessFloor(brightnessFloor), cannyHighThreshold(cannyHighThreshold), multiScanNrColors(multiScanNrColors) , multiScanStack(multiScanStack), multiScanSmooth(multiScanSmooth), multiScanRemoveBackground(multiScanRemoveBackground)
+{
+    potraceParams = potrace_param_default();
+    potraceParams->progress.callback = potraceStatusCallback;
+    potraceParams->progress.data = (void *)this;
+}
+
+
+PotraceTracingEngine::~PotraceTracingEngine()
+{
+    potrace_param_free(potraceParams);
+}
+
+
+
+
+struct Point
+{
+    double x;
+    double y;
+};
+
+
+/**
+ * Check a point against a list of points to see if it
+ * has already occurred.
+ */
+static bool hasPoint(std::vector<Point> &points, double x, double y)
+{
+    for (auto p : points)
+        {
+        if (p.x == x && p.y == y)
+            return true;
+        }
+    return false;
+}
+
+
+/**
+ *  Recursively descend the potrace_path_t node tree, writing paths in SVG
+ *  format into the output stream.  The Point vector is used to prevent
+ *  redundant paths.  Returns number of paths processed.
+ */
+static long writePaths(PotraceTracingEngine *engine, potrace_path_t *plist,
+           Inkscape::SVG::PathString& data, std::vector<Point> &points)
+{
+    long nodeCount = 0L;
+
+    potrace_path_t *node;
+    for (node=plist; node ; node=node->sibling)
+        {
+        potrace_curve_t *curve = &(node->curve);
+        //g_message("node->fm:%d\n", node->fm);
+        if (!curve->n)
+            continue;
+        const potrace_dpoint_t *pt = curve->c[curve->n - 1];
+        double x0 = 0.0;
+        double y0 = 0.0;
+        double x1 = 0.0;
+        double y1 = 0.0;
+        double x2 = pt[2].x;
+        double y2 = pt[2].y;
+        //Have we been here already?
+        if (hasPoint(points, x2, y2))
+            {
+            //g_message("duplicate point: (%f,%f)\n", x2, y2);
+            continue;
+            }
+        else
+            {
+            Point p;
+            p.x = x2; p.y = y2;
+            points.push_back(p);
+            }
+        data.moveTo(x2, y2);
+        nodeCount++;
+
+        for (int i=0 ; i<curve->n ; i++)
+            {
+            if (!engine->keepGoing)
+                return 0L;
+            pt = curve->c[i];
+            x0 = pt[0].x;
+            y0 = pt[0].y;
+            x1 = pt[1].x;
+            y1 = pt[1].y;
+            x2 = pt[2].x;
+            y2 = pt[2].y;
+            switch (curve->tag[i])
+                {
+                case POTRACE_CORNER:
+                    data.lineTo(x1, y1).lineTo(x2, y2);
+                break;
+                case POTRACE_CURVETO:
+                    data.curveTo(x0, y0, x1, y1, x2, y2);
+                break;
+                default:
+                break;
+                }
+            nodeCount++;
+            }
+        data.closePath();
+
+        for (potrace_path_t *child=node->childlist; child ; child=child->sibling)
+            {
+            nodeCount += writePaths(engine, child, data, points);
+            }
+        }
+
+    return nodeCount;
+
+}
+
+
+static GrayMap *filter(PotraceTracingEngine &engine, GdkPixbuf * pixbuf)
+{
+    if (!pixbuf)
+        return nullptr;
+
+    GrayMap *newGm = nullptr;
+
+    /*### Color quantization -- banding ###*/
+    if (engine.traceType == TRACE_QUANT)
+        {
+        RgbMap *rgbmap = gdkPixbufToRgbMap(pixbuf);
+        if (!rgbmap)
+            return nullptr;
+        //rgbMap->writePPM(rgbMap, "rgb.ppm");
+        newGm = quantizeBand(rgbmap,
+                            engine.quantizationNrColors);
+        rgbmap->destroy(rgbmap);
+        //return newGm;
+        }
+
+    /*### Brightness threshold ###*/
+    else if ( engine.traceType == TRACE_BRIGHTNESS ||
+              engine.traceType == TRACE_BRIGHTNESS_MULTI )
+        {
+        GrayMap *gm = gdkPixbufToGrayMap(pixbuf);
+        if (!gm)
+            return nullptr;
+
+        newGm = GrayMapCreate(gm->width, gm->height);
+        if (!newGm)
+            {
+            gm->destroy(gm);
+            return nullptr;
+            }
+        double floor =  3.0 *
+               ( engine.brightnessFloor * 256.0 );
+        double cutoff =  3.0 *
+               ( engine.brightnessThreshold * 256.0 );
+        for (int y=0 ; y<gm->height ; y++)
+            {
+            for (int x=0 ; x<gm->width ; x++)
+                {
+                double brightness = (double)gm->getPixel(gm, x, y);
+                if (brightness >= floor && brightness < cutoff)
+                    newGm->setPixel(newGm, x, y, GRAYMAP_BLACK);  //black pixel
+                else
+                    newGm->setPixel(newGm, x, y, GRAYMAP_WHITE); //white pixel
+                }
+            }
+
+        gm->destroy(gm);
+        //newGm->writePPM(newGm, "brightness.ppm");
+        //return newGm;
+        }
+
+    /*### Canny edge detection ###*/
+    else if (engine.traceType == TRACE_CANNY)
+        {
+        GrayMap *gm = gdkPixbufToGrayMap(pixbuf);
+        if (!gm)
+            return nullptr;
+        newGm = grayMapCanny(gm, 0.1, engine.cannyHighThreshold);
+        gm->destroy(gm);
+        //newGm->writePPM(newGm, "canny.ppm");
+        //return newGm;
+        }
+
+    /*### Do I invert the image? ###*/
+    if (newGm && engine.invert)
+        {
+        for (int y=0 ; y<newGm->height ; y++)
+            {
+            for (int x=0 ; x<newGm->width ; x++)
+                {
+                unsigned long brightness = newGm->getPixel(newGm, x, y);
+                brightness = 765 - brightness;
+                newGm->setPixel(newGm, x, y, brightness);
+                }
+            }
+        }
+
+    return newGm;//none of the above
+}
+
+
+static IndexedMap *filterIndexed(PotraceTracingEngine &engine, GdkPixbuf * pixbuf)
+{
+    if (!pixbuf)
+        return nullptr;
+
+    IndexedMap *newGm = nullptr;
+
+    RgbMap *gm = gdkPixbufToRgbMap(pixbuf);
+    if (!gm)
+        return nullptr;
+    if (engine.multiScanSmooth)
+        {
+        RgbMap *gaussMap = rgbMapGaussian(gm);
+        newGm = rgbMapQuantize(gaussMap, engine.multiScanNrColors);
+        gaussMap->destroy(gaussMap);
+        }
+    else
+        {
+        newGm = rgbMapQuantize(gm, engine.multiScanNrColors);
+        }
+    gm->destroy(gm);
+
+    if (newGm && (engine.traceType == TRACE_QUANT_MONO || engine.traceType == TRACE_BRIGHTNESS_MULTI))
+        {
+        //Turn to grays
+        for (int i=0 ; i<newGm->nrColors ; i++)
+            {
+            RGB rgb = newGm->clut[i];
+            int grayVal = (rgb.r + rgb.g + rgb.b) / 3;
+            rgb.r = rgb.g = rgb.b = grayVal;
+            newGm->clut[i] = rgb;
+            }
+        }
+
+    return newGm;
+}
+
+
+
+
+Glib::RefPtr<Gdk::Pixbuf> 
+PotraceTracingEngine::preview(Glib::RefPtr<Gdk::Pixbuf> thePixbuf)
+{
+    GdkPixbuf *pixbuf = thePixbuf->gobj();
+
+    if ( traceType == TRACE_QUANT_COLOR ||
+         traceType == TRACE_QUANT_MONO  ||
+         traceType == TRACE_BRIGHTNESS_MULTI) /* this is a lie: multipass doesn't use filterIndexed, but it's a better preview approx than filter() */
+    {
+        IndexedMap *gm = filterIndexed(*this, pixbuf);
+        if (!gm)
+            return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+
+        Glib::RefPtr<Gdk::Pixbuf> newBuf =
+             Glib::wrap(indexedMapToGdkPixbuf(gm), false);
+
+        gm->destroy(gm);
+
+        return newBuf;
+        }
+    else
+        {
+        GrayMap *gm = filter(*this, pixbuf);
+        if (!gm)
+            return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+
+        Glib::RefPtr<Gdk::Pixbuf> newBuf =
+            Glib::wrap(grayMapToGdkPixbuf(gm), false);
+
+        gm->destroy(gm);
+
+        return newBuf;
+        }
+}
+
+
+//*This is the core inkscape-to-potrace binding
+std::string PotraceTracingEngine::grayMapToPath(GrayMap *grayMap, long *nodeCount)
+{
+    if (!keepGoing)
+    {
+        g_warning("aborted");
+        return "";
+    }
+
+    potrace_bitmap_t *potraceBitmap = bm_new(grayMap->width, grayMap->height);
+    if (!potraceBitmap)
+    {
+        return "";
+    }
+    bm_clear(potraceBitmap, 0);
+
+    //##Read the data out of the GrayMap
+    for (int y=0 ; y<grayMap->height ; y++)
+        {
+        for (int x=0 ; x<grayMap->width ; x++)
+            {
+            BM_UPUT(potraceBitmap, x, y,
+                  grayMap->getPixel(grayMap, x, y) ? 0 : 1);
+            }
+        }
+
+    //##Debug
+    /*
+    FILE *f = fopen("poimage.pbm", "wb");
+    bm_writepbm(f, bm);
+    fclose(f);
+    */
+
+    /* trace a bitmap*/
+    potrace_state_t *potraceState = potrace_trace(potraceParams,
+                                                  potraceBitmap);
+
+    //## Free the Potrace bitmap
+    bm_free(potraceBitmap);
+
+    if (!keepGoing)
+        {
+        g_warning("aborted");
+        potrace_state_free(potraceState);
+        return "";
+        }
+
+    Inkscape::SVG::PathString data;
+
+    //## copy the path information into our d="" attribute string
+    std::vector<Point> points;
+    long thisNodeCount = writePaths(this, potraceState->plist, data, points);
+
+    /* free a potrace items */
+    potrace_state_free(potraceState);
+
+    if (!keepGoing)
+        return "";
+
+    if ( nodeCount)
+        *nodeCount = thisNodeCount;
+
+    return data.string();
+}
+
+
+
+/**
+ *  This is called for a single scan
+ */
+std::vector<TracingEngineResult> PotraceTracingEngine::traceSingle(GdkPixbuf * thePixbuf)
+{
+
+    std::vector<TracingEngineResult> results;
+
+    if (!thePixbuf)
+        return results;
+
+    brightnessFloor = 0.0; //important to set this
+
+    GrayMap *grayMap = filter(*this, thePixbuf);
+    if (!grayMap)
+        return results;
+
+    long nodeCount = 0L;
+    std::string d = grayMapToPath(grayMap, &nodeCount);
+
+    grayMap->destroy(grayMap);
+
+    char const *style = "fill:#000000";
+
+    //g_message("### GOT '%s' \n", d);
+    TracingEngineResult result(style, d, nodeCount);
+    results.push_back(result);
+
+    return results;
+}
+
+
+/**
+ *  This allows routines that already generate GrayMaps to skip image filtering,
+ *  increasing performance.
+ */
+std::vector<TracingEngineResult> PotraceTracingEngine::traceGrayMap(GrayMap *grayMap)
+{
+
+    std::vector<TracingEngineResult> results;
+
+    brightnessFloor = 0.0; //important to set this
+
+    long nodeCount = 0L;
+    std::string d = grayMapToPath(grayMap, &nodeCount);
+
+    char const *style = "fill:#000000";
+
+    //g_message("### GOT '%s' \n", d);
+    TracingEngineResult result(style, d, nodeCount);
+    results.push_back(result);
+
+    return results;
+}
+
+/**
+ *  Called for multiple-scanning algorithms
+ */
+std::vector<TracingEngineResult> PotraceTracingEngine::traceBrightnessMulti(GdkPixbuf * thePixbuf)
+{
+    std::vector<TracingEngineResult> results;
+
+    if ( thePixbuf ) {
+        double low     = 0.2; //bottom of range
+        double high    = 0.9; //top of range
+        double delta   = (high - low ) / ((double)multiScanNrColors);
+
+        brightnessFloor = 0.0; //Set bottom to black
+
+        int traceCount = 0;
+
+        for ( brightnessThreshold = low ;
+              brightnessThreshold <= high ;
+              brightnessThreshold += delta) {
+            GrayMap *grayMap = filter(*this, thePixbuf);
+            if ( grayMap ) {
+                long nodeCount = 0L;
+                std::string d = grayMapToPath(grayMap, &nodeCount);
+
+                grayMap->destroy(grayMap);
+
+                if ( !d.empty() ) {
+                    //### get style info
+                    int grayVal = (int)(256.0 * brightnessThreshold);
+                    ustring style = ustring::compose("fill-opacity:1.0;fill:#%1%2%3", twohex(grayVal), twohex(grayVal), twohex(grayVal) );
+
+                    //g_message("### GOT '%s' \n", style.c_str());
+                    TracingEngineResult result(style.raw(), d, nodeCount);
+                    results.push_back(result);
+
+                    if (!multiScanStack) {
+                        brightnessFloor = brightnessThreshold;
+                    }
+
+                    SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+                    if (desktop) {
+                        ustring msg = ustring::compose(_("Trace: %1.  %2 nodes"), traceCount++, nodeCount);
+                        desktop->getMessageStack()->flash(Inkscape::NORMAL_MESSAGE, msg);
+                    }
+                }
+            }
+        }
+
+        //# Remove the bottom-most scan, if requested
+        if (results.size() > 1 && multiScanRemoveBackground) {
+            results.erase(results.end() - 1);
+        }
+    }
+
+    return results;
+}
+
+
+/**
+ *  Quantization
+ */
+std::vector<TracingEngineResult> PotraceTracingEngine::traceQuant(GdkPixbuf * thePixbuf)
+{
+    std::vector<TracingEngineResult> results;
+
+    if (thePixbuf) {
+        IndexedMap *iMap = filterIndexed(*this, thePixbuf);
+        if ( iMap ) {
+            //Create and clear a gray map
+            GrayMap *gm = GrayMapCreate(iMap->width, iMap->height);
+            for (int row=0 ; row<gm->height ; row++) {
+                for (int col=0 ; col<gm->width ; col++) {
+                    gm->setPixel(gm, col, row, GRAYMAP_WHITE);
+                }
+            }
+
+            for (int colorIndex=0 ; colorIndex<iMap->nrColors ; colorIndex++) {
+                // Make a gray map for each color index
+                for (int row=0 ; row<iMap->height ; row++) {
+                    for (int col=0 ; col<iMap->width ; col++) {
+                        int indx = (int) iMap->getPixel(iMap, col, row);
+                        if (indx == colorIndex) {
+                            gm->setPixel(gm, col, row, GRAYMAP_BLACK); //black
+                        } else if (!multiScanStack) {
+                            gm->setPixel(gm, col, row, GRAYMAP_WHITE); //white
+                        }
+                    }
+                }
+
+                //## Now we have a traceable graymap
+                long nodeCount = 0L;
+                std::string d = grayMapToPath(gm, &nodeCount);
+
+                if ( !d.empty() ) {
+                    //### get style info
+                    RGB rgb = iMap->clut[colorIndex];
+                    ustring style = ustring::compose("fill:#%1%2%3", twohex(rgb.r), twohex(rgb.g), twohex(rgb.b) );
+
+                    //g_message("### GOT '%s' \n", style.c_str());
+                    TracingEngineResult result(style.raw(), d, nodeCount);
+                    results.push_back(result);
+
+                    SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+                    if (desktop) {
+                        ustring msg = ustring::compose(_("Trace: %1.  %2 nodes"), colorIndex, nodeCount);
+                        desktop->getMessageStack()->flash(Inkscape::NORMAL_MESSAGE, msg);
+                    }
+                }
+            }// for colorIndex
+
+            gm->destroy(gm);
+            iMap->destroy(iMap);
+        }
+
+        //# Remove the bottom-most scan, if requested
+        if (results.size() > 1 && multiScanRemoveBackground) {
+            results.erase(results.end() - 1);
+        }
+    }
+
+    return results;
+}
+
+
+/**
+ *  This is the working method of this interface, and all
+ *  implementing classes.  Take a GdkPixbuf, trace it, and
+ *  return the path data that is compatible with the d="" attribute
+ *  of an SVG <path> element.
+ */
+std::vector<TracingEngineResult>
+PotraceTracingEngine::trace(Glib::RefPtr<Gdk::Pixbuf> pixbuf)
+{
+
+    GdkPixbuf *thePixbuf = pixbuf->gobj();
+
+    //Set up for messages
+    keepGoing             = 1;
+
+    if ( traceType == TRACE_QUANT_COLOR ||
+         traceType == TRACE_QUANT_MONO   )
+        {
+        return traceQuant(thePixbuf);
+        }
+    else if ( traceType == TRACE_BRIGHTNESS_MULTI )
+        {
+        return traceBrightnessMulti(thePixbuf);
+        }
+    else
+        {
+        return traceSingle(thePixbuf);
+        }
+}
+
+
+/**
+ *  Abort the thread that is executing getPathDataFromPixbuf()
+ */
+void PotraceTracingEngine::abort()
+{
+    //g_message("PotraceTracingEngine::abort()\n");
+    keepGoing = 0;
+}
+
+
+
+
+}  // namespace Potrace
+}  // namespace Trace
+}  // namespace Inkscape
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/potrace/inkscape-potrace.h b/src/trace/potrace/inkscape-potrace.h
new file mode 100644
index 0000000..c4c7bf4
--- /dev/null
+++ b/src/trace/potrace/inkscape-potrace.h
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This is the C++ glue between Inkscape and Potrace
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2004-2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ * Potrace, the wonderful tracer located at http://potrace.sourceforge.net,
+ * is provided by the generosity of Peter Selinger, to whom we are grateful.
+ *
+ */
+
+#ifndef __INKSCAPE_POTRACE_H__
+#define __INKSCAPE_POTRACE_H__
+
+#include <trace/trace.h>
+#include <potracelib.h>
+
+struct GrayMap_def;
+typedef GrayMap_def GrayMap;
+
+namespace Inkscape {
+
+namespace Trace {
+
+namespace Potrace {
+
+enum TraceType
+    {
+    TRACE_BRIGHTNESS,
+    TRACE_BRIGHTNESS_MULTI,
+    TRACE_CANNY,
+    TRACE_QUANT,
+    TRACE_QUANT_COLOR,
+    TRACE_QUANT_MONO,
+    // Used in tradedialog.cpp
+    AUTOTRACE_SINGLE,
+    AUTOTRACE_MULTI,
+    AUTOTRACE_CENTERLINE
+    };
+
+
+class PotraceTracingEngine : public TracingEngine
+{
+
+    public:
+
+    /**
+     *
+     */
+    PotraceTracingEngine();
+    PotraceTracingEngine(TraceType traceType, bool invert, int quantizationNrColors, double brightnessThreshold, double brightnessFloor, double cannyHighThreshold, int multiScanNrColors, bool multiScanStack, bool multiScanSmooth, bool multiScanRemoveBackground);
+
+    /**
+     *
+     */
+    ~PotraceTracingEngine() override;
+
+    /**
+     *  This is the working method of this implementing class, and all
+     *  implementing classes.  Take a GdkPixbuf, trace it, and
+     *  return the path data that is compatible with the d="" attribute
+     *  of an SVG <path> element.
+     */
+    std::vector<TracingEngineResult> trace(
+                        Glib::RefPtr<Gdk::Pixbuf> pixbuf) override;
+
+    /**
+     *  Abort the thread that is executing getPathDataFromPixbuf()
+     */
+    void abort() override;
+
+    /**
+     *
+     */
+    Glib::RefPtr<Gdk::Pixbuf> preview(Glib::RefPtr<Gdk::Pixbuf> pixbuf);
+
+    /**
+     *
+     */
+    int keepGoing;
+
+    std::vector<TracingEngineResult>traceGrayMap(GrayMap *grayMap);
+
+    potrace_param_t *potraceParams;
+    TraceType traceType;
+
+    //## do I invert at the end?
+    bool invert;
+
+    //## Color-->b&w quantization
+    int quantizationNrColors;
+
+    //## brightness items
+    double brightnessThreshold;
+    double brightnessFloor; //usually 0.0
+
+    //## canny items
+    double cannyHighThreshold;
+
+    //## Color-->multiscan quantization
+    int multiScanNrColors;
+    bool multiScanStack; //do we tile or stack?
+    bool multiScanSmooth;//do we use gaussian filter?
+    bool multiScanRemoveBackground; //do we remove the bottom trace?
+    
+    private:
+    /**
+     * This is the actual wrapper of the call to Potrace.  nodeCount
+     * returns the count of nodes created.  May be NULL if ignored.
+     */
+    std::string grayMapToPath(GrayMap *gm, long *nodeCount);
+
+    std::vector<TracingEngineResult>traceBrightnessMulti(GdkPixbuf *pixbuf);
+    std::vector<TracingEngineResult>traceQuant(GdkPixbuf *pixbuf);
+    std::vector<TracingEngineResult>traceSingle(GdkPixbuf *pixbuf);
+
+
+};//class PotraceTracingEngine
+
+
+
+}  // namespace Potrace
+}  // namespace Trace
+}  // namespace Inkscape
+
+
+#endif  //__INKSCAPE_POTRACE_H__
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
diff --git a/src/trace/quantize.cpp b/src/trace/quantize.cpp
new file mode 100644
index 0000000..228cb47
--- /dev/null
+++ b/src/trace/quantize.cpp
@@ -0,0 +1,599 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Quantization for Inkscape
+ *
+ * Authors:
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+#include <new>
+#include <glib.h>
+
+#include "pool.h"
+#include "imagemap.h"
+#include "quantize.h"
+
+typedef struct Ocnode_def Ocnode;
+
+/**
+ * an octree node datastructure
+ */
+struct Ocnode_def
+{
+    Ocnode *parent;           // parent node
+    Ocnode **ref;             // node's reference
+    Ocnode *child[8];         // children
+    int nchild;               // number of children
+    int width;                // width level of this node
+    RGB rgb;                  // rgb's prefix of that node
+    unsigned long weight;     // number of pixels this node accounts for
+    unsigned long rs, gs, bs; // sum of pixels colors this node accounts for
+    int nleaf;                // number of leaves under this node
+    unsigned long mi;         // minimum impact
+};
+
+/*
+-- algorithm principle:
+
+- inspired by the octree method, we associate a tree to a given color map
+
+- nodes in those trees have this shape:
+
+                                parent
+                                   |
+        color_prefix(stored in rgb):width
+     colors_sum(stored in rs,gs,bs)/weight
+         /               |               \
+     child1           child2           child3
+
+- (grayscale) trees associated to pixels with colors 87 = 0b1010111 and
+  69 = 0b1000101 are:
+
+           .                 .    <-- roots of the trees
+           |                 |
+    1010111:0  and    1000101:0   <-- color prefixes, written in binary form
+         87/1              69/1   <-- color sums, written in decimal form
+
+- the result of merging the two trees is:
+
+                   .
+                   |
+                 10:5       <----- longest common prefix and binary width
+                156/2       <---.  of the covered color range.
+            /            \      |
+    1000101:0      1010111:0    '- sum of colors and quantity of pixels
+         69/1           87/1       this node accounts for
+
+  one should consider three cases when two trees are to be merged:
+  - one tree range is included in the range of the other one, and the first
+    tree has to be inserted as a child (or merged with the corresponding
+    child) of the other.
+  - their ranges are the same, and their children have to be merged under
+    a single root.
+  - ranges have no intersection, and a fork node has to be created (like in
+    the given example).
+
+- a tree for an image is built dividing the image in 2 parts and merging
+  the trees obtained recursively for the two parts. a tree for a one pixel
+  part is a leaf like one of those which were given above.
+
+- last, this tree is reduced a specified number of leaves, deleting first
+  leaves with minimal impact i.e. [ weight * 2^(2*parentwidth) ] value :
+  a fair approximation of the impact a leaf removal would have on the final
+  result : it's the corresponding covered area times the square of the
+  introduced color distance.
+
+  deletion of a node A below a node with only two children is done as
+  follows :
+
+  - when the brother is a leaf, the brother is deleted as well, both nodes
+    are then represented by their father.
+
+     |               |
+     .       ==>     .
+    / \
+   A   .
+
+  - otherwise the deletion of A deletes also his father, which plays no
+    role anymore:
+
+     |                |
+     .       ==>       \
+    / \                 |
+   A   .                .
+      / \              / \
+
+  in that way, every leaf removal operation really decreases the remaining
+  total number of leaves by one.
+
+- very last, color indexes are attributed to leaves; associated colors are
+  averages, computed from weight and color components sums.
+
+-- improvements to the usual octree method:
+
+- since this algorithm shall often be used to perform quantization using a
+  very low (2-16) set of colors and not with a usual 256 value, we choose
+  more carefully which nodes are to be deleted.
+
+- depth of leaves is not fixed to an arbitrary number (which should be 8
+  when color components are in 0-255), so there is no need to go down to a
+  depth of 8 for each pixel (at full precision), unless it is really
+  required.
+
+- tree merging also fastens the overall tree building, and intermediate
+  processing could be done.
+
+- a huge optimization against the stupid removal algorithm (i.e. find a best
+  match over the whole tree, remove it and do it again) was implemented:
+  nodes are marked with the minimal impact of the removal of a leaf below
+  it. we proceed to the removal recursively. we stop when current removal
+  level is above the current node minimal, otherwise reached leaves are
+  removed, and every change over minimal impacts is propagated back to the
+  whole tree when the recursion ends.
+
+-- specific optimizations
+
+- pool allocation is used to allocate nodes (increased performance on large
+  images).
+
+*/
+
+inline RGB operator>>(RGB rgb, int s)
+{
+  RGB res;
+  res.r = rgb.r >> s; res.g = rgb.g >> s; res.b = rgb.b >> s;
+  return res;
+}
+inline bool operator==(RGB rgb1, RGB rgb2)
+{
+  return (rgb1.r == rgb2.r && rgb1.g == rgb2.g && rgb1.b == rgb2.b);
+}
+
+inline int childIndex(RGB rgb)
+{
+    return (((rgb.r)&1)<<2) | (((rgb.g)&1)<<1) | (((rgb.b)&1));
+}
+
+/**
+ * allocate a new node
+ */
+inline Ocnode *ocnodeNew(pool<Ocnode> *pool)
+{
+    Ocnode *node = pool->draw();
+    node->ref = nullptr;
+    node->parent = nullptr;
+    node->nchild = 0;
+    for (auto & i : node->child) i = nullptr;
+    node->mi = 0;
+    return node;
+}
+
+inline void ocnodeFree(pool<Ocnode> *pool, Ocnode *node) {
+    pool->drop(node);
+}
+
+
+/**
+ * free a full octree
+ */
+static void octreeDelete(pool<Ocnode> *pool, Ocnode *node)
+{
+    if (!node) return;
+    for (auto & i : node->child)
+        octreeDelete(pool, i);
+    ocnodeFree(pool, node);
+}
+
+/**
+ *  pretty-print an octree, debugging purposes
+ */
+#if 0
+static void ocnodePrint(Ocnode *node, int indent)
+{
+    if (!node) return;
+    printf("width:%d weight:%lu rgb:%6x nleaf:%d mi:%lu\n",
+           node->width,
+           node->weight,
+           (unsigned int)(
+           ((node->rs / node->weight) << 16) +
+           ((node->gs / node->weight) << 8) +
+           (node->bs / node->weight)),
+           node->nleaf,
+           node->mi
+           );
+    for (int i = 0; i < 8; i++) if (node->child[i])
+        {
+        for (int k = 0; k < indent; k++) printf(" ");//indentation
+        printf("[%d:%p] ", i, node->child[i]);
+        ocnodePrint(node->child[i], indent+2);
+        }
+}
+
+void octreePrint(Ocnode *node)
+{
+    printf("<<octree>>\n");
+    if (node) printf("[r:%p] ", node); ocnodePrint(node, 2);
+}
+#endif
+
+/**
+ * builds a single <rgb> color leaf at location <ref>
+ */
+static void ocnodeLeaf(pool<Ocnode> *pool, Ocnode **ref, RGB rgb)
+{
+    assert(ref);
+    Ocnode *node = ocnodeNew(pool);
+    node->width = 0;
+    node->rgb = rgb;
+    node->rs = rgb.r; node->gs = rgb.g; node->bs = rgb.b;
+    node->weight = 1;
+    node->nleaf = 1;
+    node->mi = 0;
+    node->ref = ref;
+    *ref = node;
+}
+
+/**
+ *  merge nodes <node1> and <node2> at location <ref> with parent <parent>
+ */
+static int octreeMerge(pool<Ocnode> *pool, Ocnode *parent, Ocnode **ref, Ocnode *node1, Ocnode *node2)
+{
+    assert(ref);
+    if (!node1 && !node2) return 0;
+    assert(node1 != node2);
+    if (parent && !*ref) parent->nchild++;
+    if (!node1)
+        {
+        *ref = node2; node2->ref = ref; node2->parent = parent;
+        return node2->nleaf;
+        }
+    if (!node2)
+        {
+        *ref = node1; node1->ref = ref; node1->parent = parent;
+        return node1->nleaf;
+        }
+    int dwitdth = node1->width - node2->width;
+    if (dwitdth > 0 && node1->rgb == node2->rgb >> dwitdth)
+        {
+        //place node2 below node1
+        { *ref = node1; node1->ref = ref; node1->parent = parent; }
+        int i = childIndex(node2->rgb >> (dwitdth - 1));
+        node1->rs += node2->rs; node1->gs += node2->gs; node1->bs += node2->bs;
+        node1->weight += node2->weight;
+	node1->mi = 0;
+        if (node1->child[i]) node1->nleaf -= node1->child[i]->nleaf;
+        node1->nleaf +=
+          octreeMerge(pool, node1, &node1->child[i], node1->child[i], node2);
+        return node1->nleaf;
+        }
+    else if (dwitdth < 0 && node2->rgb == node1->rgb >> (-dwitdth))
+        {
+        //place node1 below node2
+        { *ref = node2; node2->ref = ref; node2->parent = parent; }
+        int i = childIndex(node1->rgb >> (-dwitdth - 1));
+        node2->rs += node1->rs; node2->gs += node1->gs; node2->bs += node1->bs;
+        node2->weight += node1->weight;
+	node2->mi = 0;
+        if (node2->child[i]) node2->nleaf -= node2->child[i]->nleaf;
+        node2->nleaf +=
+          octreeMerge(pool, node2, &node2->child[i], node2->child[i], node1);
+        return node2->nleaf;
+        }
+    else
+        {
+        //nodes have either no intersection or the same root
+        Ocnode *newnode;
+        newnode = ocnodeNew(pool);
+        newnode->rs = node1->rs + node2->rs;
+        newnode->gs = node1->gs + node2->gs;
+        newnode->bs = node1->bs + node2->bs;
+        newnode->weight = node1->weight + node2->weight;
+        { *ref = newnode; newnode->ref = ref; newnode->parent = parent; }
+        if (dwitdth == 0 && node1->rgb == node2->rgb)
+            {
+            //merge the nodes in <newnode>
+            newnode->width = node1->width; // == node2->width
+            newnode->rgb = node1->rgb;     // == node2->rgb
+            newnode->nchild = 0;
+            newnode->nleaf = 0;
+            if (node1->nchild == 0 && node2->nchild == 0)
+                newnode->nleaf = 1;
+            else
+                for (int i = 0; i < 8; i++)
+		  if (node1->child[i] || node2->child[i])
+                    newnode->nleaf +=
+		      octreeMerge(pool, newnode, &newnode->child[i],
+				  node1->child[i], node2->child[i]);
+            ocnodeFree(pool, node1); ocnodeFree(pool, node2);
+            return newnode->nleaf;
+            }
+        else
+            {
+            //use <newnode> as a fork node with children <node1> and <node2>
+            int newwidth =
+              node1->width > node2->width ? node1->width : node2->width;
+            RGB rgb1 = node1->rgb >> (newwidth - node1->width);
+            RGB rgb2 = node2->rgb >> (newwidth - node2->width);
+            //according to the previous tests <rgb1> != <rgb2> before the loop
+            while (!(rgb1 == rgb2))
+              { rgb1 = rgb1 >> 1; rgb2 = rgb2 >> 1; newwidth++; };
+            newnode->width = newwidth;
+            newnode->rgb = rgb1;  // == rgb2
+            newnode->nchild = 2;
+            newnode->nleaf = node1->nleaf + node2->nleaf;
+            int i1 = childIndex(node1->rgb >> (newwidth - node1->width - 1));
+            int i2 = childIndex(node2->rgb >> (newwidth - node2->width - 1));
+            node1->parent = newnode;
+            node1->ref = &newnode->child[i1];
+            newnode->child[i1] = node1;
+            node2->parent = newnode;
+            node2->ref = &newnode->child[i2];
+            newnode->child[i2] = node2;
+            return newnode->nleaf;
+            }
+        }
+}
+
+/**
+ * upatade mi value for leaves
+ */
+static inline void ocnodeMi(Ocnode *node)
+{
+    node->mi = node->parent ?
+       node->weight << (2 * node->parent->width) : 0;
+}
+
+/**
+ * remove leaves whose prune impact value is lower than <lvl>. at most
+ * <count> leaves are removed, and <count> is decreased on each removal.
+ * all parameters including minimal impact values are regenerated.
+ */
+static void ocnodeStrip(pool<Ocnode> *pool, Ocnode **ref, int *count, unsigned long lvl)
+{
+    Ocnode *node = *ref;
+    if (!count || !node) return;
+    assert(ref == node->ref);
+    if (node->nchild == 0) // leaf node
+        {
+        if (!node->mi) ocnodeMi(node); //mi generation may be required
+	if (node->mi > lvl) return; //leaf is above strip level
+        ocnodeFree(pool, node);
+        *ref = nullptr;
+        (*count)--;
+        }
+    else
+        {
+	if (node->mi && node->mi > lvl) //node is above strip level
+            return;
+        node->nchild = 0;
+        node->nleaf = 0;
+        node->mi = 0;
+        Ocnode **lonelychild = nullptr;
+        for (auto & i : node->child) if (i)
+            {
+            ocnodeStrip(pool, &i, count, lvl);
+            if (i)
+                {
+                lonelychild = &i;
+                node->nchild++;
+                node->nleaf += i->nleaf;
+                if (!node->mi || node->mi > i->mi)
+                    node->mi = i->mi;
+                }
+            }
+      // tree adjustments
+        if (node->nchild == 0)
+            {
+            (*count)++;
+            node->nleaf = 1;
+	    ocnodeMi(node);
+            }
+        else if (node->nchild == 1)
+            {
+            if ((*lonelychild)->nchild == 0)
+                {
+                //remove the <lonelychild> leaf under a 1 child node
+                node->nchild = 0;
+                node->nleaf = 1;
+		ocnodeMi(node);
+                ocnodeFree(pool, *lonelychild);
+                *lonelychild = nullptr;
+                }
+            else
+                {
+                //make a bridge to <lonelychild> over a 1 child node
+                (*lonelychild)->parent = node->parent;
+                (*lonelychild)->ref = ref;
+                ocnodeFree(pool, node);
+                *ref = *lonelychild;
+                }
+            }
+        }
+}
+
+/**
+ * reduce the leaves of an octree to a given number
+ */
+static void octreePrune(pool<Ocnode> *pool, Ocnode **ref, int ncolor)
+{
+  assert(ref);
+  assert(ncolor > 0);
+  //printf("pruning down to %d colors:\n", ncolor);//debug
+  int n = (*ref)->nleaf - ncolor;
+  if (!*ref || n <= 0) return;
+  while (n > 0)
+      {
+      //printf("removals to go: %10d\t", n);//debug
+      //printf("current prune impact: %10lu\n", (*ref)->mi);//debug
+      //calling strip with global minimum impact of the tree
+      ocnodeStrip(pool, ref, &n, (*ref)->mi);
+      }
+}
+
+/**
+ * build an octree associated to the area of a color map <rgbmap>,
+ * included in the specified (x1,y1)--(x2,y2) rectangle.
+ */
+static void octreeBuildArea(pool<Ocnode> *pool, RgbMap *rgbmap, Ocnode **ref,
+                            int x1, int y1, int x2, int y2, int ncolor)
+{
+    int dx = x2 - x1, dy = y2 - y1;
+    int xm = x1 + dx/2, ym = y1 + dy/2;
+    Ocnode *ref1 = nullptr;
+    Ocnode *ref2 = nullptr;
+    if (dx == 1 && dy == 1)
+        ocnodeLeaf(pool, ref, rgbmap->getPixel(rgbmap, x1, y1));
+    else if (dx > dy)
+        {
+	octreeBuildArea(pool, rgbmap, &ref1, x1, y1, xm, y2, ncolor);
+	octreeBuildArea(pool, rgbmap, &ref2, xm, y1, x2, y2, ncolor);
+	octreeMerge(pool, nullptr, ref, ref1, ref2);
+	}
+    else
+        {
+	octreeBuildArea(pool, rgbmap, &ref1, x1, y1, x2, ym, ncolor);
+	octreeBuildArea(pool, rgbmap, &ref2, x1, ym, x2, y2, ncolor);
+	octreeMerge(pool, nullptr, ref, ref1, ref2);
+	}
+
+    //octreePrune(ref, 2*ncolor);
+    //affects result quality for almost same performance :/
+}
+
+/**
+ * build an octree associated to the <rgbmap> color map,
+ * pruned to <ncolor> colors.
+ */
+static Ocnode *octreeBuild(pool<Ocnode> *pool, RgbMap *rgbmap, int ncolor)
+{
+    //create the octree
+    Ocnode *node = nullptr;
+    octreeBuildArea(pool,
+                    rgbmap, &node,
+                    0, 0, rgbmap->width, rgbmap->height, ncolor
+                    );
+
+    //prune the octree
+    octreePrune(pool, &node, ncolor);
+
+    //octreePrint(node);//debug
+
+    return node;
+}
+
+/**
+ * compute the color palette associated to an octree.
+ */
+static void octreeIndex(Ocnode *node, RGB *rgbpal, int *index)
+{
+    if (!node) return;
+    if (node->nchild == 0)
+        {
+        rgbpal[*index].r = node->rs / node->weight;
+        rgbpal[*index].g = node->gs / node->weight;
+        rgbpal[*index].b = node->bs / node->weight;
+        (*index)++;
+        }
+    else
+        for (auto & i : node->child)
+            if (i)
+                octreeIndex(i, rgbpal, index);
+}
+
+/**
+ * compute the squared distance between two colors
+ */
+static int distRGB(RGB rgb1, RGB rgb2)
+{
+    return
+      (rgb1.r - rgb2.r) * (rgb1.r - rgb2.r)
+    + (rgb1.g - rgb2.g) * (rgb1.g - rgb2.g)
+    + (rgb1.b - rgb2.b) * (rgb1.b - rgb2.b);
+}
+
+/**
+ * find the index of closest color in a palette
+ */
+static int findRGB(RGB *rgbpal, int ncolor, RGB rgb)
+{
+    //assert(ncolor > 0);
+    //assert(rgbpal);
+    int index = -1, dist = 0;
+    for (int k = 0; k < ncolor; k++)
+        {
+        int d = distRGB(rgbpal[k], rgb);
+        if (index == -1 || d < dist) { dist = d; index = k; }
+        }
+    return index;
+}
+
+/**
+ * (qsort) compare two colors for brightness
+ */
+static int compRGB(const void *a, const void *b)
+{
+    RGB *ra = (RGB *)a, *rb = (RGB *)b;
+    return (ra->r + ra->g + ra->b) - (rb->r + rb->g + rb->b);
+}
+
+/**
+ * quantize an RGB image to a reduced number of colors.
+ */
+IndexedMap *rgbMapQuantize(RgbMap *rgbmap, int ncolor)
+{
+    assert(rgbmap);
+    assert(ncolor > 0);
+
+    IndexedMap *newmap = nullptr;
+
+    pool<Ocnode> pool;
+
+    Ocnode *tree = nullptr;
+    try {
+        tree = octreeBuild(&pool, rgbmap, ncolor);
+    }
+    catch (std::bad_alloc &ex) {
+        //should do smthg else?
+        g_warning("rgbMapQuantize: Failed to allocate enough memory to during octreeBuild");
+    }
+
+    if (tree) {
+        RGB *rgbpal = new RGB[ncolor];
+        int indexes = 0;
+        octreeIndex(tree, rgbpal, &indexes);
+
+        octreeDelete(&pool, tree);
+
+        // stacking with increasing contrasts
+        qsort((void *)rgbpal, indexes, sizeof(RGB), compRGB);
+
+        // make the new map
+        newmap = IndexedMapCreate(rgbmap->width, rgbmap->height);
+        if (newmap) {
+            // fill in the color lookup table
+            for (int i = 0; i < indexes; i++) {
+                newmap->clut[i] = rgbpal[i];
+            }
+            newmap->nrColors = indexes;
+
+            // fill in new map pixels
+            for (int y = 0; y < rgbmap->height; y++) {
+                for (int x = 0; x < rgbmap->width; x++) {
+                    RGB rgb = rgbmap->getPixel(rgbmap, x, y);
+                    int index = findRGB(rgbpal, ncolor, rgb);
+                    newmap->setPixel(newmap, x, y, index);
+                }
+            }
+        }
+        delete[] rgbpal;
+    }
+
+    return newmap;
+}
diff --git a/src/trace/quantize.h b/src/trace/quantize.h
new file mode 100644
index 0000000..43942f5
--- /dev/null
+++ b/src/trace/quantize.h
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Quantization for Inkscape
+ *
+ * Authors:
+ *   Stéphane Gimenez <dev@gim.name>
+ *
+ * Copyright (C) 2006 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef __QUANTIZE_H__
+#define __QUANTIZE_H__
+
+#include "imagemap.h"
+
+/**
+ * Quantize an RGB image to a reduced number of colors.
+ */
+IndexedMap *rgbMapQuantize(RgbMap *rgbmap, int nrColors);
+
+#endif /* __QUANTIZE_H__ */
diff --git a/src/trace/siox.cpp b/src/trace/siox.cpp
new file mode 100644
index 0000000..49ecfae
--- /dev/null
+++ b/src/trace/siox.cpp
@@ -0,0 +1,1736 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+   Copyright 2005, 2006 by Gerald Friedland, Kristian Jantz and Lars Knipping
+
+   Conversion to C++ for Inkscape by Bob Jamison
+
+   Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#include "siox.h"
+
+#include <cmath>
+#include <cstdarg>
+#include <map>
+#include <algorithm>
+#include <cstdlib>
+
+
+namespace org
+{
+
+namespace siox
+{
+
+
+
+//########################################################################
+//#  C L A B
+//########################################################################
+
+/**
+ * Convert integer A, R, G, B values into an pixel value.
+ */
+static unsigned long getRGB(int a, int r, int g, int b)
+{
+    if (a<0)  a=0;
+    else if (a>255) a=255;
+
+    if (r<0) r=0;
+    else if (r>255) r=255;
+
+    if (g<0) g=0;
+    else if (g>255) g=255;
+
+    if (b<0) b=0;
+    else if (b>255) b=255;
+
+    return (a<<24)|(r<<16)|(g<<8)|b;
+}
+
+
+
+/**
+ * Convert float A, R, G, B values (0.0-1.0) into an pixel value.
+ */
+static unsigned long getRGB(float a, float r, float g, float b)
+{
+    return getRGB((int)(a * 256.0),
+                  (int)(r * 256.0),
+                  (int)(g * 256.0),
+                  (int)(b * 256.0));
+}
+
+
+
+//#########################################
+//# Root approximations for large speedup.
+//# By njh!
+//#########################################
+static const int ROOT_TAB_SIZE = 16;
+static float cbrt_table[ROOT_TAB_SIZE +1];
+
+double CieLab::cbrt(double x)
+{
+    double y = cbrt_table[int(x*ROOT_TAB_SIZE )]; // assuming x \in [0, 1]
+    y = (2.0 * y + x/(y*y))/3.0;
+    y = (2.0 * y + x/(y*y))/3.0; // polish twice
+    return y;
+}
+
+static float qn_table[ROOT_TAB_SIZE +1];
+
+double CieLab::qnrt(double x)
+{
+    double y = qn_table[int(x*ROOT_TAB_SIZE )]; // assuming x \in [0, 1]
+    double Y = y*y;
+    y = (4.0*y + x/(Y*Y))/5.0;
+    Y = y*y;
+    y = (4.0*y + x/(Y*Y))/5.0; // polish twice
+    return y;
+}
+
+double CieLab::pow24(double x)
+{
+    double onetwo = x*qnrt(x);
+    return onetwo*onetwo;
+}
+
+
+static bool _clab_inited_ = false;
+void CieLab::init()
+{
+    if (!_clab_inited_)
+        {
+        cbrt_table[0] = pow(float(1)/float(ROOT_TAB_SIZE*2), 0.3333);
+        qn_table[0]   = pow(float(1)/float(ROOT_TAB_SIZE*2), 0.2);
+        for(int i = 1; i < ROOT_TAB_SIZE +1; i++)
+            {
+            cbrt_table[i] = pow(float(i)/float(ROOT_TAB_SIZE), 0.3333);
+            qn_table[i] = pow(float(i)/float(ROOT_TAB_SIZE), 0.2);
+            }
+        _clab_inited_ = true;
+        }
+}
+
+
+
+/**
+ * Construct this CieLab from an ARGB value
+ */
+CieLab::CieLab(unsigned long rgb)
+{
+    init();
+
+    int ir  = (rgb>>16) & 0xff;
+    int ig  = (rgb>> 8) & 0xff;
+    int ib  = (rgb    ) & 0xff;
+
+    float fr = ((float)ir) / 255.0;
+    float fg = ((float)ig) / 255.0;
+    float fb = ((float)ib) / 255.0;
+
+    //printf("fr:%f fg:%f fb:%f\n", fr, fg, fb);
+    if (fr > 0.04045)
+        //fr = (float) pow((fr + 0.055) / 1.055, 2.4);
+        fr = (float) pow24((fr + 0.055) / 1.055);
+    else
+        fr = fr / 12.92;
+
+    if (fg > 0.04045)
+        //fg = (float) pow((fg + 0.055) / 1.055, 2.4);
+        fg = (float) pow24((fg + 0.055) / 1.055);
+    else
+        fg = fg / 12.92;
+
+    if (fb > 0.04045)
+        //fb = (float) pow((fb + 0.055) / 1.055, 2.4);
+        fb = (float) pow24((fb + 0.055) / 1.055);
+    else
+        fb = fb / 12.92;
+
+    // Use white = D65
+    const float x = fr * 0.4124 + fg * 0.3576 + fb * 0.1805;
+    const float y = fr * 0.2126 + fg * 0.7152 + fb * 0.0722;
+    const float z = fr * 0.0193 + fg * 0.1192 + fb * 0.9505;
+
+    float vx = x / 0.95047;
+    float vy = y;
+    float vz = z / 1.08883;
+
+    //printf("vx:%f vy:%f vz:%f\n", vx, vy, vz);
+    if (vx > 0.008856)
+        //vx = (float) pow(vx, 0.3333);
+        vx = (float) cbrt(vx);
+    else
+        vx = (7.787 * vx) + (16.0 / 116.0);
+
+    if (vy > 0.008856)
+        //vy = (float) pow(vy, 0.3333);
+        vy = (float) cbrt(vy);
+    else
+        vy = (7.787 * vy) + (16.0 / 116.0);
+
+    if (vz > 0.008856)
+        //vz = (float) pow(vz, 0.3333);
+        vz = (float) cbrt(vz);
+    else
+        vz = (7.787 * vz) + (16.0 / 116.0);
+
+    C = 0;
+    L = 116.0 * vy - 16.0;
+    A = 500.0 * (vx - vy);
+    B = 200.0 * (vy - vz);
+}
+
+
+
+/**
+ * Return this CieLab's value converted to an ARGB value
+ */
+unsigned long CieLab::toRGB()
+{
+    float vy = (L + 16.0) / 116.0;
+    float vx = A / 500.0 + vy;
+    float vz = vy - B / 200.0;
+
+    float vx3 = vx * vx * vx;
+    float vy3 = vy * vy * vy;
+    float vz3 = vz * vz * vz;
+
+    if (vy3 > 0.008856)
+        vy = vy3;
+    else
+        vy = (vy - 16.0 / 116.0) / 7.787;
+
+    if (vx3 > 0.008856)
+        vx = vx3;
+    else
+        vx = (vx - 16.0 / 116.0) / 7.787;
+
+    if (vz3 > 0.008856)
+        vz = vz3;
+    else
+        vz = (vz - 16.0 / 116.0) / 7.787;
+
+    vx *= 0.95047; //use white = D65
+    vz *= 1.08883;
+
+    float vr =(float)(vx *  3.2406 + vy * -1.5372 + vz * -0.4986);
+    float vg =(float)(vx * -0.9689 + vy *  1.8758 + vz *  0.0415);
+    float vb =(float)(vx *  0.0557 + vy * -0.2040 + vz *  1.0570);
+
+    if (vr > 0.0031308)
+        vr = (float)(1.055 * pow(vr, (1.0 / 2.4)) - 0.055);
+    else
+        vr = 12.92 * vr;
+
+    if (vg > 0.0031308)
+        vg = (float)(1.055 * pow(vg, (1.0 / 2.4)) - 0.055);
+    else
+        vg = 12.92 * vg;
+
+    if (vb > 0.0031308)
+        vb = (float)(1.055 * pow(vb, (1.0 / 2.4)) - 0.055);
+    else
+        vb = 12.92 * vb;
+
+    return getRGB(0.0, vr, vg, vb);
+}
+
+
+/**
+ * Squared Euclidean distance between this and another color
+ */
+float CieLab::diffSq(const CieLab &other)
+{
+    float sum=0.0;
+    sum += (L - other.L) * (L - other.L);
+    sum += (A - other.A) * (A - other.A);
+    sum += (B - other.B) * (B - other.B);
+    return sum;
+}
+
+/**
+ * Computes squared euclidean distance in CieLab space for two colors
+ * given as RGB values.
+ */
+float CieLab::diffSq(unsigned int rgb1, unsigned int rgb2)
+{
+    CieLab c1(rgb1);
+    CieLab c2(rgb2);
+    float euclid = c1.diffSq(c2);
+    return euclid;
+}
+
+
+/**
+ * Computes squared euclidean distance in CieLab space for two colors
+ * given as RGB values.
+ */
+float CieLab::diff(unsigned int rgb0, unsigned int rgb1)
+{
+    return (float) sqrt(diffSq(rgb0, rgb1));
+}
+
+
+
+//########################################################################
+//#  T U P E L
+//########################################################################
+
+/**
+ * Helper class for storing the minimum distances to a cluster centroid
+ * in background and foreground and the index to the centroids in each
+ * signature for a given color.
+ */
+class Tupel {
+public:
+
+    Tupel()
+        {
+        minBgDist  = 0.0f;
+        indexMinBg = 0;
+        minFgDist  = 0.0f;
+        indexMinFg = 0;
+        }
+    Tupel(float minBgDistArg, long indexMinBgArg,
+          float minFgDistArg, long indexMinFgArg)
+        {
+        minBgDist  = minBgDistArg;
+        indexMinBg = indexMinBgArg;
+        minFgDist  = minFgDistArg;
+        indexMinFg = indexMinFgArg;
+        }
+    Tupel(const Tupel &other)
+        {
+        minBgDist  = other.minBgDist;
+        indexMinBg = other.indexMinBg;
+        minFgDist  = other.minFgDist;
+        indexMinFg = other.indexMinFg;
+        }
+    Tupel &operator=(const Tupel &other)
+        = default;
+    virtual ~Tupel()
+        = default;
+
+    float minBgDist;
+    long  indexMinBg;
+    float minFgDist;
+    long  indexMinFg;
+
+ };
+
+
+
+//########################################################################
+//#  S I O X    I M A G E
+//########################################################################
+
+/**
+ *  Create an image with the given width and height
+ */
+SioxImage::SioxImage(unsigned int widthArg, unsigned int heightArg)
+{
+    init(widthArg, heightArg);
+}
+
+/**
+ *  Copy constructor
+ */
+SioxImage::SioxImage(const SioxImage &other)
+{
+    pixdata = nullptr;
+    cmdata  = nullptr;
+    assign(other);
+}
+
+/**
+ *  Assignment
+ */
+SioxImage &SioxImage::operator=(const SioxImage &other)
+{
+    assign(other);
+    return *this;
+}
+
+
+/**
+ * Clean up after use.
+ */
+SioxImage::~SioxImage()
+{
+    if (pixdata) delete[] pixdata;
+    if (cmdata)  delete[] cmdata;
+}
+
+/**
+ * Error logging
+ */
+void SioxImage::error(const char *fmt, ...)
+{
+    char msgbuf[256];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(msgbuf, 255, fmt, args);
+    va_end(args) ;
+#ifdef HAVE_GLIB
+    g_warning("SioxImage error: %s\n", msgbuf);
+#else
+    fprintf(stderr, "SioxImage error: %s\n", msgbuf);
+#endif
+}
+
+
+/**
+ * Returns true if the previous operation on this image
+ * was successful, else false.
+ */
+bool SioxImage::isValid()
+{
+    return valid;
+}
+
+/**
+ * Sets whether an operation was successful, and whether
+ * this image should be considered a valid one.
+ * was successful, else false.
+ */
+void SioxImage::setValid(bool val)
+{
+    valid = val;
+}
+
+
+/**
+ * Set a pixel at the x,y coordinates to the given value.
+ * If the coordinates are out of range, do nothing.
+ */
+void SioxImage::setPixel(unsigned int x,
+                         unsigned int y,
+                         unsigned int pixval)
+{
+    if (x >= width || y >= height)
+        {
+        error("setPixel: out of bounds (%d,%d)/(%d,%d)",
+                   x, y, width, height);
+        return;
+        }
+    unsigned long offset = width * y + x;
+    pixdata[offset] = pixval;
+}
+
+/**
+ * Set a pixel at the x,y coordinates to the given r, g, b values.
+ * If the coordinates are out of range, do nothing.
+ */
+void SioxImage::setPixel(unsigned int x, unsigned int y,
+                         unsigned int a,
+                         unsigned int r,
+                         unsigned int g,
+                         unsigned int b)
+{
+    if (x >= width || y >= height)
+        {
+        error("setPixel: out of bounds (%d,%d)/(%d,%d)",
+                   x, y, width, height);
+        return;
+        }
+    unsigned long offset = width * y + x;
+    unsigned int pixval = ((a << 24) & 0xff000000) |
+                          ((r << 16) & 0x00ff0000) |
+                          ((g <<  8) & 0x0000ff00) |
+                          ((b      ) & 0x000000ff);
+    pixdata[offset] = pixval;
+}
+
+
+
+/**
+ *  Get a pixel at the x,y coordinates given.  If
+ *  the coordinates are out of range, return 0;
+ */
+unsigned int SioxImage::getPixel(unsigned int x, unsigned int y)
+{
+    if (x >= width || y >= height)
+        {
+        error("getPixel: out of bounds (%d,%d)/(%d,%d)",
+                   x, y, width, height);
+        return 0L;
+        }
+    unsigned long offset = width * y + x;
+    return pixdata[offset];
+}
+
+/**
+ *  Return the image data buffer
+ */
+unsigned int *SioxImage::getImageData()
+{
+    return pixdata;
+}
+
+/**
+ * Set a confidence value at the x,y coordinates to the given value.
+ * If the coordinates are out of range, do nothing.
+ */
+void SioxImage::setConfidence(unsigned int x,
+                              unsigned int y,
+                              float confval)
+{
+    if (x >= width || y >= height)
+        {
+        error("setConfidence: out of bounds (%d,%d)/(%d,%d)",
+                   x, y, width, height);
+        return;
+        }
+    unsigned long offset = width * y + x;
+    cmdata[offset] = confval;
+}
+
+/**
+ *  Get a confidence valueat the x,y coordinates given.  If
+ *  the coordinates are out of range, return 0;
+ */
+float SioxImage::getConfidence(unsigned int x, unsigned int y)
+{
+    if (x >= width || y >= height)
+        {
+        error("getConfidence: out of bounds (%d,%d)/(%d,%d)",
+                   x, y, width, height);
+        return 0.0;
+        }
+    unsigned long offset = width * y + x;
+    return cmdata[offset];
+}
+
+/**
+ *  Return the confidence data buffer
+ */
+float *SioxImage::getConfidenceData()
+{
+    return cmdata;
+}
+
+
+/**
+ * Return the width of this image
+ */
+int SioxImage::getWidth()
+{
+    return width;
+}
+
+/**
+ * Return the height of this image
+ */
+int SioxImage::getHeight()
+{
+    return height;
+}
+
+/**
+ * Initialize values.  Used by constructors
+ */
+void SioxImage::init(unsigned int widthArg, unsigned int heightArg)
+{
+    valid     = true;
+    width     = widthArg;
+    height    = heightArg;
+    imageSize = width * height;
+    pixdata   = new unsigned int[imageSize];
+    cmdata    = new float[imageSize];
+    for (unsigned long i=0 ; i<imageSize ; i++)
+        {
+        pixdata[i] = 0;
+        cmdata[i]  = 0.0;
+        }
+}
+
+/**
+ * Assign values to that of another
+ */
+void SioxImage::assign(const SioxImage &other)
+{
+    if (pixdata) delete[] pixdata;
+    if (cmdata)  delete[] cmdata;
+    valid     = other.valid;
+    width     = other.width;
+    height    = other.height;
+    imageSize = width * height;
+    pixdata   = new unsigned int[imageSize];
+    cmdata    = new float[imageSize];
+    for (unsigned long i=0 ; i<imageSize ; i++)
+        {
+        pixdata[i] = other.pixdata[i];
+        cmdata[i]  = other.cmdata[i];
+        }
+}
+
+
+/**
+ * Write the image to a PPM file
+ */
+bool SioxImage::writePPM(const std::string &fileName)
+{
+
+    FILE *f = fopen(fileName.c_str(), "wb");
+    if (!f)
+        return false;
+
+    fprintf(f, "P6 %u %u 255\n", width, height);
+
+    for (unsigned int y=0 ; y<height; y++)
+        {
+        for (unsigned int x=0 ; x<width ; x++)
+            {
+            unsigned int rgb = getPixel(x, y);
+            //unsigned int alpha = (rgb>>24) & 0xff;
+            unsigned int r = ((rgb>>16) & 0xff);
+            unsigned int g = ((rgb>> 8) & 0xff);
+            unsigned int b = ((rgb    ) & 0xff);
+            fputc((unsigned char) r, f);
+            fputc((unsigned char) g, f);
+            fputc((unsigned char) b, f);
+            }
+        }
+    fclose(f);
+    return true;
+}
+
+
+#ifdef HAVE_GLIB
+
+/**
+ * Create an image from a GdkPixbuf
+ */
+SioxImage::SioxImage(GdkPixbuf *buf)
+{
+    if (!buf)
+        return;
+
+    unsigned int width  = gdk_pixbuf_get_width(buf);
+    unsigned int height = gdk_pixbuf_get_height(buf);
+    init(width, height); //DO THIS NOW!!
+
+
+    guchar *pixldata    = gdk_pixbuf_get_pixels(buf);
+    int rowstride       = gdk_pixbuf_get_rowstride(buf);
+    int n_channels      = gdk_pixbuf_get_n_channels(buf);
+
+    //### Fill in the cells with RGB values
+    int row  = 0;
+    for (unsigned int y=0 ; y<height ; y++)
+        {
+        guchar *p = pixldata + row;
+        for (unsigned int x=0 ; x<width ; x++)
+            {
+            int r     = (int)p[0];
+            int g     = (int)p[1];
+            int b     = (int)p[2];
+            int alpha = (int)p[3];
+
+            setPixel(x, y, alpha, r, g, b);
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+
+}
+
+
+/**
+ * Create a GdkPixbuf from this image
+ */
+GdkPixbuf *SioxImage::getGdkPixbuf()
+{
+    bool has_alpha = true;
+    int n_channels = has_alpha ? 4 : 3;
+
+    guchar *pixdata = (guchar *)
+          malloc(sizeof(guchar) * width * height * n_channels);
+    if (!pixdata)
+        {
+        error("SioxImage::getGdkPixbuf: can not allocate memory for %d x %d x %d image.", width, height, n_channels);
+        return nullptr;
+        }
+
+    int rowstride  = width * n_channels;
+
+    GdkPixbuf *buf = gdk_pixbuf_new_from_data(pixdata,
+                        GDK_COLORSPACE_RGB,
+                        has_alpha, 8, width, height,
+                        rowstride, (GdkPixbufDestroyNotify)free, nullptr);
+
+    //### Fill in the cells with RGB values
+    int row  = 0;
+    for (unsigned int y=0 ; y < height ; y++)
+        {
+        guchar *p = pixdata + row;
+        for (unsigned x=0 ; x < width ; x++)
+            {
+            unsigned int rgb = getPixel(x, y);
+            p[0] = (rgb >> 16) & 0xff;//r
+            p[1] = (rgb >>  8) & 0xff;//g
+            p[2] = (rgb      ) & 0xff;//b
+            if ( n_channels > 3 )
+                {
+                p[3] = (rgb >> 24) & 0xff;//a
+                }
+            p += n_channels;
+            }
+        row += rowstride;
+        }
+    return buf;
+}
+
+#endif /* GLIB */
+
+
+
+
+//########################################################################
+//#  S I O X
+//########################################################################
+
+//##############
+//## PUBLIC
+//##############
+
+/**
+ * Confidence corresponding to a certain foreground region (equals one).
+ */
+const float Siox::CERTAIN_FOREGROUND_CONFIDENCE=1.0f;
+
+/**
+ * Confidence for a region likely being foreground.
+ */
+const float Siox::FOREGROUND_CONFIDENCE=0.8f;
+
+/**
+ * Confidence for foreground or background type being equally likely.
+ */
+const float Siox::UNKNOWN_REGION_CONFIDENCE=0.5f;
+
+/**
+ * Confidence for a region likely being background.
+ */
+const float Siox::BACKGROUND_CONFIDENCE=0.1f;
+
+/**
+ * Confidence corresponding to a certain background reagion (equals zero).
+ */
+const float Siox::CERTAIN_BACKGROUND_CONFIDENCE=0.0f;
+
+/**
+ *  Construct a Siox engine
+ */
+Siox::Siox() :
+    sioxObserver(nullptr),
+    keepGoing(true),
+    width(0),
+    height(0),
+    pixelCount(0),
+    image(nullptr),
+    cm(nullptr),
+    labelField(nullptr)
+{
+    init();
+}
+
+/**
+ *  Construct a Siox engine
+ */
+Siox::Siox(SioxObserver *observer) :
+    sioxObserver(observer),
+    keepGoing(true),
+    width(0),
+    height(0),
+    pixelCount(0),
+    image(nullptr),
+    cm(nullptr),
+    labelField(nullptr)
+{
+    init();
+}
+
+
+/**
+ *
+ */
+Siox::~Siox()
+{
+    cleanup();
+}
+
+
+/**
+ * Error logging
+ */
+void Siox::error(const char *fmt, ...)
+{
+    char msgbuf[256];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(msgbuf, 255, fmt, args);
+    va_end(args) ;
+#ifdef HAVE_GLIB
+    g_warning("Siox error: %s\n", msgbuf);
+#else
+    fprintf(stderr, "Siox error: %s\n", msgbuf);
+#endif
+}
+
+/**
+ * Trace logging
+ */
+void Siox::trace(const char *fmt, ...)
+{
+    char msgbuf[256];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(msgbuf, 255, fmt, args);
+    va_end(args) ;
+#ifdef HAVE_GLIB
+    g_message("Siox: %s\n", msgbuf);
+#else
+    fprintf(stdout, "Siox: %s\n", msgbuf);
+#endif
+}
+
+
+
+/**
+ * Progress reporting
+ */
+bool Siox::progressReport(float percentCompleted)
+{
+    if (!sioxObserver)
+        return true;
+
+    bool ret = sioxObserver->progress(percentCompleted);
+
+    if (!ret)
+      {
+      trace("User selected abort");
+      keepGoing = false;
+      }
+
+    return ret;
+}
+
+
+
+
+/**
+ *  Extract the foreground of the original image, according
+ *  to the values in the confidence matrix.
+ */
+SioxImage Siox::extractForeground(const SioxImage &originalImage,
+                                  unsigned int backgroundFillColor)
+{
+    trace("### Start");
+
+    init();
+    keepGoing = true;
+
+    SioxImage workImage = originalImage;
+
+    //# fetch some info from the image
+    width      = workImage.getWidth();
+    height     = workImage.getHeight();
+    pixelCount = width * height;
+    image      = workImage.getImageData();
+    cm         = workImage.getConfidenceData();
+    labelField = new int[pixelCount];
+
+    trace("### Creating signatures");
+
+    //#### create color signatures
+    std::vector<CieLab> knownBg;
+    std::vector<CieLab> knownFg;
+    CieLab *imageClab = new CieLab[pixelCount];
+    for (unsigned long i=0 ; i<pixelCount ; i++)
+        {
+        float conf = cm[i];
+        unsigned int pix = image[i];
+        CieLab lab(pix);
+        imageClab[i] = lab;
+        if (conf <= BACKGROUND_CONFIDENCE)
+            knownBg.push_back(lab);
+        else if (conf >= FOREGROUND_CONFIDENCE)
+            knownFg.push_back(lab);
+        }
+
+    /*
+    std::vector<CieLab> imageClab;
+    for (int y = 0 ; y < workImage.getHeight() ; y++)
+        for (int x = 0 ; x < workImage.getWidth() ; x++)
+            {
+            float cm = workImage.getConfidence(x, y);
+            unsigned int pix = workImage.getPixel(x, y);
+            CieLab lab(pix);
+            imageClab.push_back(lab);
+            if (cm <= BACKGROUND_CONFIDENCE)
+                knownBg.push_back(lab); //note: uses CieLab(rgb)
+            else if (cm >= FOREGROUND_CONFIDENCE)
+                knownFg.push_back(lab);
+            }
+    */
+
+    if (!progressReport(10.0))
+        {
+        error("User aborted");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+    trace("knownBg:%u knownFg:%u", static_cast<unsigned int>(knownBg.size()), static_cast<unsigned int>(knownFg.size()));
+
+
+    std::vector<CieLab> bgSignature ;
+    if (!colorSignature(knownBg, bgSignature, 3))
+        {
+        error("Could not create background signature");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+    if (!progressReport(30.0))
+        {
+        error("User aborted");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+
+    std::vector<CieLab> fgSignature ;
+    if (!colorSignature(knownFg, fgSignature, 3))
+        {
+        error("Could not create foreground signature");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+    //trace("### bgSignature:%d", bgSignature.size());
+
+    if (bgSignature.empty())
+        {
+        // segmentation impossible
+        error("Signature size is < 1.  Segmentation is impossible");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+    if (!progressReport(30.0))
+        {
+        error("User aborted");
+        workImage.setValid(false);
+        delete[] imageClab;
+        delete[] labelField;
+        return workImage;
+        }
+
+
+    // classify using color signatures,
+    // classification cached in hashmap for drb and speedup purposes
+    trace("### Analyzing image");
+
+    std::map<unsigned int, Tupel> hs;
+
+    unsigned int progressResolution = pixelCount / 10;
+
+    for (unsigned int i=0; i<pixelCount; i++)
+        {
+        if (i % progressResolution == 0)
+            {
+            float progress =
+                30.0 + 60.0 * (float)i / (float)pixelCount;
+            //trace("### progress:%f", progress);
+            if (!progressReport(progress))
+                {
+                error("User aborted");
+                delete[] imageClab;
+                delete[] labelField;
+                workImage.setValid(false);
+                return workImage;
+                }
+            }
+
+        if (cm[i] >= FOREGROUND_CONFIDENCE)
+            {
+            cm[i] = CERTAIN_FOREGROUND_CONFIDENCE;
+            }
+        else if (cm[i] <= BACKGROUND_CONFIDENCE)
+            {
+            cm[i] = CERTAIN_BACKGROUND_CONFIDENCE;
+            }
+        else // somewhere in between
+            {
+            bool isBackground = true;
+            std::map<unsigned int, Tupel>::iterator iter = hs.find(i);
+            if (iter != hs.end()) //found
+                {
+                Tupel tupel  = iter->second;
+                isBackground = tupel.minBgDist <= tupel.minFgDist;
+                }
+            else
+                {
+                CieLab lab   = imageClab[i];
+                float minBg  = lab.diffSq(bgSignature[0]);
+                int minIndex = 0;
+                for (unsigned int j=1; j<bgSignature.size() ; j++)
+                    {
+                    float d = lab.diffSq(bgSignature[j]);
+                    if (d<minBg)
+                        {
+                        minBg    = d;
+                        minIndex = j;
+                        }
+                    }
+                Tupel tupel(0.0f, 0,  0.0f, 0);
+                tupel.minBgDist  = minBg;
+                tupel.indexMinBg = minIndex;
+                float minFg      = 1.0e6f;
+                minIndex         = -1;
+                for (unsigned int j = 0 ; j < fgSignature.size() ; j++)
+                    {
+                    float d = lab.diffSq(fgSignature[j]);
+                    if (d < minFg)
+                        {
+                        minFg    = d;
+                        minIndex = j;
+                        }
+                    }
+                tupel.minFgDist  = minFg;
+                tupel.indexMinFg = minIndex;
+                if (fgSignature.empty())
+                    {
+                    isBackground = (minBg <= clusterSize);
+                    // remove next line to force behaviour of old algorithm
+                    //error("foreground signature does not exist");
+                    //delete[] labelField;
+                    //workImage.setValid(false);
+                    //return workImage;
+                    }
+                else
+                    {
+                    isBackground = minBg < minFg;
+                    }
+                hs[image[i]] = tupel;
+                }
+
+            if (isBackground)
+                cm[i] = CERTAIN_BACKGROUND_CONFIDENCE;
+            else
+                cm[i] = CERTAIN_FOREGROUND_CONFIDENCE;
+            }
+        }
+
+
+    delete[] imageClab;
+
+    trace("### postProcessing");
+
+
+    //#### postprocessing
+    smooth(cm, width, height, 0.333f, 0.333f, 0.333f); // average
+    normalizeMatrix(cm, pixelCount);
+    erode(cm, width, height);
+    keepOnlyLargeComponents(UNKNOWN_REGION_CONFIDENCE, 1.0/*sizeFactorToKeep*/);
+
+    //for (int i=0; i < 2/*smoothness*/; i++)
+    //    smooth(cm, width, height, 0.333f, 0.333f, 0.333f); // average
+
+    normalizeMatrix(cm, pixelCount);
+
+    for (unsigned int i=0; i < pixelCount; i++)
+        {
+        if (cm[i] >= UNKNOWN_REGION_CONFIDENCE)
+            cm[i] = CERTAIN_FOREGROUND_CONFIDENCE;
+        else
+            cm[i] = CERTAIN_BACKGROUND_CONFIDENCE;
+        }
+
+    keepOnlyLargeComponents(UNKNOWN_REGION_CONFIDENCE, 1.5/*sizeFactorToKeep*/);
+    fillColorRegions();
+    dilate(cm, width, height);
+
+    if (!progressReport(100.0))
+        {
+        error("User aborted");
+        delete[] labelField;
+        workImage.setValid(false);
+        return workImage;
+        }
+
+
+    //#### We are done.  Now clear everything but the background
+    for (unsigned long i = 0; i<pixelCount ; i++)
+        {
+        float conf = cm[i];
+        if (conf < FOREGROUND_CONFIDENCE)
+            image[i] = backgroundFillColor;
+        }
+
+    delete[] labelField;
+
+    trace("### Done");
+    keepGoing = false;
+    return workImage;
+}
+
+
+
+//##############
+//## PRIVATE
+//##############
+
+/**
+ *  Initialize the Siox engine to its 'pristine' state.
+ *  Performed at the beginning of extractForeground().
+ */
+void Siox::init()
+{
+    limits[0] = 0.64f;
+    limits[1] = 1.28f;
+    limits[2] = 2.56f;
+
+    float negLimits[3];
+    negLimits[0] = -limits[0];
+    negLimits[1] = -limits[1];
+    negLimits[2] = -limits[2];
+
+    clusterSize = sqrEuclideanDist(limits, 3, negLimits);
+}
+
+
+/**
+ *  Clean up any debris from processing.
+ */
+void Siox::cleanup()
+{
+}
+
+
+
+
+/**
+ *  Stage 1 of the color signature work.  'dims' will be either
+ *  2 for grays, or 3 for colors
+ */
+void Siox::colorSignatureStage1(CieLab *points,
+                                unsigned int leftBase,
+                                unsigned int rightBase,
+                                unsigned int recursionDepth,
+                                unsigned int *clusterCount,
+                                const unsigned int dims)
+{
+
+    unsigned int currentDim = recursionDepth % dims;
+    CieLab point = points[leftBase];
+    float min = point(currentDim);
+    float max = min;
+
+    for (unsigned int i = leftBase + 1; i < rightBase ; i++)
+        {
+        point = points[i];
+        float curval = point(currentDim);
+        if (curval < min) min = curval;
+        if (curval > max) max = curval;
+        }
+
+    //Do the Rubner-rule split (sounds like a dance)
+    if (max - min > limits[currentDim])
+        {
+        float pivotPoint = (min + max) / 2.0; //average
+        unsigned int left  = leftBase;
+        unsigned int right = rightBase - 1;
+
+        //# partition points according to the dimension
+        while (true)
+            {
+            while ( true )
+                {
+                point = points[left];
+                if (point(currentDim) > pivotPoint)
+                    break;
+                left++;
+                }
+            while ( true )
+                {
+                point = points[right];
+                if (point(currentDim) <= pivotPoint)
+                    break;
+                right--;
+                }
+
+            if (left > right)
+                break;
+
+            point = points[left];
+            points[left] = points[right];
+            points[right] = point;
+
+            left++;
+            right--;
+            }
+
+        //# Recurse and create sub-trees
+        colorSignatureStage1(points, leftBase, left,
+                 recursionDepth + 1, clusterCount, dims);
+        colorSignatureStage1(points, left, rightBase,
+                 recursionDepth + 1, clusterCount, dims);
+        }
+    else
+        {
+        //create a leaf
+        CieLab newpoint;
+
+        newpoint.C = rightBase - leftBase;
+
+        for (; leftBase < rightBase ; leftBase++)
+            {
+            newpoint.add(points[leftBase]);
+            }
+
+        //printf("clusters:%d\n", *clusters);
+
+        if (newpoint.C != 0)
+            newpoint.mul(1.0 / (float)newpoint.C);
+        points[*clusterCount] = newpoint;
+        (*clusterCount)++;
+        }
+}
+
+
+
+/**
+ *  Stage 2 of the color signature work
+ */
+void Siox::colorSignatureStage2(CieLab         *points,
+                                unsigned int leftBase,
+                                unsigned int rightBase,
+                                unsigned int recursionDepth,
+                                unsigned int *clusterCount,
+                                const float  threshold,
+                                const unsigned int dims)
+{
+    unsigned int currentDim = recursionDepth % dims;
+    CieLab point = points[leftBase];
+    float min = point(currentDim);
+    float max = min;
+
+    for (unsigned int i = leftBase+ 1; i < rightBase; i++)
+        {
+        point = points[i];
+        float curval = point(currentDim);
+        if (curval < min) min = curval;
+        if (curval > max) max = curval;
+        }
+
+    //Do the Rubner-rule split (sounds like a dance)
+    if (max - min > limits[currentDim])
+        {
+        float pivotPoint = (min + max) / 2.0; //average
+        unsigned int left  = leftBase;
+        unsigned int right = rightBase - 1;
+
+        //# partition points according to the dimension
+        while (true)
+            {
+            while ( true )
+                {
+                point = points[left];
+                if (point(currentDim) > pivotPoint)
+                    break;
+                left++;
+                }
+            while ( true )
+                {
+                point = points[right];
+                if (point(currentDim) <= pivotPoint)
+                    break;
+                right--;
+                }
+
+            if (left > right)
+                break;
+
+            point = points[left];
+            points[left] = points[right];
+            points[right] = point;
+
+            left++;
+            right--;
+            }
+
+        //# Recurse and create sub-trees
+        colorSignatureStage2(points, leftBase, left,
+                 recursionDepth + 1, clusterCount, threshold, dims);
+        colorSignatureStage2(points, left, rightBase,
+                 recursionDepth + 1, clusterCount, threshold, dims);
+        }
+    else
+        {
+        //### Create a leaf
+        unsigned int sum = 0;
+        for (unsigned int i = leftBase; i < rightBase; i++)
+            sum += points[i].C;
+
+        if ((float)sum >= threshold)
+            {
+            float scale = (float)(rightBase - leftBase);
+            CieLab newpoint;
+
+            for (; leftBase < rightBase; leftBase++)
+                newpoint.add(points[leftBase]);
+
+            if (scale != 0.0)
+                newpoint.mul(1.0 / scale);
+            points[*clusterCount] = newpoint;
+            (*clusterCount)++;
+            }
+      }
+}
+
+
+
+/**
+ *  Main color signature method
+ */
+bool Siox::colorSignature(const std::vector<CieLab> &inputVec,
+                          std::vector<CieLab> &result,
+                          const unsigned int dims)
+{
+
+    unsigned int length = inputVec.size();
+
+    if (length < 1) // no error. just don't do anything
+        return true;
+
+    CieLab *input = new CieLab [length];
+
+    if (!input)
+    {
+        error("Could not allocate buffer for signature");
+        return false;
+    }
+    for (unsigned int i=0 ; i < length ; i++)
+    {
+        input[i] = inputVec[i];
+    }
+
+    unsigned int stage1length = 0;
+    colorSignatureStage1(input, 0, length, 0, &stage1length, dims);
+
+    unsigned int stage2length = 0;
+    colorSignatureStage2(input, 0, stage1length, 0, &stage2length, length * 0.001, dims);
+
+    result.clear();
+    for (unsigned int i=0 ; i < stage2length ; i++)
+    {
+        result.push_back(input[i]);
+    }
+
+    delete[] input;
+
+    return true;
+}
+
+
+
+/**
+ *
+ */
+void Siox::keepOnlyLargeComponents(float threshold,
+                                   double sizeFactorToKeep)
+{
+    for (unsigned long idx = 0 ; idx<pixelCount ; idx++)
+        labelField[idx] = -1;
+
+    int curlabel = 0;
+    int maxregion= 0;
+    int maxblob  = 0;
+
+    // slow but easy to understand:
+    std::vector<int> labelSizes;
+    for (unsigned long i=0 ; i<pixelCount ; i++)
+        {
+        int regionCount = 0;
+        if (labelField[i] == -1 && cm[i] >= threshold)
+            {
+            regionCount = depthFirstSearch(i, threshold, curlabel++);
+            labelSizes.push_back(regionCount);
+            }
+
+        if (regionCount>maxregion)
+            {
+            maxregion = regionCount;
+            maxblob   = curlabel-1;
+            }
+        }
+
+    for (unsigned int i=0 ; i<pixelCount ; i++)
+        {
+        if (labelField[i] != -1)
+            {
+            // remove if the component is to small
+            if (labelSizes[labelField[i]] * sizeFactorToKeep < maxregion)
+                cm[i] = CERTAIN_BACKGROUND_CONFIDENCE;
+
+            // add maxblob always to foreground
+            if (labelField[i] == maxblob)
+                cm[i] = CERTAIN_FOREGROUND_CONFIDENCE;
+            }
+        }
+
+}
+
+
+
+int Siox::depthFirstSearch(int startPos,
+              float threshold, int curLabel)
+{
+    // stores positions of labeled pixels, where the neighbours
+    // should still be checked for processing:
+
+    //trace("startPos:%d threshold:%f curLabel:%d",
+    //     startPos, threshold, curLabel);
+
+    std::vector<int> pixelsToVisit;
+    int componentSize = 0;
+
+    if (labelField[startPos]==-1 && cm[startPos]>=threshold)
+        {
+        labelField[startPos] = curLabel;
+        componentSize++;
+        pixelsToVisit.push_back(startPos);
+        }
+
+
+    while (!pixelsToVisit.empty())
+        {
+        int pos = pixelsToVisit[pixelsToVisit.size() - 1];
+        pixelsToVisit.erase(pixelsToVisit.end() - 1);
+        unsigned int x = pos % width;
+        unsigned int y = pos / width;
+
+        // check all four neighbours
+        int left = pos - 1;
+        if (((int)x)-1>=0 && labelField[left]==-1 && cm[left]>=threshold)
+            {
+            labelField[left]=curLabel;
+            componentSize++;
+            pixelsToVisit.push_back(left);
+            }
+
+        int right = pos + 1;
+        if (x+1 < width && labelField[right]==-1 && cm[right]>=threshold)
+            {
+            labelField[right]=curLabel;
+            componentSize++;
+            pixelsToVisit.push_back(right);
+            }
+
+        int top = pos - width;
+        if (((int)y)-1>=0 && labelField[top]==-1 && cm[top]>=threshold)
+            {
+            labelField[top]=curLabel;
+            componentSize++;
+            pixelsToVisit.push_back(top);
+            }
+
+        int bottom = pos + width;
+        if (y+1 < height && labelField[bottom]==-1
+                         && cm[bottom]>=threshold)
+            {
+            labelField[bottom]=curLabel;
+            componentSize++;
+            pixelsToVisit.push_back(bottom);
+            }
+
+        }
+    return componentSize;
+}
+
+
+
+/**
+ *
+ */
+void Siox::fillColorRegions()
+{
+    for (unsigned long idx = 0 ; idx<pixelCount ; idx++)
+        labelField[idx] = -1;
+
+    //int maxRegion=0; // unused now
+    std::vector<int> pixelsToVisit;
+    for (unsigned long i=0; i<pixelCount; i++)
+        { // for all pixels
+        if (labelField[i]!=-1 || cm[i]<UNKNOWN_REGION_CONFIDENCE)
+            {
+            continue; // already visited or bg
+            }
+
+        unsigned int  origColor = image[i];
+        unsigned long curLabel  = i+1;
+        labelField[i]           = curLabel;
+        cm[i]                   = CERTAIN_FOREGROUND_CONFIDENCE;
+
+        // int componentSize = 1;
+        pixelsToVisit.push_back(i);
+        // depth first search to fill region
+        while (!pixelsToVisit.empty())
+            {
+            int pos = pixelsToVisit[pixelsToVisit.size() - 1];
+            pixelsToVisit.erase(pixelsToVisit.end() - 1);
+            unsigned int x=pos % width;
+            unsigned int y=pos / width;
+            // check all four neighbours
+            int left = pos-1;
+            if (((int)x)-1 >= 0 && labelField[left] == -1
+                        && CieLab::diff(image[left], origColor)<1.0)
+                {
+                labelField[left]=curLabel;
+                cm[left]=CERTAIN_FOREGROUND_CONFIDENCE;
+                // ++componentSize;
+                pixelsToVisit.push_back(left);
+                }
+            int right = pos+1;
+            if (x+1 < width && labelField[right]==-1
+                        && CieLab::diff(image[right], origColor)<1.0)
+                {
+                labelField[right]=curLabel;
+                cm[right]=CERTAIN_FOREGROUND_CONFIDENCE;
+                // ++componentSize;
+                pixelsToVisit.push_back(right);
+                }
+            int top = pos - width;
+            if (((int)y)-1>=0 && labelField[top]==-1
+                        && CieLab::diff(image[top], origColor)<1.0)
+                {
+                labelField[top]=curLabel;
+                cm[top]=CERTAIN_FOREGROUND_CONFIDENCE;
+                // ++componentSize;
+                pixelsToVisit.push_back(top);
+                }
+            int bottom = pos + width;
+            if (y+1 < height && labelField[bottom]==-1
+                        && CieLab::diff(image[bottom], origColor)<1.0)
+                {
+                labelField[bottom]=curLabel;
+                cm[bottom]=CERTAIN_FOREGROUND_CONFIDENCE;
+                // ++componentSize;
+                pixelsToVisit.push_back(bottom);
+                }
+            }
+        //if (componentSize>maxRegion) {
+        //    maxRegion=componentSize;
+        //}
+        }
+}
+
+
+
+
+/**
+ * Applies the morphological dilate operator.
+ *
+ * Can be used to close small holes in the given confidence matrix.
+ */
+void Siox::dilate(float *cm, int xres, int yres)
+{
+
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=0; x<xres-1; x++)
+             {
+             int idx=(y*xres)+x;
+             if (cm[idx+1]>cm[idx])
+                 cm[idx]=cm[idx+1];
+             }
+        }
+
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=xres-1; x>=1; x--)
+            {
+            int idx=(y*xres)+x;
+            if (cm[idx-1]>cm[idx])
+                cm[idx]=cm[idx-1];
+            }
+        }
+
+    for (int y=0; y<yres-1; y++)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            if (cm[((y+1)*xres)+x] > cm[idx])
+                cm[idx]=cm[((y+1)*xres)+x];
+            }
+        }
+
+    for (int y=yres-1; y>=1; y--)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            if (cm[((y-1)*xres)+x] > cm[idx])
+                cm[idx]=cm[((y-1)*xres)+x];
+            }
+        }
+}
+
+/**
+ * Applies the morphological erode operator.
+ */
+void Siox::erode(float *cm, int xres, int yres)
+{
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=0; x<xres-1; x++)
+            {
+            int idx=(y*xres)+x;
+            if (cm[idx+1] < cm[idx])
+                cm[idx]=cm[idx+1];
+            }
+        }
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=xres-1; x>=1; x--)
+            {
+            int idx=(y*xres)+x;
+            if (cm[idx-1] < cm[idx])
+                cm[idx]=cm[idx-1];
+            }
+        }
+    for (int y=0; y<yres-1; y++)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            if (cm[((y+1)*xres)+x] < cm[idx])
+                cm[idx]=cm[((y+1)*xres)+x];
+            }
+        }
+    for (int y=yres-1; y>=1; y--)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            if (cm[((y-1)*xres)+x] < cm[idx])
+                cm[idx]=cm[((y-1)*xres)+x];
+            }
+        }
+}
+
+
+
+/**
+ * Normalizes the matrix to values to [0..1].
+ */
+void Siox::normalizeMatrix(float *cm, int cmSize)
+{
+    float max= -1000000.0f;
+    for (int i=0; i<cmSize; i++)
+        if (cm[i] > max) max=cm[i];
+
+    //good to use STL, but max() is not iterative
+    //float max = *std::max(cm, cm + cmSize);
+
+    if (max<=0.0 || max==1.0)
+        return;
+
+    float alpha=1.00f/max;
+    premultiplyMatrix(alpha, cm, cmSize);
+}
+
+/**
+ * Multiplies matrix with the given scalar.
+ */
+void Siox::premultiplyMatrix(float alpha, float *cm, int cmSize)
+{
+    for (int i=0; i<cmSize; i++)
+        cm[i]=alpha*cm[i];
+}
+
+/**
+ * Blurs confidence matrix with a given symmetrically weighted kernel.
+ *
+ * In the standard case confidence matrix entries are between 0...1 and
+ * the weight factors sum up to 1.
+ */
+void Siox::smooth(float *cm, int xres, int yres,
+                  float f1, float f2, float f3)
+{
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=0; x<xres-2; x++)
+            {
+            int idx=(y*xres)+x;
+            cm[idx]=f1*cm[idx]+f2*cm[idx+1]+f3*cm[idx+2];
+            }
+        }
+    for (int y=0; y<yres; y++)
+        {
+        for (int x=xres-1; x>=2; x--)
+            {
+            int idx=(y*xres)+x;
+            cm[idx]=f3*cm[idx-2]+f2*cm[idx-1]+f1*cm[idx];
+            }
+        }
+    for (int y=0; y<yres-2; y++)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            cm[idx]=f1*cm[idx]+f2*cm[((y+1)*xres)+x]+f3*cm[((y+2)*xres)+x];
+            }
+        }
+    for (int y=yres-1; y>=2; y--)
+        {
+        for (int x=0; x<xres; x++)
+            {
+            int idx=(y*xres)+x;
+            cm[idx]=f3*cm[((y-2)*xres)+x]+f2*cm[((y-1)*xres)+x]+f1*cm[idx];
+            }
+        }
+}
+
+/**
+ * Squared Euclidean distance of p and q.
+ */
+float Siox::sqrEuclideanDist(float *p, int pSize, float *q)
+{
+    float sum=0.0;
+    for (int i=0; i<pSize; i++)
+        {
+        float v = p[i] - q[i];
+        sum += v*v;
+        }
+    return sum;
+}
+
+
+
+
+
+
+} // namespace siox
+} // namespace org
+
+//########################################################################
+//#  E N D    O F    F I L E
+//########################################################################
+
diff --git a/src/trace/siox.h b/src/trace/siox.h
new file mode 100644
index 0000000..10eb62b
--- /dev/null
+++ b/src/trace/siox.h
@@ -0,0 +1,654 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_SIOX_H
+#define SEEN_SIOX_H
+/*
+ *  Copyright 2005, 2006 by Gerald Friedland, Kristian Jantz and Lars Knipping
+ *
+ *  Conversion to C++ for Inkscape by Bob Jamison
+ *
+ *  Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+/*
+ * Note by Bob Jamison:
+ * After translating the siox.org Java API to C++ and receiving an
+ * education into this wonderful code,  I began again,
+ * and started this version using lessons learned.  This version is
+ * an attempt to provide an dependency-free SIOX engine that anyone
+ * can use in their project with minimal effort.
+ *
+ * Many thanks to the fine people at siox.org.
+ */
+
+#include <string>
+#include <vector>
+
+#define HAVE_GLIB
+
+#ifdef HAVE_GLIB
+#include <glib.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+#endif
+
+
+namespace org
+{
+
+namespace siox
+{
+
+
+//########################################################################
+//#  C L A B
+//########################################################################
+
+/**
+ *
+ */
+class CieLab
+{
+public:
+
+    /**
+     *
+     */
+    CieLab()
+        {
+        init();
+        C = 0;
+        L = A = B = 0.0f;
+        }
+
+
+    /**
+     *
+     */
+    CieLab(unsigned long rgb);
+
+
+    /**
+     *
+     */
+    CieLab(float lArg, float aArg, float bArg)
+        {
+        init();
+        C = 0;
+        L = lArg;
+        A = aArg;
+        B = bArg;
+        }
+
+
+    /**
+     *
+     */
+    CieLab(const CieLab &other)
+        {
+        init();
+        C = other.C;
+        L = other.L;
+        A = other.A;
+        B = other.B;
+        }
+
+
+    /**
+     *
+     */
+    CieLab &operator=(const CieLab &other)
+        {
+        init();
+        C = other.C;
+        L = other.L;
+        A = other.A;
+        B = other.B;
+        return *this;
+        }
+
+    /**
+     *
+     */
+    virtual ~CieLab()
+        = default;
+
+    /**
+     * Retrieve a CieLab value via index.
+     */
+    virtual float operator()(unsigned int index)
+        {
+        if      (index==0) return L;
+        else if (index==1) return A;
+        else if (index==2) return B;
+        else return 0;
+        }
+
+
+    /**
+     *
+     */
+    virtual void add(const CieLab &other)
+        {
+        C += other.C;
+        L += other.L;
+        A += other.A;
+        B += other.B;
+        }
+
+
+    /**
+     *
+     */
+    virtual void mul(float scale)
+        {
+        L *= scale;
+        A *= scale;
+        B *= scale;
+        }
+
+
+    /**
+     *
+     */
+    virtual unsigned long toRGB();
+
+    /**
+     * Approximate cube roots
+     */
+    double cbrt(double x);
+
+    /**
+     *
+     */
+    double qnrt(double x);
+
+    /**
+     * Raise to the 2.4 power
+     */
+    double pow24(double x);
+
+    /**
+     * Squared Euclidean distance between this and another color
+     */
+    float diffSq(const CieLab &other);
+
+    /**
+     * Computes squared euclidean distance in CieLab space for two colors
+     * given as RGB values.
+     */
+    static float diffSq(unsigned int rgb1, unsigned int rgb2);
+
+    /**
+     * Computes squared euclidean distance in CieLab space for two colors
+     * given as RGB values.
+     */
+    static float diff(unsigned int rgb0, unsigned int rgb1);
+
+
+    unsigned int C;
+    float L;
+    float A;
+    float B;
+
+private:
+
+    /**
+     *
+     */
+    void init();
+
+
+};
+
+
+//########################################################################
+//#  S I O X    I M A G E
+//########################################################################
+
+/**
+ * This is a generic image type that provides a consistent interface
+ * to Siox, so that developers will not need to worry about data arrays.
+ */
+class SioxImage
+{
+public:
+
+    /**
+     *  Create an image with the given width and height
+     */
+    SioxImage(unsigned int width, unsigned int height);
+
+    /**
+     *  Copy constructor
+     */
+    SioxImage(const SioxImage &other);
+
+    /**
+     *  Assignment
+     */
+    SioxImage &operator=(const SioxImage &other);
+
+    /**
+     * Clean up after use.
+     */
+    virtual ~SioxImage();
+
+    /**
+     * Returns true if the previous operation on this image
+     * was successful, else false.
+     */
+    virtual bool isValid();
+
+    /**
+     * Sets whether an operation was successful, and whether
+     * this image should be considered a valid one.
+     * was successful, else false.
+     */
+    virtual void setValid(bool val);
+
+    /**
+     * Set a pixel at the x,y coordinates to the given value.
+     * If the coordinates are out of range, do nothing.
+     */
+    virtual void setPixel(unsigned int x,
+                          unsigned int y,
+                          unsigned int pixval);
+
+    /**
+     * Set a pixel at the x,y coordinates to the given r, g, b values.
+     * If the coordinates are out of range, do nothing.
+     */
+    virtual void setPixel(unsigned int x, unsigned int y,
+                          unsigned int a,
+                          unsigned int r,
+                          unsigned int g,
+                          unsigned int b);
+
+    /**
+     *  Get a pixel at the x,y coordinates given.  If
+     *  the coordinates are out of range, return 0
+     */
+    virtual unsigned int getPixel(unsigned int x, unsigned int y);
+
+
+    /**
+     *  Return the image data buffer
+     */
+    virtual unsigned int *getImageData();
+
+    /**
+     * Set a confidence value at the x,y coordinates to the given value.
+     * If the coordinates are out of range, do nothing.
+     */
+    virtual void setConfidence(unsigned int x,
+                               unsigned int y,
+                               float conf);
+
+    /**
+     *  Get a confidence value at the x,y coordinates given.  If
+     *  the coordinates are out of range, return 0
+     */
+    virtual float getConfidence(unsigned int x, unsigned int y);
+
+    /**
+     *  Return the confidence data buffer
+     */
+    virtual float *getConfidenceData();
+
+    /**
+     * Return the width of this image
+     */
+    virtual int getWidth();
+
+    /**
+     * Return the height of this image
+     */
+    virtual int getHeight();
+
+    /**
+     * Saves this image as a simple color PPM
+     */
+    bool writePPM(const std::string &fileName);
+
+
+
+#ifdef HAVE_GLIB
+
+    /**
+     * Special constructor to create an image from a GdkPixbuf.
+     */
+    SioxImage(GdkPixbuf *buf);
+
+    /**
+     * Creates a GdkPixbuf from this image.  The user must
+     * remember to destroy the image when no longer needed.
+     * with g_free(pixbuf)
+     */
+    GdkPixbuf *getGdkPixbuf();
+
+#endif
+
+private:
+
+    SioxImage()
+        = default;
+
+    /**
+     * Assign values to that of another
+     */
+    void assign(const SioxImage &other);
+
+    /**
+     * Initialize values.  Used by constructors
+     */
+    void init(unsigned int width, unsigned int height);
+
+    bool valid;
+
+    unsigned int width;
+
+    unsigned int height;
+
+    unsigned long imageSize;
+
+    /**
+     * Pixel data
+     */
+    unsigned int *pixdata;
+
+    /**
+     * Confidence matrix data
+     */
+    float *cmdata;
+
+private:
+
+    /**
+     * Error logging
+     */
+    void error(const char *fmt, ...) G_GNUC_PRINTF(2,3);
+
+};
+
+
+
+//########################################################################
+//#  S I O X    O B S E R V E R
+//########################################################################
+class Siox;
+
+/**
+ *  This is a class for observing the progress of a Siox engine.  Overload
+ *  the methods in your subclass to get the desired behaviour.
+ */
+class SioxObserver
+{
+public:
+
+    /**
+     *  Constructor.  Context can point to anything, and is usually
+     *  used to point to a C++ object or C state object, to delegate
+     *  callback processing to something else.  Use NULL to ignore.
+     */
+    SioxObserver(void *contextArg) : context(nullptr)
+        { context = contextArg; }
+
+    /**
+     *  Destructor
+     */
+    virtual ~SioxObserver()
+        = default;
+
+    /**
+     *  Informs the observer how much has been completed.
+     *  Return false if the processing should be aborted.
+     */
+    virtual bool progress(float /*percentCompleted*/)
+        {
+        return true;
+        }
+
+    /**
+     *  Send an error string to the Observer.  Processing will
+     *  be halted.
+     */
+    virtual void error(const std::string &/*msg*/)
+        {
+        }
+
+protected:
+
+    void *context;
+
+};
+
+
+
+//########################################################################
+//#  S I O X
+//########################################################################
+
+/**
+ *
+ */
+class Siox
+{
+public:
+
+    /**
+     * Confidence corresponding to a certain foreground region (equals one).
+     */
+    static const float CERTAIN_FOREGROUND_CONFIDENCE; //=1.0f;
+
+    /**
+     * Confidence for a region likely being foreground.
+     */
+    static const float FOREGROUND_CONFIDENCE; //=0.8f;
+
+    /**
+     * Confidence for foreground or background type being equally likely.
+     */
+    static const float UNKNOWN_REGION_CONFIDENCE; //=0.5f;
+
+    /**
+     * Confidence for a region likely being background.
+     */
+    static const float BACKGROUND_CONFIDENCE; //=0.1f;
+
+    /**
+     * Confidence corresponding to a certain background reagion (equals zero).
+     */
+    static const float CERTAIN_BACKGROUND_CONFIDENCE; //=0.0f;
+
+    /**
+     *  Construct a Siox engine
+     */
+    Siox();
+
+    /**
+     *  Construct a Siox engine.  Use null to ignore
+     */
+    Siox(SioxObserver *observer);
+
+    /**
+     *
+     */
+    virtual ~Siox();
+
+    /**
+     *  Extract the foreground of the original image, according
+     *  to the values in the confidence matrix.  If the operation fails,
+     *  sioxImage.isValid()  will be false.
+     *  backgroundFillColor is any ARGB color,  such as 0xffffff (white)
+     *  or 0x000000 (black)
+     */
+    virtual SioxImage extractForeground(const SioxImage &originalImage,
+                                        unsigned int backgroundFillColor);
+
+private:
+
+    SioxObserver *sioxObserver;
+
+    /**
+     * Progress reporting
+     */
+    bool progressReport(float percentCompleted);
+
+    /**
+     * Flag this as false during processing to abort
+     */
+    bool keepGoing;
+
+    /**
+     * Image width
+     */
+    unsigned int width;
+
+    /**
+     * Image height
+     */
+    unsigned int height;
+
+    /**
+     * Image size in pixels
+     */
+    unsigned long pixelCount;
+
+    /**
+     * Image data
+     */
+    unsigned int *image;
+
+    /**
+     * Image confidence matrix
+     */
+    float *cm;
+
+    /**
+     * Markup for image editing
+     */
+    int *labelField;
+
+
+    /**
+     * Our signature limits
+     */
+    float limits[3];
+
+    /**
+     * Maximum distance of two lab values.
+     */
+    float clusterSize;
+
+    /**
+     *  Initialize the Siox engine to its 'pristine' state.
+     *  Performed at the beginning of extractForeground().
+     */
+    void init();
+
+    /**
+     *  Clean up any debris from processing.
+     */
+    void cleanup();
+
+    /**
+     * Error logging
+     */
+    void error(const char *fmt, ...) G_GNUC_PRINTF(2,3);
+
+    /**
+     * Trace logging
+     */
+    void trace(const char *fmt, ...) G_GNUC_PRINTF(2,3);
+
+    /**
+     *  Stage 1 of the color signature work.  'dims' will be either
+     *  2 for grays, or 3 for colors
+     */
+    void colorSignatureStage1(CieLab *points,
+                              unsigned int leftBase,
+                              unsigned int rightBase,
+                              unsigned int recursionDepth,
+                              unsigned int *clusters,
+                              const unsigned int dims);
+
+    /**
+     *  Stage 2 of the color signature work
+     */
+    void colorSignatureStage2(CieLab         *points,
+                              unsigned int leftBase,
+                              unsigned int rightBase,
+                              unsigned int recursionDepth,
+                              unsigned int *clusters,
+                              const float  threshold,
+                              const unsigned int dims);
+
+    /**
+     *  Main color signature method
+     */
+    bool colorSignature(const std::vector<CieLab> &inputVec,
+                        std::vector<CieLab> &result,
+                        const unsigned int dims);
+
+
+    /**
+     *
+     */
+    void keepOnlyLargeComponents(float threshold,
+                                 double sizeFactorToKeep);
+
+    /**
+     *
+     */
+    int depthFirstSearch(int startPos, float threshold, int curLabel);
+
+
+    /**
+     *
+     */
+    void fillColorRegions();
+
+    /**
+     * Applies the morphological dilate operator.
+     *
+     * Can be used to close small holes in the given confidence matrix.
+     */
+    void dilate(float *cm, int xres, int yres);
+
+    /**
+     * Applies the morphological erode operator.
+     */
+    void erode(float *cm, int xres, int yres);
+
+    /**
+     * Normalizes the matrix to values to [0..1].
+     */
+    void normalizeMatrix(float *cm, int cmSize);
+
+    /**
+     * Multiplies matrix with the given scalar.
+     */
+    void premultiplyMatrix(float alpha, float *cm, int cmSize);
+
+    /**
+     * Blurs confidence matrix with a given symmetrically weighted kernel.
+     */
+    void smooth(float *cm, int xres, int yres,
+                  float f1, float f2, float f3);
+
+    /**
+     * Squared Euclidean distance of p and q.
+     */
+    float sqrEuclideanDist(float *p, int pSize, float *q);
+
+};
+
+
+
+
+} // namespace siox
+} // namespace org
+
+#endif // SEEN_SIOX_H
+//########################################################################
+//#  E N D    O F    F I L E
+//########################################################################
diff --git a/src/trace/trace.cpp b/src/trace/trace.cpp
new file mode 100644
index 0000000..802f497
--- /dev/null
+++ b/src/trace/trace.cpp
@@ -0,0 +1,584 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * A generic interface for plugging different
+ *  autotracers into Inkscape.
+ *
+ * Authors:
+ *   Bob Jamison <rjamison@earthlink.net>
+ *   Jon A. Cruz <jon@joncruz.org>
+ *   Abhishek Sharma
+ *
+ * Copyright (C) 2004-2006 Bob Jamison
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "trace/potrace/inkscape-potrace.h"
+
+#include <limits>
+
+#include <glibmm/i18n.h>
+#include <gtkmm/main.h>
+
+#include <2geom/transforms.h>
+
+#include "desktop.h"
+#include "document.h"
+#include "document-undo.h"
+#include "inkscape.h"
+#include "message-stack.h"
+#include "selection.h"
+
+#include "display/cairo-utils.h"
+#include "display/drawing.h"
+#include "display/drawing-shape.h"
+
+#include "object/sp-item.h"
+#include "object/sp-shape.h"
+#include "object/sp-image.h"
+
+#include "ui/icon-names.h"
+
+#include "xml/repr.h"
+#include "xml/attribute-record.h"
+
+#include "siox.h"
+
+namespace Inkscape {
+namespace Trace {
+
+SPImage *Tracer::getSelectedSPImage()
+{
+
+    SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+    if (!desktop)
+        {
+        g_warning("Trace: No active desktop");
+        return nullptr;
+        }
+
+    Inkscape::MessageStack *msgStack = desktop->getMessageStack();
+
+    Inkscape::Selection *sel = desktop->getSelection();
+    if (!sel)
+        {
+        char *msg = _("Select an <b>image</b> to trace");
+        msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+        //g_warning(msg);
+        return nullptr;
+        }
+
+    if (sioxEnabled)
+        {
+        SPImage *img = nullptr;
+        auto list = sel->items();
+        std::vector<SPItem *> items;
+        sioxShapes.clear();
+
+        /*
+           First, things are selected top-to-bottom, so we need to invert
+           them as bottom-to-top so that we can discover the image and any
+           SPItems above it
+        */
+        for (auto i=list.begin() ; list.end()!=i ; ++i)
+            {
+            if (!SP_IS_ITEM(*i))
+                {
+                continue;
+                }
+            SPItem *item = *i;
+            items.insert(items.begin(), item);
+            }
+        std::vector<SPItem *>::iterator iter;
+        for (iter = items.begin() ; iter!= items.end() ; ++iter)
+            {
+            SPItem *item = *iter;
+            if (SP_IS_IMAGE(item))
+                {
+                if (img) //we want only one
+                    {
+                    char *msg = _("Select only one <b>image</b> to trace");
+                    msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+                    return nullptr;
+                    }
+                img = SP_IMAGE(item);
+                }
+            else // if (img) //# items -after- the image in tree (above it in Z)
+                {
+                if (SP_IS_SHAPE(item))
+                    {
+                    SPShape *shape = SP_SHAPE(item);
+                    sioxShapes.push_back(shape);
+                    }
+                }
+            }
+
+        if (!img || sioxShapes.size() < 1)
+            {
+            char *msg = _("Select one image and one or more shapes above it");
+            msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+            return nullptr;
+            }
+        return img;
+        }
+    else
+        //### SIOX not enabled.  We want exactly one image selected
+        {
+        SPItem *item = sel->singleItem();
+        if (!item)
+            {
+            char *msg = _("Select an <b>image</b> to trace");  //same as above
+            msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+            //g_warning(msg);
+            return nullptr;
+            }
+
+        if (!SP_IS_IMAGE(item))
+            {
+            char *msg = _("Select an <b>image</b> to trace");
+            msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+            //g_warning(msg);
+            return nullptr;
+            }
+
+        SPImage *img = SP_IMAGE(item);
+
+        return img;
+        }
+
+}
+
+
+
+typedef org::siox::SioxImage SioxImage;
+typedef org::siox::SioxObserver SioxObserver;
+typedef org::siox::Siox Siox;
+
+
+class TraceSioxObserver : public SioxObserver
+{
+public:
+
+    /**
+     *
+     */
+    TraceSioxObserver (void *contextArg) :
+                     SioxObserver(contextArg)
+        {}
+
+    /**
+     *
+     */
+    ~TraceSioxObserver () override
+        = default;
+
+    /**
+     *  Informs the observer how much has been completed.
+     *  Return false if the processing should be aborted.
+     */
+    bool progress(float /*percentCompleted*/) override
+        {
+        //Tracer *tracer = (Tracer *)context;
+        //## Allow the GUI to update
+        Gtk::Main::iteration(false); //at least once, non-blocking
+        while( Gtk::Main::events_pending() )
+            Gtk::Main::iteration();
+        return true;
+        }
+
+    /**
+     *  Send an error string to the Observer.  Processing will
+     *  be halted.
+     */
+    void error(const std::string &/*msg*/) override
+        {
+        //Tracer *tracer = (Tracer *)context;
+        }
+
+
+};
+
+
+
+
+
+Glib::RefPtr<Gdk::Pixbuf> Tracer::sioxProcessImage(SPImage *img, Glib::RefPtr<Gdk::Pixbuf>origPixbuf)
+{
+    if (!sioxEnabled)
+        return origPixbuf;
+
+    if (origPixbuf == lastOrigPixbuf)
+        return lastSioxPixbuf;
+
+    //g_message("siox: start");
+
+    SioxImage simage(origPixbuf->gobj());
+
+    SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+    if (!desktop)
+        {
+        g_warning("%s", _("Trace: No active desktop"));
+        return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+        }
+
+    Inkscape::MessageStack *msgStack = desktop->getMessageStack();
+
+    Inkscape::Selection *sel = desktop->getSelection();
+    if (!sel)
+        {
+        char *msg = _("Select an <b>image</b> to trace");
+        msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+        //g_warning(msg);
+        return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+        }
+
+    Inkscape::DrawingItem *aImg = img->get_arenaitem(desktop->dkey);
+    //g_message("img: %d %d %d %d\n", aImg->bbox.x0, aImg->bbox.y0,
+    //                                aImg->bbox.x1, aImg->bbox.y1);
+
+    double width  = aImg->geometricBounds()->width();
+    double height = aImg->geometricBounds()->height();
+
+    double iwidth  = simage.getWidth();
+    double iheight = simage.getHeight();
+
+    double iwscale = width  / iwidth;
+    double ihscale = height / iheight;
+
+    std::vector<Inkscape::DrawingItem *> arenaItems;
+    std::vector<SPShape *>::iterator iter;
+    for (iter = sioxShapes.begin() ; iter!=sioxShapes.end() ; ++iter)
+        {
+        SPItem *item = *iter;
+        Inkscape::DrawingItem *aItem = item->get_arenaitem(desktop->dkey);
+        arenaItems.push_back(aItem);
+        }
+
+    //g_message("%d arena items\n", arenaItems.size());
+
+    //g_message("siox: start selection");
+
+    for (int row=0 ; row<iheight ; row++)
+        {
+        double ypos = aImg->geometricBounds()->top() + ihscale * (double) row;
+        for (int col=0 ; col<simage.getWidth() ; col++)
+            {
+            //Get absolute X,Y position
+            double xpos = aImg->geometricBounds()->left() + iwscale * (double)col;
+            Geom::Point point(xpos, ypos);
+            point *= aImg->transform();
+            //point *= imgMat;
+            //point = desktop->doc2dt(point);
+            //g_message("x:%f    y:%f\n", point[0], point[1]);
+            bool weHaveAHit = false;
+            std::vector<Inkscape::DrawingItem *>::iterator aIter;
+            for (aIter = arenaItems.begin() ; aIter!=arenaItems.end() ; ++aIter)
+                {
+                Inkscape::DrawingItem *arenaItem = *aIter;
+                arenaItem->drawing().update();
+                if (arenaItem->pick(point, 1.0f, 1))
+                    {
+                    weHaveAHit = true;
+                    break;
+                    }
+                }
+
+            if (weHaveAHit)
+                {
+                //g_message("hit!\n");
+                simage.setConfidence(col, row,
+                        Siox::UNKNOWN_REGION_CONFIDENCE);
+                }
+            else
+                {
+                //g_message("miss!\n");
+                simage.setConfidence(col, row,
+                        Siox::CERTAIN_BACKGROUND_CONFIDENCE);
+                }
+            }
+        }
+
+    //g_message("siox: selection done");
+
+    //## ok we have our pixel buf
+    TraceSioxObserver observer(this);
+    Siox sengine(&observer);
+    SioxImage result = sengine.extractForeground(simage, 0xffffff);
+    if (!result.isValid())
+        {
+        g_warning("%s", _("Invalid SIOX result"));
+        return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+        }
+
+    //result.writePPM("siox2.ppm");
+
+    Glib::RefPtr<Gdk::Pixbuf> newPixbuf = Glib::wrap(result.getGdkPixbuf());
+
+    //g_message("siox: done");
+
+    lastSioxPixbuf = newPixbuf;
+
+    return newPixbuf;
+}
+
+
+Glib::RefPtr<Gdk::Pixbuf> Tracer::getSelectedImage()
+{
+
+
+    SPImage *img = getSelectedSPImage();
+    if (!img)
+        return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+
+    if (!img->pixbuf)
+        return Glib::RefPtr<Gdk::Pixbuf>(nullptr);
+
+    GdkPixbuf *raw_pb = img->pixbuf->getPixbufRaw(false);
+    GdkPixbuf *trace_pb = gdk_pixbuf_copy(raw_pb);
+    if (img->pixbuf->pixelFormat() == Inkscape::Pixbuf::PF_CAIRO) {
+        convert_pixels_argb32_to_pixbuf(
+            gdk_pixbuf_get_pixels(trace_pb),
+            gdk_pixbuf_get_width(trace_pb),
+            gdk_pixbuf_get_height(trace_pb),
+            gdk_pixbuf_get_rowstride(trace_pb));
+    }
+
+    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Glib::wrap(trace_pb, false);
+
+    if (sioxEnabled)
+        {
+        Glib::RefPtr<Gdk::Pixbuf> sioxPixbuf =
+             sioxProcessImage(img, pixbuf);
+        if (!sioxPixbuf)
+            {
+            return pixbuf;
+            }
+        else
+            {
+            return sioxPixbuf;
+            }
+        }
+    else
+        {
+        return pixbuf;
+        }
+
+}
+
+
+
+//#########################################################################
+//#  T R A C E
+//#########################################################################
+
+void Tracer::enableSiox(bool enable)
+{
+    sioxEnabled = enable;
+}
+
+
+void Tracer::traceThread()
+{
+    //## Remember. NEVER leave this method without setting
+    //## engine back to NULL
+
+    //## Prepare our kill flag.  We will watch this later to
+    //## see if the main thread wants us to stop
+    keepGoing = true;
+
+    SPDesktop *desktop = SP_ACTIVE_DESKTOP;
+    if (!desktop)
+        {
+        g_warning("Trace: No active desktop\n");
+        return;
+        }
+
+    Inkscape::MessageStack *msgStack = desktop->getMessageStack();
+
+    Inkscape::Selection *selection = desktop->getSelection();
+
+    if (!SP_ACTIVE_DOCUMENT)
+        {
+        char *msg = _("Trace: No active document");
+        msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+        //g_warning(msg);
+        engine = nullptr;
+        return;
+        }
+    SPDocument *doc = SP_ACTIVE_DOCUMENT;
+    doc->ensureUpToDate();
+
+
+    SPImage *img = getSelectedSPImage();
+    if (!img)
+        {
+        engine = nullptr;
+        return;
+        }
+
+    GdkPixbuf *trace_pb = gdk_pixbuf_copy(img->pixbuf->getPixbufRaw(false));
+    if (img->pixbuf->pixelFormat() == Inkscape::Pixbuf::PF_CAIRO) {
+        convert_pixels_argb32_to_pixbuf(
+            gdk_pixbuf_get_pixels(trace_pb),
+            gdk_pixbuf_get_width(trace_pb),
+            gdk_pixbuf_get_height(trace_pb),
+            gdk_pixbuf_get_rowstride(trace_pb));
+    }
+
+    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Glib::wrap(trace_pb, false);
+
+    pixbuf = sioxProcessImage(img, pixbuf);
+
+    if (!pixbuf)
+        {
+        char *msg = _("Trace: Image has no bitmap data");
+        msgStack->flash(Inkscape::ERROR_MESSAGE, msg);
+        //g_warning(msg);
+        engine = nullptr;
+        return;
+        }
+
+    msgStack->flash(Inkscape::NORMAL_MESSAGE, _("Trace: Starting trace..."));
+    desktop->updateCanvasNow();
+
+    std::vector<TracingEngineResult> results =
+                engine->trace(pixbuf);
+    //printf("nrPaths:%d\n", results.size());
+    int nrPaths = results.size();
+
+    //### Check if we should stop
+    if (!keepGoing || nrPaths<1)
+        {
+        engine = nullptr;
+        return;
+        }
+
+    //### Get pointers to the <image> and its parent
+    //XML Tree being used directly here while it shouldn't be.
+    Inkscape::XML::Node *imgRepr   = img->getRepr();
+    Inkscape::XML::Node *par       = imgRepr->parent();
+
+    //### Get some information for the new transform()
+    double x = imgRepr->getAttributeDouble("x", 0.0);
+    double y = imgRepr->getAttributeDouble("y", 0.0);
+    double width = imgRepr->getAttributeDouble("width", 0.0);
+    double height = imgRepr->getAttributeDouble("height", 0.0);
+
+    double iwidth  = (double)pixbuf->get_width();
+    double iheight = (double)pixbuf->get_height();
+
+    double iwscale = width  / iwidth;
+    double ihscale = height / iheight;
+
+    Geom::Translate trans(x, y);
+    Geom::Scale scal(iwscale, ihscale);
+
+    //# Convolve scale, translation, and the original transform
+    Geom::Affine tf(scal * trans);
+    tf *= img->transform;
+
+
+    //#OK.  Now let's start making new nodes
+
+    Inkscape::XML::Document *xml_doc = desktop->doc()->getReprDoc();
+    Inkscape::XML::Node *groupRepr = nullptr;
+
+    //# if more than 1, make a <g>roup of <path>s
+    if (nrPaths > 1)
+        {
+        groupRepr = xml_doc->createElement("svg:g");
+        par->addChild(groupRepr, imgRepr);
+        }
+
+    long totalNodeCount = 0L;
+
+    for (auto result : results)
+        {
+        totalNodeCount += result.getNodeCount();
+
+        Inkscape::XML::Node *pathRepr = xml_doc->createElement("svg:path");
+        pathRepr->setAttributeOrRemoveIfEmpty("style", result.getStyle());
+        pathRepr->setAttributeOrRemoveIfEmpty("d",     result.getPathData());
+
+        if (nrPaths > 1)
+            groupRepr->addChild(pathRepr, nullptr);
+        else
+            par->addChild(pathRepr, imgRepr);
+
+        //### Apply the transform from the image to the new shape
+        SPObject *reprobj = doc->getObjectByRepr(pathRepr);
+        if (reprobj)
+            {
+            SPItem *newItem = SP_ITEM(reprobj);
+            newItem->doWriteTransform(tf);
+            }
+        if (nrPaths == 1)
+            {
+            selection->clear();
+            selection->add(pathRepr);
+            }
+        Inkscape::GC::release(pathRepr);
+        }
+
+    // If we have a group, then focus on, then forget it
+    if (nrPaths > 1)
+        {
+        selection->clear();
+        selection->add(groupRepr);
+        Inkscape::GC::release(groupRepr);
+        }
+
+    //## inform the document, so we can undo
+    DocumentUndo::done(doc, _("Trace bitmap"), INKSCAPE_ICON("bitmap-trace"));
+
+    engine = nullptr;
+
+    char *msg = g_strdup_printf(_("Trace: Done. %ld nodes created"), totalNodeCount);
+    msgStack->flash(Inkscape::NORMAL_MESSAGE, msg);
+    g_free(msg);
+
+}
+
+
+
+
+
+void Tracer::trace(TracingEngine *theEngine)
+{
+    //Check if we are already running
+    if (engine)
+        return;
+
+    engine = theEngine;
+
+    traceThread();
+}
+
+
+
+
+
+void Tracer::abort()
+{
+
+    //## Inform Trace's working thread
+    keepGoing = false;
+
+    if (engine)
+        {
+        engine->abort();
+        }
+
+}
+
+
+
+} // namespace Trace
+
+} // namespace Inkscape
+
+
+//#########################################################################
+//# E N D   O F   F I L E
+//#########################################################################
+
diff --git a/src/trace/trace.h b/src/trace/trace.h
new file mode 100644
index 0000000..ddc4b96
--- /dev/null
+++ b/src/trace/trace.h
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Authors:
+ *   Bob Jamison <rjamison@titan.com>
+ *
+ * Copyright (C) 2004-2006 Bob Jamison
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#ifndef SEEN_TRACE_H
+#define SEEN_TRACE_H
+
+# include <cstring>
+
+#include <glibmm/refptr.h>
+#include <gdkmm/pixbuf.h>
+#include <utility>
+#include <vector>
+
+class SPImage;
+class SPItem;
+class SPShape;
+
+namespace Inkscape {
+
+namespace Trace {
+
+
+
+/**
+ *
+ */
+class TracingEngineResult
+{
+
+public:
+
+    /**
+     *
+     */
+    TracingEngineResult(std::string theStyle,
+                        std::string thePathData,
+                        long theNodeCount) :
+	    style(std::move(theStyle)),
+	    pathData(std::move(thePathData)),
+	    nodeCount(theNodeCount)
+        {}
+
+    TracingEngineResult(const TracingEngineResult &other)
+        { assign(other); }
+
+    virtual TracingEngineResult &operator=(const TracingEngineResult &other)
+        { assign(other); return *this; }
+
+
+    /**
+     *
+     */
+    virtual ~TracingEngineResult()
+        = default;
+
+
+    /**
+     *
+     */
+    std::string getStyle()
+        { return style; }
+
+    /**
+     *
+     */
+    std::string getPathData()
+        { return pathData; }
+
+    /**
+     *
+     */
+    long getNodeCount()
+        { return nodeCount; }
+
+private:
+
+    void assign(const TracingEngineResult &other)
+        {
+        style = other.style;
+        pathData = other.pathData;
+        nodeCount = other.nodeCount;
+        }
+
+    std::string style;
+
+    std::string pathData;
+
+    long nodeCount;
+
+};
+
+
+
+/**
+ * A generic interface for plugging different
+ *  autotracers into Inkscape.
+ */
+class TracingEngine
+{
+
+    public:
+
+    /**
+     *
+     */
+    TracingEngine()
+        = default;
+
+    /**
+     *
+     */
+    virtual ~TracingEngine()
+        = default;
+
+    /**
+     *  This is the working method of this interface, and all
+     *  implementing classes.  Take a GdkPixbuf, trace it, and
+     *  return a style attribute and the path data that is
+     *  compatible with the d="" attribute
+     *  of an SVG <path> element.
+     */
+    virtual  std::vector<TracingEngineResult> trace(
+                           Glib::RefPtr<Gdk::Pixbuf> /*pixbuf*/) = 0;
+
+    /**
+     *  Abort the thread that is executing getPathDataFromPixbuf()
+     */
+    virtual void abort() = 0;
+
+
+
+};//class TracingEngine
+
+
+
+
+
+
+
+
+
+/**
+ *  This simple class allows a generic wrapper around a given
+ *  TracingEngine object.  Its purpose is to provide a gateway
+ *  to a variety of tracing engines, while maintaining a
+ *  consistent interface.
+ */
+class Tracer
+{
+
+public:
+
+
+    /**
+     *
+     */
+    Tracer()
+        {
+        engine       = nullptr;
+        sioxEnabled  = false;
+        }
+
+
+
+    /**
+     *
+     */
+    ~Tracer()
+        = default;
+
+
+    /**
+     *  A convenience method to allow other software to 'see' the
+     *  same image that this class sees.
+     */
+    Glib::RefPtr<Gdk::Pixbuf> getSelectedImage();
+
+    /**
+     * This is the main working method.  Trace the selected image, if
+     * any, and create a <path> element from it, inserting it into
+     * the current document.
+     */
+    void trace(TracingEngine *engine);
+
+
+    /**
+     *  Abort the thread that is executing convertImageToPath()
+     */
+    void abort();
+
+    /**
+     *  Whether we want to enable SIOX subimage selection.
+     */
+    void enableSiox(bool enable);
+
+
+private:
+
+    /**
+     * This is the single path code that is called by its counterpart above.
+     * Threaded method that does single bitmap--->path conversion.
+     */
+    void traceThread();
+
+    /**
+     * This is true during execution. Setting it to false (like abort()
+     * does) should inform the threaded code that it needs to stop
+     */
+    bool keepGoing;
+
+    /**
+     *  During tracing, this is Non-null, and refers to the
+     *  engine that is currently doing the tracing.
+     */
+    TracingEngine *engine;
+
+    /**
+     * Get the selected image.  Also check for any SPItems over it, in
+     * case the user wants SIOX pre-processing.
+     */
+    SPImage *getSelectedSPImage();
+
+    std::vector<SPShape *> sioxShapes;
+
+    bool sioxEnabled;
+
+    /**
+     * Process a GdkPixbuf, according to which areas have been
+     * obscured in the GUI.
+     */
+    Glib::RefPtr<Gdk::Pixbuf> sioxProcessImage(SPImage *img, Glib::RefPtr<Gdk::Pixbuf> origPixbuf);
+
+    Glib::RefPtr<Gdk::Pixbuf> lastSioxPixbuf;
+    Glib::RefPtr<Gdk::Pixbuf> lastOrigPixbuf;
+
+};//class Tracer
+
+
+
+
+} // namespace Trace
+
+} // namespace Inkscape
+
+
+
+#endif // SEEN_TRACE_H
+
+//#########################################################################
+//# E N D   O F   F I L E
+//#########################################################################
+