1 files changed, 508 insertions, 0 deletions
diff --git a/src/helper/png-write.cpp b/src/helper/png-write.cpp
new file mode 100644
index 0000000..88ca1a5
--- /dev/null
+++ b/src/helper/png-write.cpp
@@ -0,0 +1,508 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PNG file format utilities
+ *
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *   Whoever wrote this example in libpng documentation
+ *   Peter Bostrom
+ *   Jon A. Cruz <jon@joncruz.org>
+ *   Abhishek Sharma
+ *
+ * Copyright (C) 1999-2002 authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+
+#include <2geom/rect.h>
+#include <2geom/transforms.h>
+
+#include <png.h>
+
+#include "document.h"
+#include "inkscape.h"
+#include "png-write.h"
+#include "preferences.h"
+#include "rdf.h"
+
+#include "display/cairo-utils.h"
+#include "display/drawing-context.h"
+#include "display/drawing.h"
+
+#include "io/sys.h"
+
+#include "object/sp-defs.h"
+#include "object/sp-item.h"
+#include "object/sp-root.h"
+
+#include "ui/interface.h"
+#include "util/units.h"
+
+/* This is an example of how to use libpng to read and write PNG files.
+ * The file libpng.txt is much more verbose then this.  If you have not
+ * read it, do so first.  This was designed to be a starting point of an
+ * implementation.  This is not officially part of libpng, and therefore
+ * does not require a copyright notice.
+ *
+ * This file does not currently compile, because it is missing certain
+ * parts, like allocating memory to hold an image.  You will have to
+ * supply these parts to get it to compile.  For an example of a minimal
+ * working PNG reader/writer, see pngtest.c, included in this distribution.
+ */
+
+struct SPEBP {
+    unsigned long int width, height, sheight;
+    guint32 background;
+    Inkscape::Drawing *drawing; // it is assumed that all unneeded items are hidden
+    guchar *px;
+    unsigned (*status)(float, void *);
+    void *data;
+};
+
+/* write a png file */
+
+struct SPPNGBD {
+    guchar const *px;
+    int rowstride;
+};
+
+/**
+ * A simple wrapper to list png_text.
+ */
+class PngTextList {
+public:
+    PngTextList() : count(0), textItems(nullptr) {}
+    ~PngTextList();
+
+    void add(gchar const* key, gchar const* text);
+    gint getCount() {return count;}
+    png_text* getPtext() {return textItems;}
+
+private:
+    gint count;
+    png_text* textItems;
+};
+
+PngTextList::~PngTextList() {
+    for (gint i = 0; i < count; i++) {
+        if (textItems[i].key) {
+            g_free(textItems[i].key);
+        }
+        if (textItems[i].text) {
+            g_free(textItems[i].text);
+        }
+    }
+}
+
+void PngTextList::add(gchar const* key, gchar const* text)
+{
+    if (count < 0) {
+        count = 0;
+        textItems = nullptr;
+    }
+    png_text* tmp = (count > 0) ? g_try_renew(png_text, textItems, count + 1): g_try_new(png_text, 1);
+    if (tmp) {
+        textItems = tmp;
+        count++;
+
+        png_text* item = &(textItems[count - 1]);
+        item->compression = PNG_TEXT_COMPRESSION_NONE;
+        item->key = g_strdup(key);
+        item->text = g_strdup(text);
+        item->text_length = 0;
+#ifdef PNG_iTXt_SUPPORTED
+        item->itxt_length = 0;
+        item->lang = nullptr;
+        item->lang_key = nullptr;
+#endif // PNG_iTXt_SUPPORTED
+    } else {
+        g_warning("Unable to allocate array for %d PNG text data.", count);
+        textItems = nullptr;
+        count = 0;
+    }
+}
+
+static bool
+sp_png_write_rgba_striped(SPDocument *doc,
+                          gchar const *filename, unsigned long int width, unsigned long int height, double xdpi, double ydpi,
+                          int (* get_rows)(guchar const **rows, void **to_free, int row, int num_rows, void *data, int color_type, int bit_depth, int antialias),
+                          void *data, bool interlace, int color_type, int bit_depth, int zlib, int antialiasing)
+{
+    g_return_val_if_fail(filename != nullptr, false);
+    g_return_val_if_fail(data != nullptr, false);
+
+    struct SPEBP *ebp = (struct SPEBP *) data;
+    FILE *fp;
+    png_structp png_ptr;
+    png_infop info_ptr;
+    png_color_8 sig_bit;
+    png_uint_32 r;
+
+    /* open the file */
+
+    Inkscape::IO::dump_fopen_call(filename, "M");
+    fp = Inkscape::IO::fopen_utf8name(filename, "wb");
+    if(fp == nullptr) return false;
+
+    /* Create and initialize the png_struct with the desired error handler
+     * functions.  If you want to use the default stderr and longjump method,
+     * you can supply NULL for the last three parameters.  We also check that
+     * the library version is compatible with the one used at compile time,
+     * in case we are using dynamically linked libraries.  REQUIRED.
+     */
+    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+
+    if (png_ptr == nullptr) {
+        fclose(fp);
+        return false;
+    }
+
+    /* Allocate/initialize the image information data.  REQUIRED */
+    info_ptr = png_create_info_struct(png_ptr);
+    if (info_ptr == nullptr) {
+        fclose(fp);
+        png_destroy_write_struct(&png_ptr, nullptr);
+        return false;
+    }
+
+    /* Set error handling.  REQUIRED if you aren't supplying your own
+     * error handling functions in the png_create_write_struct() call.
+     */
+    if (setjmp(png_jmpbuf(png_ptr))) {
+        // If we get here, we had a problem reading the file
+        fclose(fp);
+        png_destroy_write_struct(&png_ptr, &info_ptr);
+        return false;
+    }
+
+    /* set up the output control if you are using standard C streams */
+    png_init_io(png_ptr, fp);
+
+    /* Set the image information here.  Width and height are up to 2^31,
+     * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
+     * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
+     * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
+     * or PNG_COLOR_TYPE_RGB_ALPHA.  interlace is either PNG_INTERLACE_NONE or
+     * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
+     * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
+     */
+
+    png_set_compression_level(png_ptr, zlib);
+
+    png_set_IHDR(png_ptr, info_ptr,
+                 width,
+                 height,
+                 bit_depth,
+                 color_type,
+                 interlace ? PNG_INTERLACE_ADAM7 : PNG_INTERLACE_NONE,
+                 PNG_COMPRESSION_TYPE_BASE,
+                 PNG_FILTER_TYPE_BASE);
+
+    if ((color_type&2) && bit_depth == 16) {
+        // otherwise, if we are dealing with a color image then
+        sig_bit.red = 8;
+        sig_bit.green = 8;
+        sig_bit.blue = 8;
+        // if the image has an alpha channel then
+        if (color_type&4)
+            sig_bit.alpha = 8;
+        png_set_sBIT(png_ptr, info_ptr, &sig_bit);
+    }
+
+    PngTextList textList;
+
+    textList.add("Software", "www.inkscape.org"); // Made by Inkscape comment
+    {
+        const gchar* pngToDc[] = {"Title", "title",
+                               "Author", "creator",
+                               "Description", "description",
+                               //"Copyright", "",
+                               "Creation Time", "date",
+                               //"Disclaimer", "",
+                               //"Warning", "",
+                               "Source", "source"
+                               //"Comment", ""
+        };
+        for (size_t i = 0; i < G_N_ELEMENTS(pngToDc); i += 2) {
+            struct rdf_work_entity_t * entity = rdf_find_entity ( pngToDc[i + 1] );
+            if (entity) {
+                gchar const* data = rdf_get_work_entity(doc, entity);
+                if (data && *data) {
+                    textList.add(pngToDc[i], data);
+                }
+            } else {
+                g_warning("Unable to find entity [%s]", pngToDc[i + 1]);
+            }
+        }
+
+
+        struct rdf_license_t *license =  rdf_get_license(doc);
+        if (license) {
+            if (license->name && license->uri) {
+                gchar* tmp = g_strdup_printf("%s %s", license->name, license->uri);
+                textList.add("Copyright", tmp);
+                g_free(tmp);
+            } else if (license->name) {
+                textList.add("Copyright", license->name);
+            } else if (license->uri) {
+                textList.add("Copyright", license->uri);
+            }
+        }
+    }
+    if (textList.getCount() > 0) {
+        png_set_text(png_ptr, info_ptr, textList.getPtext(), textList.getCount());
+    }
+
+    /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */
+    /* note that if sRGB is present the cHRM chunk must be ignored
+     * on read and must be written in accordance with the sRGB profile */
+    if(xdpi < 0.0254 ) xdpi = 0.0255;
+    if(ydpi < 0.0254 ) ydpi = 0.0255;
+
+    png_set_pHYs(png_ptr, info_ptr, unsigned(xdpi / 0.0254 ), unsigned(ydpi / 0.0254 ), PNG_RESOLUTION_METER);
+
+    /* Write the file header information.  REQUIRED */
+    png_write_info(png_ptr, info_ptr);
+
+    /* Once we write out the header, the compression type on the text
+     * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or
+     * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again
+     * at the end.
+     */
+
+    /* set up the transformations you want.  Note that these are
+     * all optional.  Only call them if you want them.
+     */
+
+    /* --- CUT --- */
+
+    /* The easiest way to write the image (you may have a different memory
+     * layout, however, so choose what fits your needs best).  You need to
+     * use the first method if you aren't handling interlacing yourself.
+     */
+
+    png_bytep* row_pointers = new png_bytep[ebp->sheight];
+    int number_of_passes = interlace ? png_set_interlace_handling(png_ptr) : 1;
+
+    for(int i=0;i<number_of_passes; ++i){
+        r = 0;
+        while (r < static_cast<png_uint_32>(height)) {
+            void *to_free;
+            int n = get_rows((unsigned char const **) row_pointers, &to_free, r, height-r, data, color_type, bit_depth, antialiasing);
+            if (!n) break;
+            png_write_rows(png_ptr, row_pointers, n);
+            g_free(to_free);
+            r += n;
+        }
+    }
+
+    delete[] row_pointers;
+
+    /* You can write optional chunks like tEXt, zTXt, and tIME at the end
+     * as well.
+     */
+
+    /* It is REQUIRED to call this to finish writing the rest of the file */
+    png_write_end(png_ptr, info_ptr);
+
+    /* if you allocated any text comments, free them here */
+
+    /* clean up after the write, and free any memory allocated */
+    png_destroy_write_struct(&png_ptr, &info_ptr);
+
+    /* close the file */
+    fclose(fp);
+
+    /* that's it */
+    return true;
+}
+
+
+/**
+ *
+ */
+static int
+sp_export_get_rows(guchar const **rows, void **to_free, int row, int num_rows, void *data, int color_type, int bit_depth, int antialiasing)
+{
+    struct SPEBP *ebp = (struct SPEBP *) data;
+
+    if (ebp->status) {
+        if (!ebp->status((float) row / ebp->height, ebp->data)) return 0;
+    }
+
+    num_rows = MIN(num_rows, static_cast<int>(ebp->sheight));
+    num_rows = MIN(num_rows, static_cast<int>(ebp->height - row));
+
+    /* Set area of interest */
+    // bbox is now set to the entire image to prevent discontinuities
+    // in the image when blur is used (the borders may still be a bit
+    // off, but that's less noticeable).
+    Geom::IntRect bbox = Geom::IntRect::from_xywh(0, row, ebp->width, num_rows);
+
+    /* Update to renderable state */
+    ebp->drawing->update(bbox);
+
+    int stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, ebp->width);
+    unsigned char *px = g_new(guchar, num_rows * stride);
+
+    cairo_surface_t *s = cairo_image_surface_create_for_data(
+        px, CAIRO_FORMAT_ARGB32, ebp->width, num_rows, stride);
+    Inkscape::DrawingContext dc(s, bbox.min());
+    dc.setSource(ebp->background);
+    dc.setOperator(CAIRO_OPERATOR_SOURCE);
+    dc.paint();
+    dc.setOperator(CAIRO_OPERATOR_OVER);
+
+    /* Render */
+    ebp->drawing->render(dc, bbox, 0, antialiasing);
+    cairo_surface_destroy(s);
+
+    // PNG stores data as unpremultiplied big-endian RGBA, which means
+    // it's identical to the GdkPixbuf format.
+    convert_pixels_argb32_to_pixbuf(px, ebp->width, num_rows, stride,
+                                    /* RGBA to ARGB with A=0 */ ebp->background >> 8);
+    
+    // If a custom bit depth or color type is asked, then convert rgb to grayscale, etc.
+    const guchar* new_data = pixbuf_to_png(rows, px, num_rows, ebp->width, stride, color_type, bit_depth);
+    *to_free = (void*) new_data;
+    free(px);
+
+    return num_rows;
+}
+
+/**
+ * Hide all items that are not listed in list, recursively, skipping groups and defs.
+ */
+static void hide_other_items_recursively(SPObject *o, const std::vector<SPItem*> &list, unsigned dkey)
+{
+    if ( SP_IS_ITEM(o)
+         && !SP_IS_DEFS(o)
+         && !SP_IS_ROOT(o)
+         && !SP_IS_GROUP(o)
+         && list.end()==find(list.begin(),list.end(),o))
+    {
+        SP_ITEM(o)->invoke_hide(dkey);
+    }
+
+    // recurse
+    if (list.end()==find(list.begin(),list.end(),o)) {
+        for (auto& child: o->children) {
+            hide_other_items_recursively(&child, list, dkey);
+        }
+    }
+}
+
+
+ExportResult sp_export_png_file(SPDocument *doc, gchar const *filename,
+                                double x0, double y0, double x1, double y1,
+                                unsigned long int width, unsigned long int height, double xdpi, double ydpi,
+                                unsigned long bgcolor,
+                                unsigned int (*status) (float, void *),
+                                void *data, bool force_overwrite,
+                                const std::vector<SPItem*> &items_only, bool interlace, int color_type, int bit_depth, int zlib, int antialiasing)
+{
+    return sp_export_png_file(doc, filename, Geom::Rect(Geom::Point(x0,y0),Geom::Point(x1,y1)),
+                              width, height, xdpi, ydpi, bgcolor, status, data, force_overwrite, items_only, interlace, color_type, bit_depth, zlib, antialiasing);
+}
+
+/**
+ * Export an area to a PNG file
+ *
+ * @param area Area in document coordinates
+ */
+ExportResult sp_export_png_file(SPDocument *doc, gchar const *filename,
+                                Geom::Rect const &area,
+                                unsigned long width, unsigned long height, double xdpi, double ydpi,
+                                unsigned long bgcolor,
+                                unsigned (*status)(float, void *),
+                                void *data, bool force_overwrite,
+                                const std::vector<SPItem*> &items_only, bool interlace, int color_type, int bit_depth, int zlib, int antialiasing)
+{
+    g_return_val_if_fail(doc != nullptr, EXPORT_ERROR);
+    g_return_val_if_fail(filename != nullptr, EXPORT_ERROR);
+    g_return_val_if_fail(width >= 1, EXPORT_ERROR);
+    g_return_val_if_fail(height >= 1, EXPORT_ERROR);
+    g_return_val_if_fail(!area.hasZeroArea(), EXPORT_ERROR);
+
+    if (!force_overwrite && !sp_ui_overwrite_file(filename)) {
+        // aborted overwrite
+	return EXPORT_ABORTED;
+    }
+
+    doc->ensureUpToDate();
+
+    /* Calculate translation by transforming to document coordinates (flipping Y)*/
+    Geom::Point translation = -area.min();
+
+    /*  This calculation is only valid when assumed that (x0,y0)= area.corner(0) and (x1,y1) = area.corner(2)
+     * 1) a[0] * x0 + a[2] * y1 + a[4] = 0.0
+     * 2) a[1] * x0 + a[3] * y1 + a[5] = 0.0
+     * 3) a[0] * x1 + a[2] * y1 + a[4] = width
+     * 4) a[1] * x0 + a[3] * y0 + a[5] = height
+     * 5) a[1] = 0.0;
+     * 6) a[2] = 0.0;
+     *
+     * (1,3) a[0] * x1 - a[0] * x0 = width
+     * a[0] = width / (x1 - x0)
+     * (2,4) a[3] * y0 - a[3] * y1 = height
+     * a[3] = height / (y0 - y1)
+     * (1) a[4] = -a[0] * x0
+     * (2) a[5] = -a[3] * y1
+     */
+
+    Geom::Affine const affine(Geom::Translate(translation)
+                            * Geom::Scale(width / area.width(),
+                                        height / area.height()));
+
+    struct SPEBP ebp;
+    ebp.width  = width;
+    ebp.height = height;
+    ebp.background = bgcolor;
+
+    /* Create new drawing */
+    Inkscape::Drawing drawing;
+    drawing.setExact(true); // export with maximum blur rendering quality
+    unsigned const dkey = SPItem::display_key_new(1);
+
+    // Create ArenaItems and set transform
+    drawing.setRoot(doc->getRoot()->invoke_show(drawing, dkey, SP_ITEM_SHOW_DISPLAY));
+    drawing.root()->setTransform(affine);
+    ebp.drawing = &drawing;
+
+    // We show all and then hide all items we don't want, instead of showing only requested items,
+    // because that would not work if the shown item references something in defs
+    if (!items_only.empty()) {
+        hide_other_items_recursively(doc->getRoot(), items_only, dkey);
+    }
+
+    ebp.status = status;
+    ebp.data   = data;
+
+    bool write_status = false;;
+
+    ebp.sheight = 64;
+    ebp.px = g_try_new(guchar, 4 * ebp.sheight * width);
+
+    if (ebp.px) {
+        write_status = sp_png_write_rgba_striped(doc, filename, width, height, xdpi, ydpi, sp_export_get_rows, &ebp, interlace, color_type, bit_depth, zlib, antialiasing);
+        g_free(ebp.px);
+    }
+
+    // Hide items, this releases arenaitem
+    doc->getRoot()->invoke_hide(dkey);
+
+    return write_status ? EXPORT_OK : EXPORT_ERROR;
+}
+
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :