1 files changed, 90 insertions, 0 deletions
diff --git a/src/path/splinefit/bezier-fit.cpp b/src/path/splinefit/bezier-fit.cpp
new file mode 100644
index 0000000..111f538
--- /dev/null
+++ b/src/path/splinefit/bezier-fit.cpp
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <iostream>
+#include <vector>
+#include "bezier-fit.h"
+#include <2geom/bezier-utils.h>
+#include <2geom/point.h>
+
+extern "C" {
+    #include "splinefit.h"
+    #include "splinefont.h"
+}
+
+int bezier_fit(Geom::Point bezier[4], const std::vector<InputPoint>& data) {
+
+    if (data.size() <= 2) return 0;
+
+    int order2 = false; // not 2nd order, so cubic
+    // "Fitting cubic Bézier curves"
+    // https://raphlinus.github.io/curves/2021/03/11/bezier-fitting.html
+    mergetype mt = mt_levien;
+    auto len = data.size();
+
+    std::vector<FitPoint> fit;
+    for (int i = 0; i < len; ++i) {
+        fit.push_back({});
+        auto& fp = fit.back();
+        fp.p.x = data[i].x();
+        fp.p.y = data[i].y();
+        fp.t = data[i].t;
+        fp.ut.x = fp.ut.y = 0;
+    }
+
+    // transform data into spline set format
+
+	auto input = (SplineSet*)chunkalloc(sizeof(SplineSet));
+
+    for (int i = 0; i < len; ++i) {
+        auto& d = data[i];
+		auto sp = SplinePointCreate(d.x(), d.y());
+        if (d.have_slope) {
+            sp->nextcp.x = d.front.x();
+            sp->nextcp.y = d.front.y();
+            sp->nonextcp = false;
+            sp->prevcp.x = d.back.x();
+            sp->prevcp.y = d.back.y();
+            sp->noprevcp = false;
+        }
+
+        if (i == 0) {
+            input->first = input->last = sp; 
+        }
+        else {
+            SplineMake(input->last, sp, order2);
+            input->last = sp;
+        }
+    }
+
+    Spline* spline = ApproximateSplineFromPointsSlopes(input->first, input->last, fit.data(), fit.size(), order2, mt);
+    bool ok = spline != nullptr;
+
+    if (!spline) {
+        std::vector<Geom::Point> inp;
+        inp.reserve(data.size());
+        for (auto& pt : data) {
+            inp.push_back(pt);
+        }
+        ok = bezier_fit_cubic(bezier, inp.data(), inp.size(), 0.5) > 0;
+    }
+
+    if (spline) {
+        bezier[0].x() = spline->from->me.x;
+        bezier[0].y() = spline->from->me.y;
+
+        bezier[1].x() = spline->from->nextcp.x;
+        bezier[1].y() = spline->from->nextcp.y;
+
+        bezier[2].x() = spline->to->prevcp.x;
+        bezier[2].y() = spline->to->prevcp.y;
+
+        bezier[3].x() = spline->to->me.x;
+        bezier[3].y() = spline->to->me.y;
+    }
+
+    SplinePointListFree(input);
+    //TODO: verify that all C structs are freed up
+    // SplineFree(spline);
+
+    return ok;
+}