add more docs/examples from named fiddles.
ignore offscreen, srgb, and animated fiddles for now.
Change-Id: I923131b684865698e6cda138b004930e11f504d5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263713
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
diff --git a/docs/examples/SmoothBezierSplineInterpolation.cpp b/docs/examples/SmoothBezierSplineInterpolation.cpp
new file mode 100644
index 0000000..4486815
--- /dev/null
+++ b/docs/examples/SmoothBezierSplineInterpolation.cpp
@@ -0,0 +1,82 @@
+// Copyright 2020 Google LLC.
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+#include "tools/fiddle/examples.h"
+REG_FIDDLE(SmoothBezierSplineInterpolation, 1024, 1024, false, 0) {
+// Smooth Bézier Spline Interpolation
+
+SkPath MakeCubicSplineInterpolation(const SkPoint* pts, size_t N) {
+ // Code borrowed from https://www.particleincell.com/2012/bezier-splines/
+
+ SkPath path;
+ if (N < 2) {
+ return path;
+ }
+ if (N == 2) {
+ path.moveTo(pts[0]);
+ path.lineTo(pts[1]);
+ return path;
+ }
+ size_t n = N - 1; // number of segments
+ struct Scratch {
+ SkPoint a, b, c, r, p;
+ };
+ // Can I do this will less allocation?
+ std::unique_ptr<Scratch[]> s(new Scratch[n]);
+ s[0].a = {0, 0};
+ s[0].b = {2, 2};
+ s[0].c = {1, 1};
+ s[0].r = {pts[0].x() + 2 * pts[1].x(), pts[0].y() + 2 * pts[1].y()};
+ for (size_t i = 1; i < n - 1; ++i) {
+ s[i].a = {1, 1};
+ s[i].b = {4, 4};
+ s[i].c = {1, 1};
+ s[i].r = {4 * pts[i].x() + 2 * pts[i + 1].x(), 4 * pts[i].y() + 2 * pts[i + 1].y()};
+ }
+ s[n - 1].a = {2, 2};
+ s[n - 1].b = {7, 7};
+ s[n - 1].c = {0, 0};
+ s[n - 1].r = {8 * pts[n - 1].x() + pts[N - 1].x(), 8 * pts[n - 1].y() + pts[N - 1].y()};
+ for (size_t i = 1; i < n; i++) {
+ float mx = s[i].a.x() / s[i - 1].b.x();
+ float my = s[i].a.y() / s[i - 1].b.y();
+ s[i].b -= {mx * s[i - 1].c.x(), my * s[i - 1].c.y()};
+ s[i].r -= {mx * s[i - 1].r.x(), my * s[i - 1].r.y()};
+ }
+ s[n - 1].p = {s[n - 1].r.x() / s[n - 1].b.x(), s[n - 1].r.y() / s[n - 1].b.y()};
+ for (int i = (int)N - 3; i >= 0; --i) {
+ s[i].p = {(s[i].r.x() - s[i].c.x() * s[i + 1].p.fX) / s[i].b.x(),
+ (s[i].r.y() - s[i].c.y() * s[i + 1].p.fY) / s[i].b.y()};
+ }
+
+ path.moveTo(pts[0]);
+ for (size_t i = 0; i < n - 1; i++) {
+ SkPoint q = {2 * pts[i + 1].x() - s[i + 1].p.fX, 2 * pts[i + 1].y() - s[i + 1].p.fY};
+ path.cubicTo(s[i].p, q, pts[i + 1]);
+ }
+ SkPoint q = {0.5f * (pts[N - 1].x() + s[n - 1].p.x()),
+ 0.5f * (pts[N - 1].y() + s[n - 1].p.y())};
+ path.cubicTo(s[n - 1].p, q, pts[n]);
+ return path;
+}
+
+void draw(SkCanvas* canvas) {
+ SkPaint p;
+ p.setColor(SK_ColorRED);
+ p.setAntiAlias(true);
+ p.setStyle(SkPaint::kStroke_Style);
+ p.setStrokeWidth(3);
+ p.setStrokeCap(SkPaint::kRound_Cap);
+
+ // randomly generated y values in range [12,1024].
+ SkPoint pts[] = {
+ {62, 511}, {162, 605}, {262, 610}, {362, 402}, {462, 959},
+ {562, 58}, {662, 272}, {762, 99}, {862, 759}, {962, 945},
+ };
+
+ canvas->drawPath(MakeCubicSplineInterpolation(pts, SK_ARRAY_COUNT(pts)), p);
+
+ p.setStrokeWidth(10);
+ p.setColor(SK_ColorBLACK);
+ canvas->drawPoints(SkCanvas::kPoints_PointMode, SK_ARRAY_COUNT(pts), pts, p);
+}
+} // END FIDDLE