| // 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, std::size(pts)), p); |
| |
| p.setStrokeWidth(10); |
| p.setColor(SK_ColorBLACK); |
| canvas->drawPoints(SkCanvas::kPoints_PointMode, std::size(pts), pts, p); |
| } |
| } // END FIDDLE |