blob: 4486815b635bb70967c346d4121d76910d683b4a [file] [log] [blame]
// 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 B├ęzier 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