blob: 92b39d3a476201901ccad1e62228ecfc5ebc1d2d [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_ANIMATED(SkPath_quadTo_example_parametric_animated, 512, 512, false, 0, 4) {
// SkPath_quadTo_example_parametric_animated
SkPoint quad(SkPoint p0, SkPoint p1, SkPoint p2, float t) {
float s = 1 - t;
return {(s * s * p0.x()) + (2 * s * t * p1.x()) + (t * t * p2.x()),
(s * s * p0.y()) + (2 * s * t * p1.y()) + (t * t * p2.y())};
}
/*
If the starting point is (x0, y0), then this curve is defined as the
paramentric curve as `t` goes from 0 to 1:
s := 1 - t
x := (s * s * x0) + (2 * s * t * x1) + (t * t * x2)
y := (s * s * y0) + (2 * s * t * y1) + (t * t * y2)
*/
static SkPoint interpolate(SkPoint a, SkPoint b, float t) {
return {SkScalarInterp(a.x(), b.x(), t),
SkScalarInterp(a.y(), b.y(), t)};
}
static void draw_line(SkCanvas* canvas, SkPoint p0, SkPoint p1, const SkPaint& paint) {
canvas->drawLine(p0.x(), p0.y(), p1.x(), p1.y(), paint);
}
static void draw_point(SkCanvas* canvas, SkPoint p, const SkPaint& paint) {
canvas->drawPoint(p.x(), p.y(), paint);
}
void draw(SkCanvas* canvas) {
canvas->clear(SkColorSetARGB(255,255,255,255));
SkPaint paint;
paint.setAntiAlias(true);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(5);
SkPoint a{10, 100};
SkPoint b{200, 400};
SkPoint c{390, 100};
SkPoint ab = interpolate(a, b, frame);
SkPoint bc = interpolate(b, c, frame);
draw_line(canvas, a, b, paint);
draw_line(canvas, b, c, paint);
paint.setStrokeWidth(1);
draw_line(canvas, ab, bc, paint);
paint.setStrokeWidth(5);
paint.setColor(SkColorSetARGB(255,0,0,255));
SkPath quadraticCurve;
quadraticCurve.moveTo(a);
quadraticCurve.quadTo(b, c);
canvas->drawPath(quadraticCurve, paint);
SkPaint textPaint;
SkFont font(nullptr, 32);
textPaint.setAntiAlias(true);
canvas->drawString("a", a.x(), a.y(), font, textPaint);
canvas->drawString("b", b.x()+20, b.y()+20, font, textPaint);
canvas->drawString("c", c.x(), c.y(), font, textPaint);
SkPaint pointPaint;
pointPaint.setAntiAlias(true);
pointPaint.setStrokeWidth(8);
pointPaint.setStrokeCap(SkPaint::kRound_Cap);
pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0));
draw_point(canvas, quad(a, b, c, frame), pointPaint);
}
} // END FIDDLE