| // 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 |