Hal Canary | 8800042 | 2020-01-15 11:51:12 -0500 | [diff] [blame] | 1 | // Copyright 2020 Google LLC. |
| 2 | // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file. |
| 3 | #include "tools/fiddle/examples.h" |
| 4 | REG_FIDDLE_ANIMATED(SkPath_quadTo_example_parametric_animated, 512, 512, false, 0, 4) { |
| 5 | // SkPath_quadTo_example_parametric_animated |
| 6 | |
| 7 | SkPoint quad(SkPoint p0, SkPoint p1, SkPoint p2, float t) { |
| 8 | float s = 1 - t; |
| 9 | return {(s * s * p0.x()) + (2 * s * t * p1.x()) + (t * t * p2.x()), |
| 10 | (s * s * p0.y()) + (2 * s * t * p1.y()) + (t * t * p2.y())}; |
| 11 | } |
| 12 | |
| 13 | /* |
| 14 | |
| 15 | If the starting point is (x0, y0), then this curve is defined as the |
| 16 | paramentric curve as `t` goes from 0 to 1: |
| 17 | |
| 18 | s := 1 - t |
| 19 | x := (s * s * x0) + (2 * s * t * x1) + (t * t * x2) |
| 20 | y := (s * s * y0) + (2 * s * t * y1) + (t * t * y2) |
| 21 | |
| 22 | */ |
| 23 | |
| 24 | static SkPoint interpolate(SkPoint a, SkPoint b, float t) { |
| 25 | return {SkScalarInterp(a.x(), b.x(), t), |
| 26 | SkScalarInterp(a.y(), b.y(), t)}; |
| 27 | } |
| 28 | |
| 29 | static void draw_line(SkCanvas* canvas, SkPoint p0, SkPoint p1, const SkPaint& paint) { |
| 30 | canvas->drawLine(p0.x(), p0.y(), p1.x(), p1.y(), paint); |
| 31 | } |
| 32 | |
| 33 | static void draw_point(SkCanvas* canvas, SkPoint p, const SkPaint& paint) { |
| 34 | canvas->drawPoint(p.x(), p.y(), paint); |
| 35 | } |
| 36 | |
| 37 | void draw(SkCanvas* canvas) { |
| 38 | canvas->clear(SkColorSetARGB(255,255,255,255)); |
| 39 | |
| 40 | SkPaint paint; |
| 41 | paint.setAntiAlias(true); |
| 42 | paint.setStyle(SkPaint::kStroke_Style); |
| 43 | paint.setStrokeWidth(5); |
| 44 | |
| 45 | SkPoint a{10, 100}; |
| 46 | SkPoint b{200, 400}; |
| 47 | SkPoint c{390, 100}; |
| 48 | |
| 49 | SkPoint ab = interpolate(a, b, frame); |
| 50 | SkPoint bc = interpolate(b, c, frame); |
| 51 | |
| 52 | draw_line(canvas, a, b, paint); |
| 53 | draw_line(canvas, b, c, paint); |
| 54 | |
| 55 | paint.setStrokeWidth(1); |
| 56 | draw_line(canvas, ab, bc, paint); |
| 57 | paint.setStrokeWidth(5); |
| 58 | |
| 59 | paint.setColor(SkColorSetARGB(255,0,0,255)); |
| 60 | SkPath quadraticCurve; |
| 61 | quadraticCurve.moveTo(a); |
| 62 | quadraticCurve.quadTo(b, c); |
| 63 | canvas->drawPath(quadraticCurve, paint); |
| 64 | |
| 65 | SkPaint textPaint; |
| 66 | SkFont font(nullptr, 32); |
| 67 | textPaint.setAntiAlias(true); |
| 68 | canvas->drawString("a", a.x(), a.y(), font, textPaint); |
| 69 | canvas->drawString("b", b.x()+20, b.y()+20, font, textPaint); |
| 70 | canvas->drawString("c", c.x(), c.y(), font, textPaint); |
| 71 | |
| 72 | SkPaint pointPaint; |
| 73 | pointPaint.setAntiAlias(true); |
| 74 | pointPaint.setStrokeWidth(8); |
| 75 | pointPaint.setStrokeCap(SkPaint::kRound_Cap); |
| 76 | pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0)); |
| 77 | draw_point(canvas, quad(a, b, c, frame), pointPaint); |
| 78 | } |
| 79 | } // END FIDDLE |