Hal Canary | 6c8422c | 2020-01-10 15:22:09 -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(SkPath_quadTo_example_parametric, 512, 512, false, 0) { |
| 5 | SkPoint quad(SkPoint p0, SkPoint p1, SkPoint p2, float t) { |
| 6 | float s = 1 - t; |
| 7 | return {(s * s * p0.x()) + (2 * s * t * p1.x()) + (t * t * p2.x()), |
| 8 | (s * s * p0.y()) + (2 * s * t * p1.y()) + (t * t * p2.y())}; |
| 9 | } |
| 10 | |
| 11 | /* |
| 12 | |
| 13 | If the starting point is (x0, y0), then this curve is defined as the |
| 14 | paramentric curve as `t` goes from 0 to 1: |
| 15 | |
| 16 | s := 1 - t |
| 17 | x := (s * s * x0) + (2 * s * t * x1) + (t * t * x2) |
| 18 | y := (s * s * y0) + (2 * s * t * y1) + (t * t * y2) |
| 19 | |
| 20 | */ |
| 21 | |
| 22 | void draw(SkCanvas* canvas) { |
| 23 | canvas->clear(SkColorSetARGB(255, 255, 255, 255)); |
| 24 | |
| 25 | SkPaint paint; |
| 26 | paint.setAntiAlias(true); |
| 27 | paint.setStyle(SkPaint::kStroke_Style); |
| 28 | paint.setStrokeWidth(5); |
| 29 | |
| 30 | SkPoint a{100, 100}; |
| 31 | SkPoint b{200, 400}; |
| 32 | SkPoint c{300, 100}; |
| 33 | |
| 34 | SkPath twoSegments; |
| 35 | twoSegments.moveTo(a); |
| 36 | twoSegments.lineTo(b); |
| 37 | twoSegments.lineTo(c); |
| 38 | |
| 39 | canvas->drawPath(twoSegments, paint); |
| 40 | |
| 41 | paint.setColor(SkColorSetARGB(255, 0, 0, 255)); |
| 42 | SkPath quadraticCurve; |
| 43 | quadraticCurve.moveTo(a); |
| 44 | quadraticCurve.quadTo(b, c); |
| 45 | canvas->drawPath(quadraticCurve, paint); |
| 46 | |
| 47 | SkFont font(nullptr, 32); |
| 48 | SkPaint textPaint; |
| 49 | textPaint.setAntiAlias(true); |
| 50 | canvas->drawString("a", a.x(), a.y(), font, textPaint); |
| 51 | canvas->drawString("b", b.x() + 20, b.y() + 20, font, textPaint); |
| 52 | canvas->drawString("c", c.x(), c.y(), font, textPaint); |
| 53 | |
| 54 | SkPaint pointPaint; |
| 55 | pointPaint.setAntiAlias(true); |
| 56 | pointPaint.setStrokeWidth(8); |
| 57 | pointPaint.setStrokeCap(SkPaint::kRound_Cap); |
| 58 | pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0)); |
| 59 | int N = 15; |
| 60 | for (int i = 0; i <= N; ++i) { |
| 61 | SkPoint p = quad(a, b, c, (float)i / N); |
| 62 | canvas->drawPoint(p.x(), p.y(), pointPaint); |
| 63 | } |
| 64 | } |
| 65 | } // END FIDDLE |