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 // 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(SkPath_quadTo_example_parametric, 512, 512, false, 0) { 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) */ 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{100, 100}; SkPoint b{200, 400}; SkPoint c{300, 100}; SkPath twoSegments; twoSegments.moveTo(a); twoSegments.lineTo(b); twoSegments.lineTo(c); canvas->drawPath(twoSegments, paint); paint.setColor(SkColorSetARGB(255, 0, 0, 255)); SkPath quadraticCurve; quadraticCurve.moveTo(a); quadraticCurve.quadTo(b, c); canvas->drawPath(quadraticCurve, paint); SkFont font(nullptr, 32); SkPaint textPaint; 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)); int N = 15; for (int i = 0; i <= N; ++i) { SkPoint p = quad(a, b, c, (float)i / N); canvas->drawPoint(p.x(), p.y(), pointPaint); } } } // END FIDDLE