blob: d4471f0bcc45e47e455b1cfbd0f7d42bab8b76e0 [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_cubicTo_example_parametric_animated, 512, 512, false, 0, 3) { /* 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 * s * x0) + (3 * s * s * t * x1) + (3 * s * t * t * x2) + (t * t * t * x3) y := (s * s * s * y0) + (3 * s * s * t * y1) + (3 * s * t * t * y2) + (t * t * t * y3) */ SkPoint cubic(SkPoint p0, SkPoint p1, SkPoint p2, SkPoint p3, float t) { // a simple mathematical definition of cubic curve. // There are faster ways to calculate this. float s = 1 - t; return {(s * s * s * p0.x()) + (3 * s * s * t * p1.x()) + (3 * s * t * t * p2.x()) + (t * t * t * p3.x()), (s * s * s * p0.y()) + (3 * s * s * t * p1.y()) + (3 * s * t * t * p2.y()) + (t * t * t * p3.y())}; } static SkPoint interpolate(SkPoint a, SkPoint b, float t) { return {SkScalarInterp(a.x(), b.x(), t), SkScalarInterp(a.y(), b.y(), t)}; } void draw(SkCanvas* canvas) { canvas->clear(SkColorSetARGB(255,255,255,255)); SkPoint a{136, 64}; SkPoint b{448, 448}; SkPoint c{64, 448}; SkPoint d{376, 64}; SkPoint ab = interpolate(a, b, frame); SkPoint bc = interpolate(b, c, frame); SkPoint cd = interpolate(c, d, frame); SkPoint abc = interpolate(ab, bc, frame); SkPoint bcd = interpolate(bc, cd, frame); SkPaint paint; paint.setAntiAlias(true); paint.setStyle(SkPaint::kStroke_Style); paint.setStrokeWidth(1); canvas->drawLine(ab, bc, paint); canvas->drawLine(bc, cd, paint); canvas->drawLine(abc, bcd, paint); paint.setStrokeWidth(3); canvas->drawLine(a, b, paint); canvas->drawLine(b, c, paint); canvas->drawLine(c, d, paint); paint.setStrokeWidth(5); paint.setColor(SkColorSetARGB(255, 0, 0, 255)); SkPath cubicCurve; cubicCurve.moveTo(a); cubicCurve.cubicTo(b, c, d); canvas->drawPath(cubicCurve, paint); SkFont font(nullptr, 32); SkPaint textPaint; textPaint.setColor(SkColorSetARGB(255, 0, 255, 0)); textPaint.setAntiAlias(true); sk_sp face(fontMgr->matchFamilyStyle("DejaVu Sans Mono", SkFontStyle())); canvas->drawString("a", a.x(), a.y(), font, textPaint); canvas->drawString("b", b.x(), b.y(), font, textPaint); canvas->drawString("c", c.x()-20, c.y(), font, textPaint); canvas->drawString("d", d.x(), d.y(), font, textPaint); SkString msg = SkStringPrintf("%.4f", frame); textPaint.setColor(SkColorSetARGB(255, 204, 204, 204)); canvas->drawString(msg.c_str(), 4, 36, font, textPaint); SkPaint pointPaint; pointPaint.setAntiAlias(true); pointPaint.setStrokeWidth(8); pointPaint.setStrokeCap(SkPaint::kRound_Cap); pointPaint.setColor(SkColorSetARGB(255, 255, 0, 0)); canvas->drawPoint(interpolate(abc, bcd, frame), pointPaint); pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0)); pointPaint.setStrokeWidth(7); canvas->drawPoint(cubic(a, b, c, d, frame), pointPaint); } } // END FIDDLE