6c8422c671
ignore offscreen, srgb, and animated fiddles for now. Change-Id: I923131b684865698e6cda138b004930e11f504d5 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263713 Commit-Queue: Hal Canary <halcanary@google.com> Reviewed-by: Ben Wagner <bungeman@google.com>
77 lines
2.5 KiB
C++
77 lines
2.5 KiB
C++
// Copyright 2020 Google LLC.
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// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
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#include "tools/fiddle/examples.h"
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REG_FIDDLE(SkPath_cubicTo_example_parametric, 512, 512, false, 0) {
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/*
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If the starting point is (x0, y0), then this curve is defined as the
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paramentric curve as `t` goes from 0 to 1:
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s := 1 - t
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x := (s * s * s * x0) +
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(3 * s * s * t * x1) +
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(3 * s * t * t * x2) +
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(t * t * t * x3)
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y := (s * s * s * y0) +
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(3 * s * s * t * y1) +
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(3 * s * t * t * y2) +
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(t * t * t * y3)
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*/
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SkPoint cubic(SkPoint p0, SkPoint p1, SkPoint p2, SkPoint p3, float t) {
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float s = 1 - t;
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return {(s * s * s * p0.x()) + (3 * s * s * t * p1.x()) + (3 * s * t * t * p2.x()) +
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(t * t * t * p3.x()),
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(s * s * s * p0.y()) + (3 * s * s * t * p1.y()) + (3 * s * t * t * p2.y()) +
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(t * t * t * p3.y())};
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}
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void draw(SkCanvas* canvas) {
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canvas->clear(SkColorSetARGB(255, 255, 255, 255));
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SkFont font(nullptr, 32);
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SkPaint paint;
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paint.setAntiAlias(true);
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paint.setStyle(SkPaint::kStroke_Style);
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paint.setStrokeWidth(5);
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SkPoint a{136, 64};
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SkPoint b{448, 448};
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SkPoint c{64, 448};
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SkPoint d{376, 64};
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SkPath threeSegments;
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threeSegments.moveTo(a);
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threeSegments.lineTo(b);
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threeSegments.lineTo(c);
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threeSegments.lineTo(d);
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canvas->drawPath(threeSegments, paint);
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paint.setColor(SkColorSetARGB(255, 0, 0, 255));
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SkPath cubicCurve;
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cubicCurve.moveTo(a);
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cubicCurve.cubicTo(b, c, d);
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canvas->drawPath(cubicCurve, paint);
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SkPaint textPaint;
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textPaint.setColor(SkColorSetARGB(255, 0, 255, 0));
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textPaint.setAntiAlias(true);
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canvas->drawString("a", a.x(), a.y(), font, textPaint);
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canvas->drawString("b", b.x(), b.y(), font, textPaint);
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canvas->drawString("c", c.x() - 20, c.y(), font, textPaint);
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canvas->drawString("d", d.x(), d.y(), font, textPaint);
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SkPaint pointPaint;
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pointPaint.setAntiAlias(true);
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pointPaint.setStrokeWidth(8);
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pointPaint.setStrokeCap(SkPaint::kRound_Cap);
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pointPaint.setColor(SkColorSetARGB(255, 0, 255, 0));
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const int N = 16;
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for (int i = 0; i <= N; ++i) {
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SkPoint p = cubic(a, b, c, d, (float)i / N);
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canvas->drawPoint(p.x(), p.y(), pointPaint);
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}
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pointPaint.setColor(SkColorSetARGB(255, 255, 0, 0));
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}
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} // END FIDDLE
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