59 lines
2.6 KiB
C++
59 lines
2.6 KiB
C++
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// 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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// HASH=7d3751e82d1b6ec328ffa3d6f48ca831
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REG_FIDDLE(Canvas_saveLayer_4, 256, 256, false, 3) {
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void draw(SkCanvas* canvas) {
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SkPaint pRed;
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pRed.setColor(SK_ColorRED);
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SkPaint pSolidBlue;
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pSolidBlue.setColor(SK_ColorBLUE);
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SkPaint pThirtyBlue;
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pThirtyBlue.setColor(SK_ColorBLUE);
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pThirtyBlue.setAlphaf(0.3);
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SkPaint alpha;
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alpha.setAlphaf(0.3);
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// First row: Draw two opaque red rectangles into the 0th layer. Then draw two blue
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// rectangles overlapping the red, one is solid, the other is 30% transparent.
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canvas->drawRect(SkRect::MakeLTRB(10, 10, 60, 60), pRed);
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canvas->drawRect(SkRect::MakeLTRB(150, 10, 200, 60), pRed);
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canvas->drawRect(SkRect::MakeLTRB(30, 10, 80, 60), pSolidBlue);
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canvas->drawRect(SkRect::MakeLTRB(170, 10, 220, 60), pThirtyBlue);
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// Second row: Draw two opaque red rectangles into the 0th layer. Then save a new layer;
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// when the 1st layer gets merged onto the 0th layer (i.e. when restore() is called), it will
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// use the provided paint to do so. In this case, the paint is set to have 30% opacity, but
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// it could also have things set like blend modes or image filters.
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canvas->drawRect(SkRect::MakeLTRB(10, 70, 60, 120), pRed);
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canvas->drawRect(SkRect::MakeLTRB(150, 70, 200, 120), pRed);
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canvas->saveLayer(nullptr, &alpha);
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// In the 1st layer, draw the same blue overlapping rectangles as in the first row. Notice in
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// the final output, we have two different shades of purple. The layer's alpha made the
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// opaque blue rectangle transparent, and it made the transparent blue rectangle even more so
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canvas->drawRect(SkRect::MakeLTRB(30, 70, 80, 120), pSolidBlue);
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canvas->drawRect(SkRect::MakeLTRB(170, 70, 220, 120), pThirtyBlue);
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canvas->restore();
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// Third row: save the layer first, before drawing the two red rectangle, followed by the
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// overlapping blue rectangles. Notice that the blue overwrites the red in the same way as
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// the first row because the alpha of the layer is not applied until the layer is restored.
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canvas->saveLayer(nullptr, &alpha);
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canvas->drawRect(SkRect::MakeLTRB(10, 130, 60, 180), pRed);
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canvas->drawRect(SkRect::MakeLTRB(150, 130, 200, 180), pRed);
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canvas->drawRect(SkRect::MakeLTRB(30, 130, 80, 180), pSolidBlue);
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canvas->drawRect(SkRect::MakeLTRB(170, 130, 220, 180), pThirtyBlue);
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canvas->restore();
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}
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} // END FIDDLE
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