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third_party
skia
docs
examples
Canvas_saveLayer_4.cpp
Go to the documentation of this file.
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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
SK_ColorBLUE
constexpr SkColor SK_ColorBLUE
Definition
SkColor.h:135
SK_ColorRED
constexpr SkColor SK_ColorRED
Definition
SkColor.h:126
draw
static void draw(SkCanvas *canvas, SkRect &target, int x, int y)
Definition
aaclip.cpp:27
SkCanvas
Definition
SkCanvas.h:106
SkCanvas::saveLayer
int saveLayer(const SkRect *bounds, const SkPaint *paint)
Definition
SkCanvas.cpp:500
SkCanvas::drawRect
void drawRect(const SkRect &rect, const SkPaint &paint)
Definition
SkCanvas.cpp:1997
SkCanvas::restore
void restore()
Definition
SkCanvas.cpp:465
SkPaint
Definition
SkPaint.h:44
SkPaint::setColor
void setColor(SkColor color)
Definition
SkPaint.cpp:119
SkPaint::setAlphaf
void setAlphaf(float a)
Definition
SkPaint.cpp:130
examples.h
REG_FIDDLE
#define REG_FIDDLE(NAME, W, H, TEXT, I)
Definition
examples.h:60
SkRect::MakeLTRB
static constexpr SkRect MakeLTRB(float l, float t, float r, float b)
Definition
SkRect.h:646
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