1 // Copyright 2020 Google LLC.
2 // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
3 #include "tools/fiddle/examples.h"
4 // HASH=7d3751e82d1b6ec328ffa3d6f48ca831
5 REG_FIDDLE(Canvas_saveLayer_4, 256, 256, false, 3) {
draw(SkCanvas * canvas)6 void draw(SkCanvas* canvas) {
7 SkPaint pRed;
8 pRed.setColor(SK_ColorRED);
9
10 SkPaint pSolidBlue;
11 pSolidBlue.setColor(SK_ColorBLUE);
12
13 SkPaint pThirtyBlue;
14 pThirtyBlue.setColor(SK_ColorBLUE);
15 pThirtyBlue.setAlphaf(0.3);
16
17 SkPaint alpha;
18 alpha.setAlphaf(0.3);
19
20 // First row: Draw two opaque red rectangles into the 0th layer. Then draw two blue
21 // rectangles overlapping the red, one is solid, the other is 30% transparent.
22 canvas->drawRect(SkRect::MakeLTRB(10, 10, 60, 60), pRed);
23 canvas->drawRect(SkRect::MakeLTRB(150, 10, 200, 60), pRed);
24
25 canvas->drawRect(SkRect::MakeLTRB(30, 10, 80, 60), pSolidBlue);
26 canvas->drawRect(SkRect::MakeLTRB(170, 10, 220, 60), pThirtyBlue);
27
28 // Second row: Draw two opaque red rectangles into the 0th layer. Then save a new layer;
29 // when the 1st layer gets merged onto the 0th layer (i.e. when restore() is called), it will
30 // use the provided paint to do so. In this case, the paint is set to have 30% opacity, but
31 // it could also have things set like blend modes or image filters.
32 canvas->drawRect(SkRect::MakeLTRB(10, 70, 60, 120), pRed);
33 canvas->drawRect(SkRect::MakeLTRB(150, 70, 200, 120), pRed);
34
35 canvas->saveLayer(nullptr, &alpha);
36
37 // In the 1st layer, draw the same blue overlapping rectangles as in the first row. Notice in
38 // the final output, we have two different shades of purple. The layer's alpha made the
39 // opaque blue rectangle transparent, and it made the transparent blue rectangle even more so
40 canvas->drawRect(SkRect::MakeLTRB(30, 70, 80, 120), pSolidBlue);
41 canvas->drawRect(SkRect::MakeLTRB(170, 70, 220, 120), pThirtyBlue);
42
43 canvas->restore();
44
45 // Third row: save the layer first, before drawing the two red rectangle, followed by the
46 // overlapping blue rectangles. Notice that the blue overwrites the red in the same way as
47 // the first row because the alpha of the layer is not applied until the layer is restored.
48 canvas->saveLayer(nullptr, &alpha);
49
50 canvas->drawRect(SkRect::MakeLTRB(10, 130, 60, 180), pRed);
51 canvas->drawRect(SkRect::MakeLTRB(150, 130, 200, 180), pRed);
52
53 canvas->drawRect(SkRect::MakeLTRB(30, 130, 80, 180), pSolidBlue);
54 canvas->drawRect(SkRect::MakeLTRB(170, 130, 220, 180), pThirtyBlue);
55
56 canvas->restore();
57 }
58 } // END FIDDLE
59