1 /*
2  * Copyright 2015 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #include "SkGradientShader.h"
9 #include "SkSurface.h"
10 #include "gm.h"
11 #include "sk_tool_utils.h"
12 
13 static void make_transparency(SkCanvas* canvas, SkScalar width, SkScalar height) {
14     SkPoint pts[2];
15     pts[0] = SkPoint::Make(0, 0);
16     pts[1] = SkPoint::Make(width, 0);
17     const SkColor kColors[] = {
18             SK_ColorBLACK,
19             SK_ColorGRAY,
20             SK_ColorWHITE,
21             SK_ColorRED,
22             SK_ColorYELLOW,
23             SK_ColorGREEN,
24             SK_ColorCYAN,
25             SK_ColorBLUE,
26             SK_ColorMAGENTA,
27     };
28     const SkScalar kRowHeight = height / SK_ARRAY_COUNT(kColors);
29     for (size_t i = 0; i < SK_ARRAY_COUNT(kColors); ++i) {
30         SkColor shaderColors[2];
31         shaderColors[0] = SK_AlphaTRANSPARENT;
32         shaderColors[1] = kColors[i];
33         SkPaint p;
34         p.setShader(SkGradientShader::MakeLinear(pts, shaderColors, nullptr, 2,
35                                                  SkShader::kClamp_TileMode));
36         canvas->drawRect(SkRect::MakeXYWH(0, i * kRowHeight, width, kRowHeight), p);
37     }
38 }
39 
40 // http://crrev.com/834303005
41 static sk_sp<SkShader> create_checkerboard_shader(SkColor c1, SkColor c2, int size) {
42     SkBitmap bm;
43     bm.allocN32Pixels(2 * size, 2 * size);
44     bm.eraseColor(c1);
45     bm.eraseArea(SkIRect::MakeLTRB(0, 0, size, size), c2);
46     bm.eraseArea(SkIRect::MakeLTRB(size, size, 2 * size, 2 * size), c2);
47     return SkShader::MakeBitmapShader(bm, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);
48 }
49 
50 // http://crrev.com/834303005
51 static void checkerboard(SkCanvas* canvas, SkColor c1, SkColor c2, int size) {
52     SkPaint paint;
53     paint.setShader(create_checkerboard_shader(c1, c2, size));
54     canvas->drawPaint(paint);
55 }
56 
57 /**
58  *  This GM verifies that a transparent bitmap drawn over a
59  *  checkerboard pattern looks correct.
60  */
61 DEF_SIMPLE_GM(transparency_check, canvas, 1792, 1080) {
62     checkerboard(canvas, sk_tool_utils::color_to_565(0xFF999999),
63             sk_tool_utils::color_to_565(0xFF666666), 8);
64     {
65         SkAutoCanvasRestore autoCanvasRestore(canvas, true);
66         auto surface(SkSurface::MakeRasterN32Premul(256, 9));
67         make_transparency(surface->getCanvas(), 256.0f, 9.0f);
68         canvas->scale(7.0f, 120.0f);
69         surface->draw(canvas, 0, 0, nullptr);
70     }
71 }
72