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 
make_transparency(SkCanvas * canvas,SkScalar width,SkScalar height)12 static void make_transparency(SkCanvas* canvas,
13                               SkScalar width,
14                               SkScalar height) {
15     SkPoint pts[2];
16     pts[0] = SkPoint::Make(0, 0);
17     pts[1] = SkPoint::Make(width, 0);
18     const SkColor kColors[] = {
19             SK_ColorBLACK,
20             SK_ColorGRAY,
21             SK_ColorWHITE,
22             SK_ColorRED,
23             SK_ColorYELLOW,
24             SK_ColorGREEN,
25             SK_ColorCYAN,
26             SK_ColorBLUE,
27             SK_ColorMAGENTA,
28     };
29     const SkScalar kRowHeight = height / SK_ARRAY_COUNT(kColors);
30     for (size_t i = 0; i < SK_ARRAY_COUNT(kColors); ++i) {
31         SkColor shaderColors[2];
32         shaderColors[0] = SK_AlphaTRANSPARENT;
33         shaderColors[1] = kColors[i];
34         SkAutoTUnref<SkShader> shader(SkGradientShader::CreateLinear(
35                 pts, shaderColors, nullptr, 2, SkShader::kClamp_TileMode));
36         SkRect r = SkRect::MakeXYWH(0, i * kRowHeight, width, kRowHeight);
37         SkPaint p;
38         p.setShader(shader);
39         canvas->drawRect(r, p);
40     }
41 }
42 
43 // http://crrev.com/834303005
create_checkerboard_shader(SkColor c1,SkColor c2,int size)44 static SkShader* create_checkerboard_shader(SkColor c1, SkColor c2, int size) {
45     SkBitmap bm;
46     bm.allocN32Pixels(2 * size, 2 * size);
47     bm.eraseColor(c1);
48     bm.eraseArea(SkIRect::MakeLTRB(0, 0, size, size), c2);
49     bm.eraseArea(SkIRect::MakeLTRB(size, size, 2 * size, 2 * size), c2);
50     return SkShader::CreateBitmapShader(bm, SkShader::kRepeat_TileMode,
51                                         SkShader::kRepeat_TileMode);
52 }
53 
54 // http://crrev.com/834303005
checkerboard(SkCanvas * canvas,SkColor c1,SkColor c2,int size)55 static void checkerboard(SkCanvas* canvas, SkColor c1, SkColor c2, int size) {
56     SkPaint paint;
57     paint.setShader(create_checkerboard_shader(c1, c2, size))->unref();
58     canvas->drawPaint(paint);
59 }
60 
61 /**
62  *  This GM verifies that a transparent bitmap drawn over a
63  *  checkerboard pattern looks correct.
64  */
65 DEF_SIMPLE_GM(transparency_check, canvas, 1792, 1080) {
66     checkerboard(canvas, sk_tool_utils::color_to_565(0xFF999999),
67             sk_tool_utils::color_to_565(0xFF666666), 8);
68     {
69         SkAutoCanvasRestore autoCanvasRestore(canvas, true);
70         SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(256, 9));
71         make_transparency(surface->getCanvas(), 256.0f, 9.0f);
72         canvas->scale(7.0f, 120.0f);
73         surface->draw(canvas, 0, 0, nullptr);
74     }
75 }
76