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