transparency.cpp 2.6 KB

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  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. #include "gm/gm.h"
  8. #include "include/core/SkBitmap.h"
  9. #include "include/core/SkCanvas.h"
  10. #include "include/core/SkColor.h"
  11. #include "include/core/SkPaint.h"
  12. #include "include/core/SkPoint.h"
  13. #include "include/core/SkRect.h"
  14. #include "include/core/SkRefCnt.h"
  15. #include "include/core/SkScalar.h"
  16. #include "include/core/SkShader.h"
  17. #include "include/core/SkSurface.h"
  18. #include "include/core/SkTileMode.h"
  19. #include "include/core/SkTypes.h"
  20. #include "include/effects/SkGradientShader.h"
  21. static void make_transparency(SkCanvas* canvas, SkScalar width, SkScalar height) {
  22. SkPoint pts[2];
  23. pts[0] = SkPoint::Make(0, 0);
  24. pts[1] = SkPoint::Make(width, 0);
  25. const SkColor kColors[] = {
  26. SK_ColorBLACK,
  27. SK_ColorGRAY,
  28. SK_ColorWHITE,
  29. SK_ColorRED,
  30. SK_ColorYELLOW,
  31. SK_ColorGREEN,
  32. SK_ColorCYAN,
  33. SK_ColorBLUE,
  34. SK_ColorMAGENTA,
  35. };
  36. const SkScalar kRowHeight = height / SK_ARRAY_COUNT(kColors);
  37. for (size_t i = 0; i < SK_ARRAY_COUNT(kColors); ++i) {
  38. SkColor shaderColors[2];
  39. shaderColors[0] = SK_AlphaTRANSPARENT;
  40. shaderColors[1] = kColors[i];
  41. SkPaint p;
  42. p.setShader(SkGradientShader::MakeLinear(pts, shaderColors, nullptr, 2, SkTileMode::kClamp));
  43. canvas->drawRect(SkRect::MakeXYWH(0, i * kRowHeight, width, kRowHeight), p);
  44. }
  45. }
  46. // http://crrev.com/834303005
  47. static sk_sp<SkShader> create_checkerboard_shader(SkColor c1, SkColor c2, int size) {
  48. SkBitmap bm;
  49. bm.allocN32Pixels(2 * size, 2 * size);
  50. bm.eraseColor(c1);
  51. bm.eraseArea(SkIRect::MakeLTRB(0, 0, size, size), c2);
  52. bm.eraseArea(SkIRect::MakeLTRB(size, size, 2 * size, 2 * size), c2);
  53. return bm.makeShader(SkTileMode::kRepeat, SkTileMode::kRepeat);
  54. }
  55. // http://crrev.com/834303005
  56. static void checkerboard(SkCanvas* canvas, SkColor c1, SkColor c2, int size) {
  57. SkPaint paint;
  58. paint.setShader(create_checkerboard_shader(c1, c2, size));
  59. canvas->drawPaint(paint);
  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, 0xFF999999, 0xFF666666, 8);
  67. {
  68. SkAutoCanvasRestore autoCanvasRestore(canvas, true);
  69. auto surface(SkSurface::MakeRasterN32Premul(256, 9));
  70. make_transparency(surface->getCanvas(), 256.0f, 9.0f);
  71. canvas->scale(7.0f, 120.0f);
  72. surface->draw(canvas, 0, 0, nullptr);
  73. }
  74. }