gm/transparency.cpp

   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 }