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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 
      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