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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 
     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
     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
     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