submodule/skia/docs/examples/shader_alphaimage.cpp

   1 // Copyright 2020 Google LLC.
   2 // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
   3 #include "tools/fiddle/examples.h"
   4 REG_FIDDLE(shader_alphaimage, 256, 256, false, 0) {
   5 sk_sp<SkImage> alpha_image() {
   6     auto s = SkSurface::MakeRaster(SkImageInfo::MakeA8(128, 128));
   7     s->getCanvas()->clear(SkColorSetARGB(0xF0, 0x00, 0x00, 0x00));
   8     return s->makeImageSnapshot();
   9 }
  10 sk_sp<SkShader> linear_gradient() {
  11     SkPoint gpts[2] = {{0, 0}, {256, 256}};
  12     SkColor gc[6] = {SK_ColorCYAN, SK_ColorBLUE,   SK_ColorMAGENTA,
  13                      SK_ColorRED,  SK_ColorYELLOW, SK_ColorGREEN};
  14     return SkGradientShader::MakeLinear(gpts, gc, nullptr, 6, SkTileMode::kClamp);
  15 }
  16
  17 void draw(SkCanvas* canvas) {
  18     canvas->clear(SK_ColorLTGRAY);
  19     SkPaint p;
  20     p.setShader(linear_gradient());
  21     auto i = alpha_image();
  22     canvas->drawImage(i.get(), 128, 0, SkSamplingOptions(), &p);
  23     canvas->drawRect({0, 128, 128, 256}, p);
  24 }
  25 }  // END FIDDLE