aosp12/external/skia/docs/examples/shader_alphaimage.cpp

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C++

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