skia2/docs/examples/Bitmap_extractAlpha.cpp

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// Copyright 2019 Google LLC.
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
#include "fiddle/examples.h"
// HASH=ab6577df079e6c70511cf2bfc6447b44
REG_FIDDLE(Bitmap_extractAlpha, 256, 100, false, 0) {
void draw(SkCanvas* canvas) {
SkBitmap alpha, bitmap;
bitmap.allocN32Pixels(100, 100);
SkCanvas offscreen(bitmap);
offscreen.clear(0);
SkPaint paint;
paint.setAntiAlias(true);
paint.setColor(SK_ColorBLUE);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(20);
offscreen.drawCircle(50, 50, 39, paint);
offscreen.flush();
bitmap.extractAlpha(&alpha);
paint.setColor(SK_ColorRED);
canvas->drawBitmap(bitmap, 0, 0, &paint);
canvas->drawBitmap(alpha, 100, 0, &paint);
}
} // END FIDDLE