skia2/docs/examples/UnpremulBugs.cpp

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// 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(UnpremulBugs, 400, 400, false, 6) {
void fill(SkBitmap & b, SkColor c, int n) {
for (int y = 0; y < n; y++) {
for (int x = 0; x < n; x++) {
*(b.getAddr32(x, y)) = c;
}
}
}
void doCell(SkCanvas* canvas, float x, float y, SkAlphaType at, SkColor c, int n) {
SkImageInfo info = SkImageInfo::MakeS32(n, n, at);
SkBitmap bmp;
bmp.allocPixels(info);
fill(bmp, c, n);
sk_sp<SkImage> img = SkImage::MakeFromBitmap(bmp);
SkPaint paint;
const SkTileMode tile = SkTileMode::kRepeat;
paint.setShader(img->makeShader(tile, tile, nullptr));
canvas->drawRect(SkRect::MakeXYWH(x, y, 50, 50), paint);
}
void draw(SkCanvas* canvas) {
canvas->clear(SK_ColorBLACK);
doCell(canvas, 0, 0, kPremul_SkAlphaType, 0x80404040, 2);
doCell(canvas, 0, 50, kUnpremul_SkAlphaType, 0x80808080, 2);
doCell(canvas, 50, 0, kPremul_SkAlphaType, 0x80808080, 2);
doCell(canvas, 50, 50, kUnpremul_SkAlphaType, 0x80FFFFFF, 2);
doCell(canvas, 110, 0, kPremul_SkAlphaType, 0x80404040, 1);
doCell(canvas, 110, 50, kUnpremul_SkAlphaType, 0x80808080, 1);
doCell(canvas, 160, 0, kPremul_SkAlphaType, 0x80808080, 1);
doCell(canvas, 160, 50, kUnpremul_SkAlphaType, 0x80FFFFFF, 1);
SkFont font(nullptr, 12);
SkPaint paint;
paint.setColor(SK_ColorWHITE);
canvas->drawString("Premul", 220, 20, font, paint);
canvas->drawString("Unpremul", 220, 70, font, paint);
canvas->drawString("Gray", 5, 120, font, paint);
canvas->drawString("White", 55, 120, font, paint);
canvas->drawString("Gray", 115, 120, font, paint);
canvas->drawString("White", 165, 120, font, paint);
canvas->drawString("2x2", 40, 150, font, paint);
canvas->drawString("1x1", 150, 150, font, paint);
}
} // END FIDDLE