mirror of
https://github.com/RGBCube/serenity
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46 lines
903 B
C++
46 lines
903 B
C++
/*
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* Copyright (c) 2022, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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namespace Gfx::PNG {
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// https://www.w3.org/TR/PNG/#5PNG-file-signature
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static constexpr Array<u8, 8> header = { 0x89, 'P', 'N', 'G', 13, 10, 26, 10 };
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// https://www.w3.org/TR/PNG/#6Colour-values
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enum class ColorType : u8 {
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Greyscale = 0,
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Truecolor = 2, // RGB
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IndexedColor = 3,
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GreyscaleWithAlpha = 4,
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TruecolorWithAlpha = 6,
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};
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// https://www.w3.org/TR/PNG/#9Filter-types
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enum class FilterType : u8 {
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None,
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Sub,
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Up,
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Average,
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Paeth,
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};
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// https://www.w3.org/TR/PNG/#9Filter-type-4-Paeth
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ALWAYS_INLINE u8 paeth_predictor(u8 a, u8 b, u8 c)
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{
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int p = a + b - c;
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int pa = abs(p - a);
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int pb = abs(p - b);
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int pc = abs(p - c);
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if (pa <= pb && pa <= pc)
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return a;
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if (pb <= pc)
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return b;
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return c;
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}
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};
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