quicktex/quicktex/s3tc/bc4/BC4Decoder.cpp

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/* Python-rgbcx Texture Compression Library
Copyright (C) 2021 Andrew Cassidy <drewcassidy@me.com>
Partially derived from rgbcx.h written by Richard Geldreich <richgel99@gmail.com>
and licenced under the public domain
This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "BC4Decoder.h"
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#include <array> // for array
#include <cassert> // for assert
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#include "BC4Block.h"
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namespace quicktex::s3tc {
void BC4Decoder::DecodeInto(ColorBlock<4, 4> &dest, const BC4Block &block) const {
auto l = block.GetLowAlpha();
auto h = block.GetHighAlpha();
auto values = BC4Block::GetValues(l, h);
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auto selectors = block.UnpackSelectors();
for (unsigned y = 0; y < 4; y++) {
for (unsigned x = 0; x < 4; x++) {
const auto selector = selectors[y][x];
assert(selector < 8);
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auto color = dest.Get(x, y);
color[_channel] = values[selector];
dest.Set(x, y, color);
}
}
}
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ColorBlock<4, 4> BC4Decoder::DecodeBlock(const BC4Block &block) const {
auto output = ColorBlock<4, 4>();
DecodeInto(output, block);
return output;
}
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} // namespace quicktex::s3tc