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78 lines
2.9 KiB
C++
78 lines
2.9 KiB
C++
/* Python-rgbcx Texture Compression Library
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Copyright (C) 2021 Andrew Cassidy <drewcassidy@me.com>
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Partially derived from rgbcx.h written by Richard Geldreich 2020 <richgel99@gmail.com>
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and licenced under the public domain
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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
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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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
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <cmath>
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#include <cstdint>
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#include <span>
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#include <vector>
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#include "BlockView.h"
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#include "ndebug.h"
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#include "util.h"
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namespace rgbcx {
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template <class B, size_t M, size_t N> class BlockDecoder {
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public:
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using DecodedBlock = ColorBlockView<M, N>;
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using EncodedBlock = B;
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BlockDecoder() noexcept = default;
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virtual ~BlockDecoder() noexcept = default;
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virtual void DecodeBlock(DecodedBlock dest, EncodedBlock *const block) const noexcept(ndebug) = 0;
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std::vector<Color> DecodeImage(uint8_t *bytes, unsigned image_width, unsigned image_height) {
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unsigned block_width = maximum(1U, ((image_width + 3) / 4));
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unsigned block_height = maximum(1U, ((image_height + 3) / 4));
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using Row = typename DecodedBlock::Row;
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auto image = std::vector<Color>(block_width * block_height * N * M);
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auto blocks = reinterpret_cast<B *>(bytes);
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// from experimentation, multithreading this using OpenMP actually makes decoding slower
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// due to thread creation/teardown taking longer than the decoding process itself.
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// As a result, this is left as a serial operation despite being embarassingly parallelizable
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for (unsigned y = 0; y < block_height; y++) {
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for (unsigned x = 0; x < block_width; x++) {
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unsigned pixel_x = x * N;
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unsigned pixel_y = y * M;
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assert(pixel_x >= 0);
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assert(pixel_y >= 0);
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assert(pixel_y + M <= image_height);
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assert(pixel_x + N <= image_width);
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unsigned top_left = pixel_x + (pixel_y * image_width);
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auto rows = std::array<Row *, M>();
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for (unsigned i = 0; i < M; i++) { rows[i] = reinterpret_cast<Row *>(&image[top_left + i * image_width]); }
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auto dest = DecodedBlock(&image[top_left], image_width);
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DecodeBlock(dest, &blocks[x + block_width * y]);
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}
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}
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return image;
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}
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};
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} // namespace rgbcx
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