mirror of
https://github.com/drewcassidy/quicktex.git
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120 lines
4.2 KiB
C++
120 lines
4.2 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 <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 <array>
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#include <cassert>
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#include <cstdint>
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#include <cstdlib>
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#include "../../util.h"
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namespace quicktex::s3tc {
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class alignas(8) BC4Block {
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public:
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static constexpr int Width = 4;
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static constexpr int Height = 4;
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using SelectorArray = std::array<std::array<uint8_t, Width>, Height>;
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using AlphaPair = std::pair<uint8_t, uint8_t>;
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constexpr BC4Block() {
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static_assert(sizeof(BC4Block) == 8);
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static_assert(sizeof(std::array<BC4Block, 10>) == 8 * 10);
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static_assert(alignof(BC4Block) >= 8);
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alpha0 = alpha1 = 0;
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_selectors = {0, 0, 0, 0, 0, 0};
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}
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BC4Block(uint8_t valpha0, uint8_t valpha1, const SelectorArray& selectors) {
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alpha0 = valpha0;
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alpha1 = valpha1;
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SetSelectors(selectors);
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}
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constexpr AlphaPair GetAlphas() const { return AlphaPair(alpha0, alpha1); }
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void SetAlphas(AlphaPair as) {
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alpha0 = as.first;
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alpha1 = as.second;
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}
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constexpr uint64_t GetSelectorBits() const {
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auto packed = Pack<uint8_t, uint64_t, 8, SelectorSize>(_selectors);
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assert(packed <= SelectorsPackedMax);
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return packed;
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}
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void SetSelectorBits(uint64_t packed) {
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assert(packed <= SelectorsPackedMax);
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_selectors = Unpack<uint64_t, uint8_t, 8, SelectorSize>(packed);
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}
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constexpr SelectorArray GetSelectors() const {
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auto rows = Unpack<uint64_t, uint16_t, SelectorBits * Width, Height>(GetSelectorBits());
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auto unpacked = MapArray(rows, Unpack<uint16_t, uint8_t, SelectorBits, Width>);
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return unpacked;
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}
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void SetSelectors(const SelectorArray& unpacked) {
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auto rows = MapArray(unpacked, Pack<uint8_t, uint16_t, SelectorBits, Width>);
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auto packed = Pack<uint16_t, uint64_t, SelectorBits * Width, Height>(rows);
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SetSelectorBits(packed);
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}
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constexpr bool Is6Value() const { return alpha0 <= alpha1; }
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static constexpr std::array<uint8_t, 8> GetValues6(unsigned l, unsigned h) {
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return {static_cast<uint8_t>(l),
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static_cast<uint8_t>(h),
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static_cast<uint8_t>((l * 4 + h) / 5),
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static_cast<uint8_t>((l * 3 + h * 2) / 5),
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static_cast<uint8_t>((l * 2 + h * 3) / 5),
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static_cast<uint8_t>((l + h * 4) / 5),
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0,
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255};
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}
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static constexpr std::array<uint8_t, 8> GetValues8(unsigned l, unsigned h) {
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return {static_cast<uint8_t>(l),
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static_cast<uint8_t>(h),
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static_cast<uint8_t>((l * 6 + h) / 7),
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static_cast<uint8_t>((l * 5 + h * 2) / 7),
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static_cast<uint8_t>((l * 4 + h * 3) / 7),
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static_cast<uint8_t>((l * 3 + h * 4) / 7),
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static_cast<uint8_t>((l * 2 + h * 5) / 7),
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static_cast<uint8_t>((l + h * 6) / 7)};
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}
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static constexpr std::array<uint8_t, 8> GetValues(unsigned l, unsigned h) { return l > h ? GetValues8(l, h) : GetValues6(l, h); }
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static constexpr size_t SelectorSize = 6;
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static constexpr uint8_t SelectorBits = 3;
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static constexpr uint64_t SelectorsPackedMax = (1ULL << (8U * SelectorSize)) - 1U;
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uint8_t alpha0;
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uint8_t alpha1;
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private:
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std::array<uint8_t, SelectorSize> _selectors;
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};
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} // namespace quicktex::s3tc
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