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108 lines
3.6 KiB
C++
108 lines
3.6 KiB
C++
/* Quicktex 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 <cstdint>
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#include <cstdlib>
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#include <utility>
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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 size_t Width = 4;
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static constexpr size_t Height = 4;
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static constexpr size_t SelectorSize = 6; // size of selector array in bytes
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static constexpr size_t SelectorBits = 3; // size of a selector in bits
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static constexpr size_t SelectorMax = (1 << SelectorBits) - 1; // maximum value of a selector
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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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uint8_t alpha0; // first endpoint
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uint8_t alpha1; // second endpoint
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private:
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std::array<uint8_t, SelectorSize> _selectors; // internal array of selector bytes
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public:
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// Constructors
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/// Create a new BC4Block
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constexpr BC4Block() : alpha0(0), alpha1(0), _selectors() {
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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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}
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/**
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* Create a new BC4Block
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* @param valpha0 first endpoint value
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* @param valpha1 second endpoint value
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* @param selectors the selectors as a 4x4 array of integers, between 0 and 7 inclusive.
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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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/**
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* Create a new solid BC4Block
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* @param alpha first endpoint value
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*/
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BC4Block(uint8_t alpha) {
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alpha0 = alpha;
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alpha1 = alpha;
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_selectors.fill(0);
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}
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/// Get a alpha0 and alpha1 as a pair
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AlphaPair GetAlphas() const { return AlphaPair(alpha0, alpha1); }
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/// Set alpha0 and alpha1 as a pair
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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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/// Get the block's selectors as a 4x4 array of integers between 0 and 7 inclusive.
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SelectorArray GetSelectors() const;
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/// Get the block's selectors as a 4x4 array of integers between 0 and 7 inclusive.
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void SetSelectors(const SelectorArray& unpacked);
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/// True if the block uses 6-value interpolation, i.e. alpha0 <= alpha1.
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bool Is6Value() const { return alpha0 <= alpha1; }
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/// The interpolated values of this block as an array of 8 integers.
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std::array<uint8_t, 8> GetValues() const { return Is6Value() ? GetValues6() : GetValues8(); }
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bool operator==(const BC4Block& Rhs) const;
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bool operator!=(const BC4Block& Rhs) const;
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private:
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std::array<uint8_t, 8> GetValues6() const;
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std::array<uint8_t, 8> GetValues8() const;
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};
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} // namespace quicktex::s3tc
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