Add (extremely bad) BC1 encoding support
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/* 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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#include "BC1Encoder.h"
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#include <cstdint>
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#include <memory>
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#include "../BlockView.h"
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#include "../Color.h"
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#include "../bitwiseEnums.h"
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namespace rgbcx {
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using MatchList = std::array<BC1MatchEntry, 256>;
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using MatchListPtr = std::shared_ptr<MatchList>;
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using InterpolatorPtr = std::shared_ptr<Interpolator>;
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// region Free Functions/Templates
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inline void PrepSingleColorTableEntry(unsigned &error, MatchList &match_table, uint8_t v, unsigned i, uint8_t low, uint8_t high, uint8_t low8, uint8_t high8,
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bool ideal) {
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unsigned new_error = iabs(v - (int)i);
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// We only need to factor in 3% error in BC1 ideal mode.
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if (ideal) new_error += (iabs(high8 - (int)low8) * 3) / 100;
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// Favor equal endpoints, for lower error on actual GPU's which approximate the interpolation.
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if ((new_error < error) || (new_error == error && low == high)) {
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assert(new_error <= UINT8_MAX);
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match_table[i].low = (uint8_t)low;
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match_table[i].high = (uint8_t)high;
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match_table[i].error = (uint8_t)new_error;
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error = new_error;
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}
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}
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template <size_t S> void PrepSingleColorTable(MatchList &match_table, MatchList &match_table_half, Interpolator &interpolator) {
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unsigned size = 1 << S;
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assert((S == 5 && size == 32) || (S == 6 && size == 64));
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bool ideal = interpolator.IsIdeal();
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bool use_8bit = interpolator.CanInterpolate8Bit();
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for (unsigned i = 0; i < 256; i++) {
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unsigned error = 256;
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unsigned error_half = 256;
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// TODO: Can probably avoid testing for values that definitely wont yield good results,
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// e.g. low8 and high8 both much smaller or larger than index
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for (uint8_t low = 0; low < size; low++) {
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uint8_t low8 = (S == 5) ? scale5To8(low) : scale6To8(low);
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for (uint8_t high = 0; high < size; high++) {
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uint8_t high8 = (S == 5) ? scale5To8(high) : scale6To8(low);
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uint8_t value, value_half;
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if (use_8bit) {
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value = interpolator.Interpolate8(high8, low8);
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value_half = interpolator.InterpolateHalf8(high8, low8);
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} else {
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value = (S == 5) ? interpolator.Interpolate5(high, low) : interpolator.Interpolate6(high, low);
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value_half = (S == 5) ? interpolator.InterpolateHalf5(high, low) : interpolator.InterpolateHalf6(high, low);
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}
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PrepSingleColorTableEntry(error, match_table, value, i, low, high, low8, high8, ideal);
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PrepSingleColorTableEntry(error_half, match_table_half, value_half, i, low, high, low8, high8, ideal);
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}
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}
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}
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}
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// endregion
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BC1Encoder::BC1Encoder(InterpolatorPtr interpolator) : _interpolator(interpolator) {
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PrepSingleColorTable<5>(*_single_match5, *_single_match5_half, *_interpolator);
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PrepSingleColorTable<6>(*_single_match6, *_single_match6_half, *_interpolator);
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}
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void BC1Encoder::EncodeBlock(Color4x4 pixels, BC1Block *dest) const {
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auto r_view = pixels.GetChannel(0);
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auto g_view = pixels.GetChannel(1);
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auto b_view = pixels.GetChannel(2);
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if (pixels.IsSingleColor() || true) { // for now assume (wrongly) everything is a single-color block
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// single-color pixel block, do it the fast way
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EncodeBlockSingleColor(pixels.Get(0, 0), dest);
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return;
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}
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Color min, max, avg;
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pixels.GetMinMaxAvgRGB(min, max, avg);
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}
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void BC1Encoder::EncodeBlockSingleColor(Color color, BC1Block *dest) const {
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uint8_t mask = 0xAA; // 2222
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uint16_t min16, max16;
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bool using_3color = false;
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// why is there no subscript operator for shared_ptr<array>
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MatchList &match5 = *_single_match5;
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MatchList &match6 = *_single_match6;
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MatchList &match5_half = *_single_match5_half;
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MatchList &match6_half = *_single_match6_half;
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BC1MatchEntry match_r = match5[color.r];
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BC1MatchEntry match_g = match6[color.g];
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BC1MatchEntry match_b = match5[color.b];
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if ((_flags & (Flags::Use3ColorBlocks | Flags::Use3ColorBlocksForBlackPixels)) != Flags::None) {
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BC1MatchEntry match_r_half = match5_half[color.r];
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BC1MatchEntry match_g_half = match6_half[color.g];
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BC1MatchEntry match_b_half = match5_half[color.b];
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const unsigned err4 = match_r.error + match_g.error + match_b.error;
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const unsigned err3 = match_r_half.error + match_g_half.error + match_b_half.error;
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if (err3 < err4) {
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min16 = Color::Pack565Unscaled(match_r_half.low, match_g_half.low, match_b_half.low);
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max16 = Color::Pack565Unscaled(match_r_half.high, match_g_half.high, match_b_half.high);
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if (max16 > min16) std::swap(min16, max16);
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using_3color = true;
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}
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}
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if (!using_3color) {
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min16 = Color::Pack565Unscaled(match_r.low, match_g.low, match_b.low);
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max16 = Color::Pack565Unscaled(match_r.high, match_g.high, match_b.high);
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if (min16 == max16) {
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// make sure this isnt accidentally a 3-color block
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// so make max16 > min16 (l > h)
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if (min16 > 0) {
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min16--;
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mask = 0; // endpoints are equal so mask doesnt matter
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} else {
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assert(min16 == 0 && max16 == 0);
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max16 = 1;
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min16 = 0;
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mask = 0x55; // 1111 (min value only, max is ignored)
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}
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} else if (max16 < min16) {
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std::swap(min16, max16);
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mask = 0xFF; // invert mask to 3333
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}
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assert(max16 > min16);
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}
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dest->SetLowColor(max16);
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dest->SetHighColor(min16);
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dest->selectors[0] = mask;
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dest->selectors[1] = mask;
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dest->selectors[2] = mask;
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dest->selectors[3] = mask;
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}
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} // namespace rgbcx
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@ -0,0 +1,145 @@
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/* 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 <mutex>
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#include "../BlockEncoder.h"
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#include "../BlockView.h"
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#include "../Interpolator.h"
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#include "../bitwiseEnums.h"
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#include "../ndebug.h"
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#include "../tables.h"
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#include "BC1Block.h"
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namespace rgbcx {
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struct BC1MatchEntry {
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uint8_t high;
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uint8_t low;
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uint8_t error;
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};
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class BC1Encoder : public BlockEncoder<BC1Block, 4, 4> {
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public:
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using InterpolatorPtr = std::shared_ptr<Interpolator>;
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enum class Flags : uint32_t {
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None = 0,
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// Try to improve quality using the most likely total orderings.
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// The total_orderings_to_try parameter will then control the number of total orderings to try for 4 color blocks, and the
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// total_orderings_to_try3 parameter will control the number of total orderings to try for 3 color blocks (if they are enabled).
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UseLikelyTotalOrderings = 2,
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// Use 2 least squares pass, instead of one (same as stb_dxt's HIGHQUAL option).
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// Recommended if you're enabling UseLikelyTotalOrderings.
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TwoLeastSquaresPasses = 4,
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// Use3ColorBlocksForBlackPixels allows the BC1 encoder to use 3-color blocks for blocks containing black or very dark pixels.
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// You shader/engine MUST ignore the alpha channel on textures encoded with this flag.
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// Average quality goes up substantially for my 100 texture corpus (~.5 dB), so it's worth using if you can.
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// Note the BC1 encoder does not actually support transparency in 3-color mode.
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// Don't set when encoding to BC3.
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Use3ColorBlocksForBlackPixels = 8,
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// If Use3ColorBlocks is set, the encoder can use 3-color mode for a small but noticeable gain in average quality, but lower perf.
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// If you also specify the UseLikelyTotalOrderings flag, set the total_orderings_to_try3 paramter to the number of total orderings to try.
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// Don't set when encoding to BC3.
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Use3ColorBlocks = 16,
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// Iterative will greatly increase encode time, but is very slightly higher quality.
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// Same as squish's iterative cluster fit option. Not really worth the tiny boost in quality, unless you just don't care about perf. at all.
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Iterative = 32,
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// BoundingBox enables a fast all-integer PCA approximation on 4-color blocks.
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// At level 0 options (no other flags), this is ~15% faster, and higher *average* quality.
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BoundingBox = 64,
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// Use a slightly lower quality, but ~30% faster MSE evaluation function for 4-color blocks.
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UseFasterMSEEval = 128,
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// Examine all colors to compute selectors/MSE (slower than default)
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UseFullMSEEval = 256,
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// Use 2D least squares+inset+optimal rounding (the method used in Humus's GPU texture encoding demo), instead of PCA.
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// Around 18% faster, very slightly lower average quality to better (depends on the content).
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Use2DLS = 512,
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// Use 6 power iterations vs. 4 for PCA.
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Use6PowerIters = 2048,
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// Check all total orderings - *very* slow. The encoder is not designed to be used in this way.
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Exhaustive = 8192,
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// Try 2 different ways of choosing the initial endpoints.
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TryAllInitialEndponts = 16384,
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// Same as BoundingBox, but implemented using integer math (faster, slightly less quality)
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BoundingBoxInt = 32768,
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// Try refining the final endpoints by examining nearby colors.
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EndpointSearchRoundsShift = 22,
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EndpointSearchRoundsMask = 1023U << EndpointSearchRoundsShift,
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};
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BC1Encoder(InterpolatorPtr interpolator);
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void EncodeBlock(Color4x4 pixels, BC1Block *dest) const override;
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private:
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const InterpolatorPtr _interpolator;
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Flags _flags;
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unsigned _search_rounds;
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unsigned _orderings4;
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unsigned _orderings3;
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void EncodeBlockSingleColor(Color color, BC1Block *dest) const;
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// match tables used for single-color blocks
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// Each entry includes a high and low pair that best reproduces the 8-bit index as well as possible,
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// with an included error value
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// these depend on the interpolator
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using MatchList = std::array<BC1MatchEntry, 256>;
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using MatchListPtr = std::shared_ptr<MatchList>;
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const MatchListPtr _single_match5 = std::make_shared<MatchList>();
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const MatchListPtr _single_match6 = std::make_shared<MatchList>();
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const MatchListPtr _single_match5_half = std::make_shared<MatchList>();
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const MatchListPtr _single_match6_half = std::make_shared<MatchList>();
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// static lookup tables, generated the first time an encoder is created
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// the mutex prevents race conditions if two encoders are created on different threads
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static std::mutex _luts_mutex;
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static bool _luts_initialized;
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// lookup table for hash values
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static uint16_t g_total_ordering4_hash[4096];
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static uint16_t g_total_ordering3_hash[256];
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static float g_selector_factors4[NUM_UNIQUE_TOTAL_ORDERINGS4][3];
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static float g_selector_factors3[NUM_UNIQUE_TOTAL_ORDERINGS3][3];
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};
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} // namespace rgbcx
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