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467 lines
18 KiB
C++
467 lines
18 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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#include "BC1Encoder.h"
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#include <array>
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#include <cassert>
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#include <climits>
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#include <cmath>
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#include <cstddef>
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#include <cstdint>
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#include <memory>
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#include <type_traits>
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#include "../BlockView.h"
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#include "../Color.h"
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#include "../Interpolator.h"
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#include "../Matrix4x4.h"
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#include "../Vector4.h"
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#include "../Vector4Int.h"
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#include "../bitwiseEnums.h"
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#include "../util.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(high);
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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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_flags = Flags::None;
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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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Color first = pixels.Get(0, 0);
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if (pixels.IsSingleColor()) {
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// single-color pixel block, do it the fast way
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EncodeBlockSingleColor(first, dest);
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return;
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}
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auto metrics = pixels.GetMetrics();
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bool needs_block_error = (_flags & Flags::UseLikelyTotalOrderings | Flags::Use3ColorBlocks | Flags::UseFullMSEEval) != Flags::None;
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needs_block_error |= (_search_rounds > 0);
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needs_block_error |= metrics.has_black && ((_flags & Flags::Use3ColorBlocksForBlackPixels) != Flags::None);
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unsigned cur_err = UINT_MAX;
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if (!needs_block_error || true) {
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// assert((_flags & Flags::TryAllInitialEndponts) == Flags::None);
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EncodeResults orig;
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FindEndpoints(pixels, _flags, metrics, orig.low, orig.high);
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FindSelectors4(pixels, orig);
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if (orig.low == orig.high) {
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EncodeBlockSingleColor(metrics.avg, dest);
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} else {
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EncodeBlock4Color(orig, dest);
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}
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}
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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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void BC1Encoder::EncodeBlock4Color(EncodeResults &block, BC1Block *dest) const {
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if (block.low == block.high) {
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EncodeBlockSingleColor(block.low.ScaleFrom565() /* Color(255, 0, 255)*/, dest);
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return;
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}
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uint8_t mask = 0;
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uint16_t low = block.low.Pack565Unscaled();
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uint16_t high = block.high.Pack565Unscaled();
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if (low < high) {
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std::swap(low, high);
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mask = 0x55;
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}
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assert(low > high);
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dest->SetLowColor(low);
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dest->SetHighColor(high);
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dest->PackSelectors(block.selectors, mask);
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}
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void encode_bc1_pick_initial(const Color *pSrc_pixels, uint32_t flags, bool grayscale_flag, int min_r, int min_g, int min_b, int max_r, int max_g, int max_b,
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int avg_r, int avg_g, int avg_b, int total_r, int total_g, int total_b, int &lr, int &lg, int &lb, int &hr, int &hg, int &hb);
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void BC1Encoder::FindEndpoints(Color4x4 pixels, BC1Encoder::Flags flags, const BC1Encoder::BlockMetrics metrics, Color &low, Color &high) const {
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int lr, lg, lb, hr, hg, hb;
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auto colors = pixels.Flatten();
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encode_bc1_pick_initial(&colors[0], 0, metrics.is_greyscale, metrics.min.r, metrics.min.g, metrics.min.b, metrics.max.r, metrics.max.g, metrics.max.b,
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metrics.avg.r, metrics.avg.g, metrics.avg.b, metrics.sums[0], metrics.sums[1], metrics.sums[2], lr, lg, lb, hr, hg, hb);
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low = Color(lr, lg, lb);
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high = Color(hr, hg, hb);
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// return;
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if (metrics.is_greyscale) {
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// specialized greyscale case
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const unsigned fr = pixels.Get(0).r;
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if (metrics.max.r - metrics.min.r < 2) {
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// single color block
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low.r = high.r = (uint8_t)scale8To5(fr);
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low.g = high.g = (uint8_t)scale8To6(fr);
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low.b = high.b = low.r;
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} else {
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low.r = low.b = scale8To5(metrics.min.r);
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low.g = scale8To6(metrics.min.r);
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high.r = high.b = scale8To5(metrics.max.r);
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high.g = scale8To6(metrics.max.r);
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}
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} else if ((flags & Flags::Use2DLS) != Flags::None) {
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// 2D Least Squares approach from Humus's example, with added inset and optimal rounding.
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Color diff = Color(metrics.max.r - metrics.min.r, metrics.max.g - metrics.min.g, metrics.max.b - metrics.min.b);
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Vector4 l = {0, 0, 0};
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Vector4 h = {0, 0, 0};
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auto &sums = metrics.sums;
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auto &min = metrics.min;
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auto &max = metrics.max;
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unsigned chan0 = (unsigned)diff.MaxChannelRGB(); // primary axis of the bounding box
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l[chan0] = (float)min[chan0];
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h[chan0] = (float)min[chan0];
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assert((diff[chan0] >= diff[(chan0 + 1) % 3]) && (diff[chan0] >= diff[(chan0 + 2) % 3]));
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std::array<unsigned, 3> sums_xy;
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for (unsigned i = 0; i < 16; i++) {
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auto val = pixels.Get(i);
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for (unsigned c = 0; c < 3; c++) { sums_xy[c] += val[chan0] * val[c]; }
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}
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auto &sum_x = sums[chan0];
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auto &sum_xx = sums_xy[chan0];
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float denominator = (float)(16 * sum_xx) - (float)(sum_x * sum_x);
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// once per secondary axis, calculate high and low using least squares
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if (fabs(denominator) > 1e-8f) {
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for (unsigned i = 1; i < 3; i++) {
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/* each secondary axis is fitted with a linear formula of the form
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* y = ax + b
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* where y is the secondary axis and x is the primary axis
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* a = (m∑xy - ∑x∑y) / m∑x² - (∑x)²
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* b = (∑x²∑y - ∑xy∑x) / m∑x² - (∑x)²
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* see Giordano/Weir pg.103 */
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const unsigned chan = (chan0 + i) % 3;
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const unsigned &sum_y = sums[chan];
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const unsigned &sum_xy = sums_xy[chan];
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float a = (float)((16 * sum_xy) - (sum_x * sum_y)) / denominator;
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float b = (float)((sum_xx * sum_y) - (sum_xy * sum_x)) / denominator;
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l[chan] = b + (a * l[chan0]);
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h[chan] = b + (a * h[chan0]);
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}
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}
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// once per axis, inset towards the center by 1/16 of the delta and scale
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for (unsigned c = 0; c < 3; c++) {
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float inset = (h[c] - l[c]) / 16.0f;
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l[c] = ((l[c] + inset) / 255.0f);
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h[c] = ((h[c] - inset) / 255.0f);
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}
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low = Color::PreciseRound565(l);
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high = Color::PreciseRound565(h);
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} else if ((flags & Flags::BoundingBox) != Flags::None) {
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// Algorithm from icbc.h compress_dxt1_fast()
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Vector4 l, h;
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const float bias = 8.0f / 255.0f;
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// rescale and inset values
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for (unsigned c = 0; c < 3; c++) { // heh, c++
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l[c] = (float)metrics.min[c] / 255.0f;
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h[c] = (float)metrics.max[c] / 255.0f;
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float inset = (h[c] - l[c] - bias) / 16.0f;
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l[c] += inset;
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h[c] -= inset;
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}
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// Select the correct diagonal across the bounding box
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int icov_xz = 0, icov_yz = 0;
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for (unsigned i = 0; i < 16; i++) {
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int b = (int)pixels.Get(i).b - metrics.avg.b;
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icov_xz += b * (int)pixels.Get(i).r - metrics.avg.r;
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icov_yz += b * (int)pixels.Get(i).g - metrics.avg.g;
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}
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if (icov_xz < 0) std::swap(l[0], h[0]);
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if (icov_yz < 0) std::swap(l[1], h[1]);
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low = Color::PreciseRound565(l);
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high = Color::PreciseRound565(h);
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} else if ((flags & Flags::BoundingBoxInt) != Flags::None) {
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// Algorithm from icbc.h compress_dxt1_fast(), but converted to integer.
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Color min, max;
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// rescale and inset values
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for (unsigned c = 0; c < 3; c++) {
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int inset = ((int)(metrics.max[c] - metrics.min[c]) - 8) >> 4; // 1/16 of delta, with bias
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min[c] = clamp255(metrics.min[c] + inset);
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max[c] = clamp255(metrics.max[c] - inset);
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}
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int icov_xz = 0, icov_yz = 0;
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for (unsigned i = 0; i < 16; i++) {
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int b = (int)pixels.Get(i).b - metrics.avg.b;
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icov_xz += b * (int)pixels.Get(i).r - metrics.avg.r;
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icov_yz += b * (int)pixels.Get(i).g - metrics.avg.g;
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}
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if (icov_xz < 0) std::swap(min.r, max.r);
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if (icov_yz < 0) std::swap(min.g, max.g);
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low = min.ScaleTo565();
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high = max.ScaleTo565();
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} else {
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// the slow way
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// Select 2 colors along the principle axis. (There must be a faster/simpler way.)
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auto min = Vector4::FromColorRGB(metrics.min);
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auto max = Vector4::FromColorRGB(metrics.max);
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auto avg = Vector4::FromColorRGB(metrics.avg);
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std::array<Vector4, 16> colors;
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Vector4 axis = {306, 601, 117}; // Luma vector
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Matrix4x4 covariance = Matrix4x4::Identity();
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const unsigned total_power_iters = (flags & Flags::Use6PowerIters) != Flags::None ? 6 : 4;
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for (unsigned i = 0; i < 16; i++) {
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colors[i] = Vector4::FromColorRGB(pixels.Get(i));
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Vector4 diff = colors[i] - avg;
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for (unsigned c1 = 0; c1 < 3; c1++) {
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for (unsigned c2 = c1; c2 < 3; c2++) {
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covariance[c1][c2] += (diff[c1] * diff[c2]);
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assert(c1 <= c2);
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}
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}
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}
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covariance /= 255.0f;
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covariance.Mirror();
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Vector4 delta = max - min;
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// realign r and g axes to match
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if (covariance[0][2] < 0) delta[0] = -delta[0]; // r vs b
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if (covariance[1][2] < 0) delta[1] = -delta[1]; // g vs b
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// using the covariance matrix, stretch the delta vector towards the primary axis of the data using power iteration
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// the end result of this may actually be the same as the least squares approach, will have to do more research
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for (unsigned power_iter = 0; power_iter < total_power_iters; power_iter++) { delta = covariance * delta; }
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// if we found any correlation, then this is our new axis. otherwise we fallback to the luma vector
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float k = delta.MaxAbs(3);
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if (k >= 2) { axis = delta * (2048.0f / k); }
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axis *= 16;
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float min_dot = INFINITY;
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float max_dot = -INFINITY;
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unsigned min_index = 0, max_index = 0;
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for (unsigned i = 0; i < 16; i++) {
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// since axis is constant here, I dont think its magnitude actually matters,
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// since we only care about the min or max dot product
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float dot = colors[i].Dot(axis);
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if (dot > max_dot) {
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max_dot = dot;
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max_index = i;
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}
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if (dot < min_dot) {
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min_dot = dot;
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min_index = i;
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}
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}
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low = pixels.Get(min_index).ScaleTo565();
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high = pixels.Get(max_index).ScaleTo565();
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}
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}
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unsigned BC1Encoder::FindSelectors4(Color4x4 pixels, BC1Encoder::EncodeResults &block, unsigned int cur_err, bool use_err) const {
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// colors in selector order, 0, 1, 2, 3
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// 0 = low color, 1 = high color, 2/3 = interpolated
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std::array<Color, 4> colors = _interpolator->InterpolateBC1(block.low, block.high, false);
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// std::array<Vector4Int, 4> colorVectors;
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// for (unsigned i = 0; i < 4; i++) { colorVectors[i] = (Vector4Int)colors[i]; }
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const std::array<uint8_t, 4> selectors = {1, 3, 2, 0};
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std::array<Vector4Int, 4> colorVectors = {(Vector4Int)colors[0], (Vector4Int)colors[2], (Vector4Int)colors[3], (Vector4Int)colors[1]};
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if (!use_err) {
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Vector4Int a = colorVectors[3] - colorVectors[0];
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Color high = block.high.ScaleFrom565();
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Color low = block.low.ScaleFrom565();
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std::array<int, 4> dots;
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for (unsigned i = 0; i < 4; i++) { dots[i] = a.Dot(colorVectors[i]); }
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int t0 = dots[0] + dots[1], t1 = dots[1] + dots[2], t2 = dots[2] + dots[3];
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a *= 2;
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for (unsigned x = 0; x < 4; x++) {
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for (unsigned y = 0; y < 4; y++) {
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int dot = a.Dot((Vector4Int)pixels.Get(x, y));
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unsigned level = (dot <= t0) + (dot < t1) + (dot < t2);
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unsigned selector = selectors[level];
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assert(level < 4);
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assert(selector < 4);
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block.selectors[y][x] = selector;
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}
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}
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return 0;
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}
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return 0;
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}
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} // namespace rgbcx
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