115 lines
3.3 KiB
C
115 lines
3.3 KiB
C
// Copyright 2009 Google Inc.
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//
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// Based on the code from Android ETC1Util.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "etclib.h"
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static void ETC_DecodeETC1SubBlock( byte *out, qboolean outRGBA, int r, int g, int b, int tableIndex, unsigned int low, qboolean second, qboolean flipped ){
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int baseX = 0, baseY = 0;
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const int modifierTable[] = {
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2, 8, -2, -8,
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5, 17, -5, -17,
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9, 29, -9, -29,
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13, 42, -13, -42,
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18, 60, -18, -60,
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24, 80, -24, -80,
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33, 106, -33, -106,
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47, 183, -47, -183
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};
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const int *table = modifierTable + tableIndex * 4;
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int i;
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if ( second ) {
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if ( flipped ) {
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baseY = 2;
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}
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else {
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baseX = 2;
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}
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}
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for ( i = 0; i < 8; i++ )
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{
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int x, y, k, delta;
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int qr, qg, qb;
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byte *q;
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if ( flipped ) {
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x = baseX + ( i >> 1 );
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y = baseY + ( i & 1 );
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}
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else {
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x = baseX + ( i >> 2 );
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y = baseY + ( i & 3 );
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}
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k = y + ( x * 4 );
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delta = table[( ( low >> k ) & 1 ) | ( ( low >> ( k + 15 ) ) & 2 )];
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qr = r + delta;
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qg = g + delta;
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qb = b + delta;
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if ( outRGBA ) {
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q = out + 4 * ( x + 4 * y );
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}
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else {
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q = out + 3 * ( x + 4 * y );
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}
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*( q++ ) = ( ( qr > 0 ) ? ( ( qr < 255 ) ? qr : 255 ) : 0 );
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*( q++ ) = ( ( qg > 0 ) ? ( ( qg < 255 ) ? qg : 255 ) : 0 );
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*( q++ ) = ( ( qb > 0 ) ? ( ( qb < 255 ) ? qb : 255 ) : 0 );
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if ( outRGBA ) {
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*( q++ ) = 255;
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}
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}
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}
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void ETC_DecodeETC1Block( const byte* in, byte* out, qboolean outRGBA ){
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unsigned int high = ( in[0] << 24 ) | ( in[1] << 16 ) | ( in[2] << 8 ) | in[3];
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unsigned int low = ( in[4] << 24 ) | ( in[5] << 16 ) | ( in[6] << 8 ) | in[7];
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int r1, r2, g1, g2, b1, b2;
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qboolean flipped = ( ( high & 1 ) != 0 );
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if ( high & 2 ) {
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int rBase, gBase, bBase;
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const int lookup[] = { 0, 1, 2, 3, -4, -3, -2, -1 };
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rBase = ( high >> 27 ) & 31;
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r1 = ( rBase << 3 ) | ( rBase >> 2 );
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rBase = ( rBase + ( lookup[( high >> 24 ) & 7] ) ) & 31;
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r2 = ( rBase << 3 ) | ( rBase >> 2 );
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gBase = ( high >> 19 ) & 31;
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g1 = ( gBase << 3 ) | ( gBase >> 2 );
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gBase = ( gBase + ( lookup[( high >> 16 ) & 7] ) ) & 31;
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g2 = ( gBase << 3 ) | ( gBase >> 2 );
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bBase = ( high >> 11 ) & 31;
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b1 = ( bBase << 3 ) | ( bBase >> 2 );
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bBase = ( bBase + ( lookup[( high >> 8 ) & 7] ) ) & 31;
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b2 = ( bBase << 3 ) | ( bBase >> 2 );
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}
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else {
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r1 = ( ( high >> 24 ) & 0xf0 ) | ( ( high >> 28 ) & 0xf );
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r2 = ( ( high >> 20 ) & 0xf0 ) | ( ( high >> 24 ) & 0xf );
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g1 = ( ( high >> 16 ) & 0xf0 ) | ( ( high >> 20 ) & 0xf );
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g2 = ( ( high >> 12 ) & 0xf0 ) | ( ( high >> 16 ) & 0xf );
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b1 = ( ( high >> 8 ) & 0xf0 ) | ( ( high >> 12 ) & 0xf );
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b2 = ( ( high >> 4 ) & 0xf0 ) | ( ( high >> 8 ) & 0xf );
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}
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ETC_DecodeETC1SubBlock( out, outRGBA, r1, g1, b1, ( high >> 5 ) & 7, low, qfalse, flipped );
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ETC_DecodeETC1SubBlock( out, outRGBA, r2, g2, b2, ( high >> 2 ) & 7, low, qtrue, flipped );
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}
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