mirror of https://github.com/axmolengine/axmol.git
671 lines
21 KiB
C++
671 lines
21 KiB
C++
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// Copyright 2009 Google Inc.
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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 "etc1.h"
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#include <string.h>
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/* From http://www.khronos.org/registry/gles/extensions/OES/OES_compressed_ETC1_RGB8_texture.txt
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The number of bits that represent a 4x4 texel block is 64 bits if
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<internalformat> is given by ETC1_RGB8_OES.
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The data for a block is a number of bytes,
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{q0, q1, q2, q3, q4, q5, q6, q7}
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where byte q0 is located at the lowest memory address and q7 at
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the highest. The 64 bits specifying the block is then represented
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by the following 64 bit integer:
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int64bit = 256*(256*(256*(256*(256*(256*(256*q0+q1)+q2)+q3)+q4)+q5)+q6)+q7;
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ETC1_RGB8_OES:
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a) bit layout in bits 63 through 32 if diffbit = 0
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63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48
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-----------------------------------------------
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| base col1 | base col2 | base col1 | base col2 |
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| R1 (4bits)| R2 (4bits)| G1 (4bits)| G2 (4bits)|
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-----------------------------------------------
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47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
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---------------------------------------------------
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| base col1 | base col2 | table | table |diff|flip|
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| B1 (4bits)| B2 (4bits)| cw 1 | cw 2 |bit |bit |
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---------------------------------------------------
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b) bit layout in bits 63 through 32 if diffbit = 1
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63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48
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-----------------------------------------------
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| base col1 | dcol 2 | base col1 | dcol 2 |
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| R1' (5 bits) | dR2 | G1' (5 bits) | dG2 |
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-----------------------------------------------
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47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
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---------------------------------------------------
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| base col 1 | dcol 2 | table | table |diff|flip|
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| B1' (5 bits) | dB2 | cw 1 | cw 2 |bit |bit |
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---------------------------------------------------
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c) bit layout in bits 31 through 0 (in both cases)
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31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
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-----------------------------------------------
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| most significant pixel index bits |
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| p| o| n| m| l| k| j| i| h| g| f| e| d| c| b| a|
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-----------------------------------------------
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15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
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--------------------------------------------------
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| least significant pixel index bits |
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| p| o| n| m| l| k| j| i| h| g| f| e| d| c | b | a |
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--------------------------------------------------
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Add table 3.17.2: Intensity modifier sets for ETC1 compressed textures:
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table codeword modifier table
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------------------ ----------------------
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0 -8 -2 2 8
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1 -17 -5 5 17
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2 -29 -9 9 29
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3 -42 -13 13 42
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4 -60 -18 18 60
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5 -80 -24 24 80
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6 -106 -33 33 106
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7 -183 -47 47 183
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Add table 3.17.3 Mapping from pixel index values to modifier values for
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ETC1 compressed textures:
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pixel index value
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---------------
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msb lsb resulting modifier value
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----- ----- -------------------------
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1 1 -b (large negative value)
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1 0 -a (small negative value)
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0 0 a (small positive value)
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0 1 b (large positive value)
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*/
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static const int kModifierTable[] = {
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/* 0 */2, 8, -2, -8,
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/* 1 */5, 17, -5, -17,
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/* 2 */9, 29, -9, -29,
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/* 3 */13, 42, -13, -42,
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/* 4 */18, 60, -18, -60,
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/* 5 */24, 80, -24, -80,
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/* 6 */33, 106, -33, -106,
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/* 7 */47, 183, -47, -183 };
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static const int kLookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
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static inline etc1_byte clamp(int x) {
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return (etc1_byte) (x >= 0 ? (x < 255 ? x : 255) : 0);
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}
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static
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inline int convert4To8(int b) {
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int c = b & 0xf;
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return (c << 4) | c;
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}
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static
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inline int convert5To8(int b) {
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int c = b & 0x1f;
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return (c << 3) | (c >> 2);
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}
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static
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inline int convert6To8(int b) {
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int c = b & 0x3f;
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return (c << 2) | (c >> 4);
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}
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static
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inline int divideBy255(int d) {
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return (d + 128 + (d >> 8)) >> 8;
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}
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static
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inline int convert8To4(int b) {
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int c = b & 0xff;
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return divideBy255(c * 15);
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}
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static
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inline int convert8To5(int b) {
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int c = b & 0xff;
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return divideBy255(c * 31);
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}
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static
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inline int convertDiff(int base, int diff) {
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return convert5To8((0x1f & base) + kLookup[0x7 & diff]);
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}
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static
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void decode_subblock(etc1_byte* pOut, int r, int g, int b, const int* table,
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etc1_uint32 low, bool second, bool flipped) {
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int baseX = 0;
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int baseY = 0;
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if (second) {
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if (flipped) {
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baseY = 2;
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} else {
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baseX = 2;
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}
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}
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for (int i = 0; i < 8; i++) {
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int x, y;
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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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} 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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int k = y + (x * 4);
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int offset = ((low >> k) & 1) | ((low >> (k + 15)) & 2);
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int delta = table[offset];
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etc1_byte* q = pOut + 3 * (x + 4 * y);
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*q++ = clamp(r + delta);
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*q++ = clamp(g + delta);
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*q++ = clamp(b + delta);
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}
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}
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// Input is an ETC1 compressed version of the data.
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// Output is a 4 x 4 square of 3-byte pixels in form R, G, B
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void etc1_decode_block(const etc1_byte* pIn, etc1_byte* pOut) {
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etc1_uint32 high = (pIn[0] << 24) | (pIn[1] << 16) | (pIn[2] << 8) | pIn[3];
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etc1_uint32 low = (pIn[4] << 24) | (pIn[5] << 16) | (pIn[6] << 8) | pIn[7];
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int r1, r2, g1, g2, b1, b2;
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if (high & 2) {
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// differential
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int rBase = high >> 27;
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int gBase = high >> 19;
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int bBase = high >> 11;
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r1 = convert5To8(rBase);
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r2 = convertDiff(rBase, high >> 24);
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g1 = convert5To8(gBase);
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g2 = convertDiff(gBase, high >> 16);
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b1 = convert5To8(bBase);
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b2 = convertDiff(bBase, high >> 8);
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} else {
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// not differential
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r1 = convert4To8(high >> 28);
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r2 = convert4To8(high >> 24);
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g1 = convert4To8(high >> 20);
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g2 = convert4To8(high >> 16);
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b1 = convert4To8(high >> 12);
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b2 = convert4To8(high >> 8);
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}
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int tableIndexA = 7 & (high >> 5);
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int tableIndexB = 7 & (high >> 2);
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const int* tableA = kModifierTable + tableIndexA * 4;
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const int* tableB = kModifierTable + tableIndexB * 4;
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bool flipped = (high & 1) != 0;
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decode_subblock(pOut, r1, g1, b1, tableA, low, false, flipped);
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decode_subblock(pOut, r2, g2, b2, tableB, low, true, flipped);
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}
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typedef struct {
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etc1_uint32 high;
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etc1_uint32 low;
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etc1_uint32 score; // Lower is more accurate
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} etc_compressed;
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static
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inline void take_best(etc_compressed* a, const etc_compressed* b) {
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if (a->score > b->score) {
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*a = *b;
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}
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}
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static
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void etc_average_colors_subblock(const etc1_byte* pIn, etc1_uint32 inMask,
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etc1_byte* pColors, bool flipped, bool second) {
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int r = 0;
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int g = 0;
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int b = 0;
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if (flipped) {
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int by = 0;
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if (second) {
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by = 2;
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}
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for (int y = 0; y < 2; y++) {
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int yy = by + y;
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for (int x = 0; x < 4; x++) {
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int i = x + 4 * yy;
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if (inMask & (1 << i)) {
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const etc1_byte* p = pIn + i * 3;
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r += *(p++);
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g += *(p++);
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b += *(p++);
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}
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}
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}
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} else {
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int bx = 0;
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if (second) {
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bx = 2;
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}
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for (int y = 0; y < 4; y++) {
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for (int x = 0; x < 2; x++) {
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int xx = bx + x;
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int i = xx + 4 * y;
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if (inMask & (1 << i)) {
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const etc1_byte* p = pIn + i * 3;
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r += *(p++);
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g += *(p++);
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b += *(p++);
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}
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}
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}
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}
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pColors[0] = (etc1_byte)((r + 4) >> 3);
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pColors[1] = (etc1_byte)((g + 4) >> 3);
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pColors[2] = (etc1_byte)((b + 4) >> 3);
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}
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static
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inline int square(int x) {
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return x * x;
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}
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static etc1_uint32 chooseModifier(const etc1_byte* pBaseColors,
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const etc1_byte* pIn, etc1_uint32 *pLow, int bitIndex,
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const int* pModifierTable) {
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etc1_uint32 bestScore = ~0;
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int bestIndex = 0;
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int pixelR = pIn[0];
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int pixelG = pIn[1];
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int pixelB = pIn[2];
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int r = pBaseColors[0];
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int g = pBaseColors[1];
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int b = pBaseColors[2];
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for (int i = 0; i < 4; i++) {
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int modifier = pModifierTable[i];
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int decodedG = clamp(g + modifier);
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etc1_uint32 score = (etc1_uint32) (6 * square(decodedG - pixelG));
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if (score >= bestScore) {
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continue;
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}
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int decodedR = clamp(r + modifier);
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score += (etc1_uint32) (3 * square(decodedR - pixelR));
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if (score >= bestScore) {
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continue;
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}
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int decodedB = clamp(b + modifier);
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score += (etc1_uint32) square(decodedB - pixelB);
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if (score < bestScore) {
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bestScore = score;
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bestIndex = i;
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}
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}
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etc1_uint32 lowMask = (((bestIndex >> 1) << 16) | (bestIndex & 1))
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<< bitIndex;
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*pLow |= lowMask;
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return bestScore;
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}
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static
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void etc_encode_subblock_helper(const etc1_byte* pIn, etc1_uint32 inMask,
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etc_compressed* pCompressed, bool flipped, bool second,
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const etc1_byte* pBaseColors, const int* pModifierTable) {
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int score = pCompressed->score;
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if (flipped) {
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int by = 0;
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if (second) {
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by = 2;
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}
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for (int y = 0; y < 2; y++) {
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int yy = by + y;
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for (int x = 0; x < 4; x++) {
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int i = x + 4 * yy;
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if (inMask & (1 << i)) {
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score += chooseModifier(pBaseColors, pIn + i * 3,
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&pCompressed->low, yy + x * 4, pModifierTable);
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}
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}
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}
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} else {
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int bx = 0;
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if (second) {
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bx = 2;
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}
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for (int y = 0; y < 4; y++) {
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for (int x = 0; x < 2; x++) {
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int xx = bx + x;
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int i = xx + 4 * y;
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if (inMask & (1 << i)) {
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score += chooseModifier(pBaseColors, pIn + i * 3,
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&pCompressed->low, y + xx * 4, pModifierTable);
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}
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}
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}
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}
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|
pCompressed->score = score;
|
||
|
|
}
|
||
|
|
|
||
|
|
static bool inRange4bitSigned(int color) {
|
||
|
|
return color >= -4 && color <= 3;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void etc_encodeBaseColors(etc1_byte* pBaseColors,
|
||
|
|
const etc1_byte* pColors, etc_compressed* pCompressed) {
|
||
|
|
int r1, g1, b1, r2, g2, b2; // 8 bit base colors for sub-blocks
|
||
|
|
bool differential;
|
||
|
|
{
|
||
|
|
int r51 = convert8To5(pColors[0]);
|
||
|
|
int g51 = convert8To5(pColors[1]);
|
||
|
|
int b51 = convert8To5(pColors[2]);
|
||
|
|
int r52 = convert8To5(pColors[3]);
|
||
|
|
int g52 = convert8To5(pColors[4]);
|
||
|
|
int b52 = convert8To5(pColors[5]);
|
||
|
|
|
||
|
|
r1 = convert5To8(r51);
|
||
|
|
g1 = convert5To8(g51);
|
||
|
|
b1 = convert5To8(b51);
|
||
|
|
|
||
|
|
int dr = r52 - r51;
|
||
|
|
int dg = g52 - g51;
|
||
|
|
int db = b52 - b51;
|
||
|
|
|
||
|
|
differential = inRange4bitSigned(dr) && inRange4bitSigned(dg)
|
||
|
|
&& inRange4bitSigned(db);
|
||
|
|
if (differential) {
|
||
|
|
r2 = convert5To8(r51 + dr);
|
||
|
|
g2 = convert5To8(g51 + dg);
|
||
|
|
b2 = convert5To8(b51 + db);
|
||
|
|
pCompressed->high |= (r51 << 27) | ((7 & dr) << 24) | (g51 << 19)
|
||
|
|
| ((7 & dg) << 16) | (b51 << 11) | ((7 & db) << 8) | 2;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!differential) {
|
||
|
|
int r41 = convert8To4(pColors[0]);
|
||
|
|
int g41 = convert8To4(pColors[1]);
|
||
|
|
int b41 = convert8To4(pColors[2]);
|
||
|
|
int r42 = convert8To4(pColors[3]);
|
||
|
|
int g42 = convert8To4(pColors[4]);
|
||
|
|
int b42 = convert8To4(pColors[5]);
|
||
|
|
r1 = convert4To8(r41);
|
||
|
|
g1 = convert4To8(g41);
|
||
|
|
b1 = convert4To8(b41);
|
||
|
|
r2 = convert4To8(r42);
|
||
|
|
g2 = convert4To8(g42);
|
||
|
|
b2 = convert4To8(b42);
|
||
|
|
pCompressed->high |= (r41 << 28) | (r42 << 24) | (g41 << 20) | (g42
|
||
|
|
<< 16) | (b41 << 12) | (b42 << 8);
|
||
|
|
}
|
||
|
|
pBaseColors[0] = r1;
|
||
|
|
pBaseColors[1] = g1;
|
||
|
|
pBaseColors[2] = b1;
|
||
|
|
pBaseColors[3] = r2;
|
||
|
|
pBaseColors[4] = g2;
|
||
|
|
pBaseColors[5] = b2;
|
||
|
|
}
|
||
|
|
|
||
|
|
static
|
||
|
|
void etc_encode_block_helper(const etc1_byte* pIn, etc1_uint32 inMask,
|
||
|
|
const etc1_byte* pColors, etc_compressed* pCompressed, bool flipped) {
|
||
|
|
pCompressed->score = ~0;
|
||
|
|
pCompressed->high = (flipped ? 1 : 0);
|
||
|
|
pCompressed->low = 0;
|
||
|
|
|
||
|
|
etc1_byte pBaseColors[6];
|
||
|
|
|
||
|
|
etc_encodeBaseColors(pBaseColors, pColors, pCompressed);
|
||
|
|
|
||
|
|
int originalHigh = pCompressed->high;
|
||
|
|
|
||
|
|
const int* pModifierTable = kModifierTable;
|
||
|
|
for (int i = 0; i < 8; i++, pModifierTable += 4) {
|
||
|
|
etc_compressed temp;
|
||
|
|
temp.score = 0;
|
||
|
|
temp.high = originalHigh | (i << 5);
|
||
|
|
temp.low = 0;
|
||
|
|
etc_encode_subblock_helper(pIn, inMask, &temp, flipped, false,
|
||
|
|
pBaseColors, pModifierTable);
|
||
|
|
take_best(pCompressed, &temp);
|
||
|
|
}
|
||
|
|
pModifierTable = kModifierTable;
|
||
|
|
etc_compressed firstHalf = *pCompressed;
|
||
|
|
for (int i = 0; i < 8; i++, pModifierTable += 4) {
|
||
|
|
etc_compressed temp;
|
||
|
|
temp.score = firstHalf.score;
|
||
|
|
temp.high = firstHalf.high | (i << 2);
|
||
|
|
temp.low = firstHalf.low;
|
||
|
|
etc_encode_subblock_helper(pIn, inMask, &temp, flipped, true,
|
||
|
|
pBaseColors + 3, pModifierTable);
|
||
|
|
if (i == 0) {
|
||
|
|
*pCompressed = temp;
|
||
|
|
} else {
|
||
|
|
take_best(pCompressed, &temp);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
static void writeBigEndian(etc1_byte* pOut, etc1_uint32 d) {
|
||
|
|
pOut[0] = (etc1_byte)(d >> 24);
|
||
|
|
pOut[1] = (etc1_byte)(d >> 16);
|
||
|
|
pOut[2] = (etc1_byte)(d >> 8);
|
||
|
|
pOut[3] = (etc1_byte) d;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Input is a 4 x 4 square of 3-byte pixels in form R, G, B
|
||
|
|
// inmask is a 16-bit mask where bit (1 << (x + y * 4)) tells whether the corresponding (x,y)
|
||
|
|
// pixel is valid or not. Invalid pixel color values are ignored when compressing.
|
||
|
|
// Output is an ETC1 compressed version of the data.
|
||
|
|
|
||
|
|
void etc1_encode_block(const etc1_byte* pIn, etc1_uint32 inMask,
|
||
|
|
etc1_byte* pOut) {
|
||
|
|
etc1_byte colors[6];
|
||
|
|
etc1_byte flippedColors[6];
|
||
|
|
etc_average_colors_subblock(pIn, inMask, colors, false, false);
|
||
|
|
etc_average_colors_subblock(pIn, inMask, colors + 3, false, true);
|
||
|
|
etc_average_colors_subblock(pIn, inMask, flippedColors, true, false);
|
||
|
|
etc_average_colors_subblock(pIn, inMask, flippedColors + 3, true, true);
|
||
|
|
|
||
|
|
etc_compressed a, b;
|
||
|
|
etc_encode_block_helper(pIn, inMask, colors, &a, false);
|
||
|
|
etc_encode_block_helper(pIn, inMask, flippedColors, &b, true);
|
||
|
|
take_best(&a, &b);
|
||
|
|
writeBigEndian(pOut, a.high);
|
||
|
|
writeBigEndian(pOut + 4, a.low);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Return the size of the encoded image data (does not include size of PKM header).
|
||
|
|
|
||
|
|
etc1_uint32 etc1_get_encoded_data_size(etc1_uint32 width, etc1_uint32 height) {
|
||
|
|
return (((width + 3) & ~3) * ((height + 3) & ~3)) >> 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Encode an entire image.
|
||
|
|
// pIn - pointer to the image data. Formatted such that the Red component of
|
||
|
|
// pixel (x,y) is at pIn + pixelSize * x + stride * y + redOffset;
|
||
|
|
// pOut - pointer to encoded data. Must be large enough to store entire encoded image.
|
||
|
|
|
||
|
|
int etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 height,
|
||
|
|
etc1_uint32 pixelSize, etc1_uint32 stride, etc1_byte* pOut) {
|
||
|
|
if (pixelSize < 2 || pixelSize > 3) {
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
static const unsigned short kYMask[] = { 0x0, 0xf, 0xff, 0xfff, 0xffff };
|
||
|
|
static const unsigned short kXMask[] = { 0x0, 0x1111, 0x3333, 0x7777,
|
||
|
|
0xffff };
|
||
|
|
etc1_byte block[ETC1_DECODED_BLOCK_SIZE];
|
||
|
|
etc1_byte encoded[ETC1_ENCODED_BLOCK_SIZE];
|
||
|
|
|
||
|
|
etc1_uint32 encodedWidth = (width + 3) & ~3;
|
||
|
|
etc1_uint32 encodedHeight = (height + 3) & ~3;
|
||
|
|
|
||
|
|
for (etc1_uint32 y = 0; y < encodedHeight; y += 4) {
|
||
|
|
etc1_uint32 yEnd = height - y;
|
||
|
|
if (yEnd > 4) {
|
||
|
|
yEnd = 4;
|
||
|
|
}
|
||
|
|
int ymask = kYMask[yEnd];
|
||
|
|
for (etc1_uint32 x = 0; x < encodedWidth; x += 4) {
|
||
|
|
etc1_uint32 xEnd = width - x;
|
||
|
|
if (xEnd > 4) {
|
||
|
|
xEnd = 4;
|
||
|
|
}
|
||
|
|
int mask = ymask & kXMask[xEnd];
|
||
|
|
for (etc1_uint32 cy = 0; cy < yEnd; cy++) {
|
||
|
|
etc1_byte* q = block + (cy * 4) * 3;
|
||
|
|
const etc1_byte* p = pIn + pixelSize * x + stride * (y + cy);
|
||
|
|
if (pixelSize == 3) {
|
||
|
|
memcpy(q, p, xEnd * 3);
|
||
|
|
} else {
|
||
|
|
for (etc1_uint32 cx = 0; cx < xEnd; cx++) {
|
||
|
|
int pixel = (p[1] << 8) | p[0];
|
||
|
|
*q++ = convert5To8(pixel >> 11);
|
||
|
|
*q++ = convert6To8(pixel >> 5);
|
||
|
|
*q++ = convert5To8(pixel);
|
||
|
|
p += pixelSize;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
etc1_encode_block(block, mask, encoded);
|
||
|
|
memcpy(pOut, encoded, sizeof(encoded));
|
||
|
|
pOut += sizeof(encoded);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Decode an entire image.
|
||
|
|
// pIn - pointer to encoded data.
|
||
|
|
// pOut - pointer to the image data. Will be written such that the Red component of
|
||
|
|
// pixel (x,y) is at pIn + pixelSize * x + stride * y + redOffset. Must be
|
||
|
|
// large enough to store entire image.
|
||
|
|
|
||
|
|
|
||
|
|
int etc1_decode_image(const etc1_byte* pIn, etc1_byte* pOut,
|
||
|
|
etc1_uint32 width, etc1_uint32 height,
|
||
|
|
etc1_uint32 pixelSize, etc1_uint32 stride) {
|
||
|
|
if (pixelSize < 2 || pixelSize > 3) {
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
etc1_byte block[ETC1_DECODED_BLOCK_SIZE];
|
||
|
|
|
||
|
|
etc1_uint32 encodedWidth = (width + 3) & ~3;
|
||
|
|
etc1_uint32 encodedHeight = (height + 3) & ~3;
|
||
|
|
|
||
|
|
for (etc1_uint32 y = 0; y < encodedHeight; y += 4) {
|
||
|
|
etc1_uint32 yEnd = height - y;
|
||
|
|
if (yEnd > 4) {
|
||
|
|
yEnd = 4;
|
||
|
|
}
|
||
|
|
for (etc1_uint32 x = 0; x < encodedWidth; x += 4) {
|
||
|
|
etc1_uint32 xEnd = width - x;
|
||
|
|
if (xEnd > 4) {
|
||
|
|
xEnd = 4;
|
||
|
|
}
|
||
|
|
etc1_decode_block(pIn, block);
|
||
|
|
pIn += ETC1_ENCODED_BLOCK_SIZE;
|
||
|
|
for (etc1_uint32 cy = 0; cy < yEnd; cy++) {
|
||
|
|
const etc1_byte* q = block + (cy * 4) * 3;
|
||
|
|
etc1_byte* p = pOut + pixelSize * x + stride * (y + cy);
|
||
|
|
if (pixelSize == 3) {
|
||
|
|
memcpy(p, q, xEnd * 3);
|
||
|
|
} else {
|
||
|
|
for (etc1_uint32 cx = 0; cx < xEnd; cx++) {
|
||
|
|
etc1_byte r = *q++;
|
||
|
|
etc1_byte g = *q++;
|
||
|
|
etc1_byte b = *q++;
|
||
|
|
etc1_uint32 pixel = ((r >> 3) << 11) | ((g >> 2) << 5) | (b >> 3);
|
||
|
|
*p++ = (etc1_byte) pixel;
|
||
|
|
*p++ = (etc1_byte) (pixel >> 8);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
static const char kMagic[] = { 'P', 'K', 'M', ' ', '1', '0' };
|
||
|
|
|
||
|
|
static const etc1_uint32 ETC1_PKM_FORMAT_OFFSET = 6;
|
||
|
|
static const etc1_uint32 ETC1_PKM_ENCODED_WIDTH_OFFSET = 8;
|
||
|
|
static const etc1_uint32 ETC1_PKM_ENCODED_HEIGHT_OFFSET = 10;
|
||
|
|
static const etc1_uint32 ETC1_PKM_WIDTH_OFFSET = 12;
|
||
|
|
static const etc1_uint32 ETC1_PKM_HEIGHT_OFFSET = 14;
|
||
|
|
|
||
|
|
static const etc1_uint32 ETC1_RGB_NO_MIPMAPS = 0;
|
||
|
|
|
||
|
|
static void writeBEUint16(etc1_byte* pOut, etc1_uint32 data) {
|
||
|
|
pOut[0] = (etc1_byte) (data >> 8);
|
||
|
|
pOut[1] = (etc1_byte) data;
|
||
|
|
}
|
||
|
|
|
||
|
|
static etc1_uint32 readBEUint16(const etc1_byte* pIn) {
|
||
|
|
return (pIn[0] << 8) | pIn[1];
|
||
|
|
}
|
||
|
|
|
||
|
|
// Format a PKM header
|
||
|
|
|
||
|
|
void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height) {
|
||
|
|
memcpy(pHeader, kMagic, sizeof(kMagic));
|
||
|
|
etc1_uint32 encodedWidth = (width + 3) & ~3;
|
||
|
|
etc1_uint32 encodedHeight = (height + 3) & ~3;
|
||
|
|
writeBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET, ETC1_RGB_NO_MIPMAPS);
|
||
|
|
writeBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET, encodedWidth);
|
||
|
|
writeBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET, encodedHeight);
|
||
|
|
writeBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET, width);
|
||
|
|
writeBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET, height);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Check if a PKM header is correctly formatted.
|
||
|
|
|
||
|
|
etc1_bool etc1_pkm_is_valid(const etc1_byte* pHeader) {
|
||
|
|
if (memcmp(pHeader, kMagic, sizeof(kMagic))) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
etc1_uint32 format = readBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET);
|
||
|
|
etc1_uint32 encodedWidth = readBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET);
|
||
|
|
etc1_uint32 encodedHeight = readBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET);
|
||
|
|
etc1_uint32 width = readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
|
||
|
|
etc1_uint32 height = readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
|
||
|
|
return format == ETC1_RGB_NO_MIPMAPS &&
|
||
|
|
encodedWidth >= width && encodedWidth - width < 4 &&
|
||
|
|
encodedHeight >= height && encodedHeight - height < 4;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Read the image width from a PKM header
|
||
|
|
|
||
|
|
etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader) {
|
||
|
|
return readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Read the image height from a PKM header
|
||
|
|
|
||
|
|
etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader){
|
||
|
|
return readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
|
||
|
|
}
|