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  1. /*
  2.  * Texture block compression
  3.  * Copyright (C) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>
  4.  * Based on public domain code by Fabian Giesen, Sean Barrett and Yann Collet.
  5.  *
  6.  * This file is part of FFmpeg
  7.  *
  8.  * Permission is hereby granted, free of charge, to any person obtaining a
  9.  * copy of this software and associated documentation files (the "Software"),
  10.  * to deal in the Software without restriction, including without limitation
  11.  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12.  * and/or sell copies of the Software, and to permit persons to whom the
  13.  * Software is furnished to do so, subject to the following conditions:
  14.  * The above copyright notice and this permission notice shall be included
  15.  * in all copies or substantial portions of the Software.
  16.  *
  17.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18.  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19.  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20.  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21.  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22.  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  23.  * IN THE SOFTWARE.
  24.  */
  25.  
  26. #include <stddef.h>
  27. #include <stdint.h>
  28.  
  29. #include "libavutil/attributes.h"
  30. #include "libavutil/common.h"
  31. #include "libavutil/intreadwrite.h"
  32.  
  33. #include "texturedsp.h"
  34.  
  35. const static uint8_t expand5[32] = {
  36.       0,   8,  16,  24,  33,  41,  49,  57,  66,  74,  82,  90,
  37.      99, 107, 115, 123, 132, 140, 148, 156, 165, 173, 181, 189,
  38.     198, 206, 214, 222, 231, 239, 247, 255,
  39. };
  40.  
  41. const static uint8_t expand6[64] = {
  42.       0,   4,   8,  12,  16,  20,  24,  28,  32,  36,  40,  44,
  43.      48,  52,  56,  60,  65,  69,  73,  77,  81,  85,  89,  93,
  44.      97, 101, 105, 109, 113, 117, 121, 125, 130, 134, 138, 142,
  45.     146, 150, 154, 158, 162, 166, 170, 174, 178, 182, 186, 190,
  46.     195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239,
  47.     243, 247, 251, 255,
  48. };
  49.  
  50. const static uint8_t match5[256][2] = {
  51.     {  0,  0 }, {  0,  0 }, {  0,  1 }, {  0,  1 }, {  1,  0 }, {  1,  0 },
  52.     {  1,  0 }, {  1,  1 }, {  1,  1 }, {  2,  0 }, {  2,  0 }, {  0,  4 },
  53.     {  2,  1 }, {  2,  1 }, {  2,  1 }, {  3,  0 }, {  3,  0 }, {  3,  0 },
  54.     {  3,  1 }, {  1,  5 }, {  3,  2 }, {  3,  2 }, {  4,  0 }, {  4,  0 },
  55.     {  4,  1 }, {  4,  1 }, {  4,  2 }, {  4,  2 }, {  4,  2 }, {  3,  5 },
  56.     {  5,  1 }, {  5,  1 }, {  5,  2 }, {  4,  4 }, {  5,  3 }, {  5,  3 },
  57.     {  5,  3 }, {  6,  2 }, {  6,  2 }, {  6,  2 }, {  6,  3 }, {  5,  5 },
  58.     {  6,  4 }, {  6,  4 }, {  4,  8 }, {  7,  3 }, {  7,  3 }, {  7,  3 },
  59.     {  7,  4 }, {  7,  4 }, {  7,  4 }, {  7,  5 }, {  5,  9 }, {  7,  6 },
  60.     {  7,  6 }, {  8,  4 }, {  8,  4 }, {  8,  5 }, {  8,  5 }, {  8,  6 },
  61.     {  8,  6 }, {  8,  6 }, {  7,  9 }, {  9,  5 }, {  9,  5 }, {  9,  6 },
  62.     {  8,  8 }, {  9,  7 }, {  9,  7 }, {  9,  7 }, { 10,  6 }, { 10,  6 },
  63.     { 10,  6 }, { 10,  7 }, {  9,  9 }, { 10,  8 }, { 10,  8 }, {  8, 12 },
  64.     { 11,  7 }, { 11,  7 }, { 11,  7 }, { 11,  8 }, { 11,  8 }, { 11,  8 },
  65.     { 11,  9 }, {  9, 13 }, { 11, 10 }, { 11, 10 }, { 12,  8 }, { 12,  8 },
  66.     { 12,  9 }, { 12,  9 }, { 12, 10 }, { 12, 10 }, { 12, 10 }, { 11, 13 },
  67.     { 13,  9 }, { 13,  9 }, { 13, 10 }, { 12, 12 }, { 13, 11 }, { 13, 11 },
  68.     { 13, 11 }, { 14, 10 }, { 14, 10 }, { 14, 10 }, { 14, 11 }, { 13, 13 },
  69.     { 14, 12 }, { 14, 12 }, { 12, 16 }, { 15, 11 }, { 15, 11 }, { 15, 11 },
  70.     { 15, 12 }, { 15, 12 }, { 15, 12 }, { 15, 13 }, { 13, 17 }, { 15, 14 },
  71.     { 15, 14 }, { 16, 12 }, { 16, 12 }, { 16, 13 }, { 16, 13 }, { 16, 14 },
  72.     { 16, 14 }, { 16, 14 }, { 15, 17 }, { 17, 13 }, { 17, 13 }, { 17, 14 },
  73.     { 16, 16 }, { 17, 15 }, { 17, 15 }, { 17, 15 }, { 18, 14 }, { 18, 14 },
  74.     { 18, 14 }, { 18, 15 }, { 17, 17 }, { 18, 16 }, { 18, 16 }, { 16, 20 },
  75.     { 19, 15 }, { 19, 15 }, { 19, 15 }, { 19, 16 }, { 19, 16 }, { 19, 16 },
  76.     { 19, 17 }, { 17, 21 }, { 19, 18 }, { 19, 18 }, { 20, 16 }, { 20, 16 },
  77.     { 20, 17 }, { 20, 17 }, { 20, 18 }, { 20, 18 }, { 20, 18 }, { 19, 21 },
  78.     { 21, 17 }, { 21, 17 }, { 21, 18 }, { 20, 20 }, { 21, 19 }, { 21, 19 },
  79.     { 21, 19 }, { 22, 18 }, { 22, 18 }, { 22, 18 }, { 22, 19 }, { 21, 21 },
  80.     { 22, 20 }, { 22, 20 }, { 20, 24 }, { 23, 19 }, { 23, 19 }, { 23, 19 },
  81.     { 23, 20 }, { 23, 20 }, { 23, 20 }, { 23, 21 }, { 21, 25 }, { 23, 22 },
  82.     { 23, 22 }, { 24, 20 }, { 24, 20 }, { 24, 21 }, { 24, 21 }, { 24, 22 },
  83.     { 24, 22 }, { 24, 22 }, { 23, 25 }, { 25, 21 }, { 25, 21 }, { 25, 22 },
  84.     { 24, 24 }, { 25, 23 }, { 25, 23 }, { 25, 23 }, { 26, 22 }, { 26, 22 },
  85.     { 26, 22 }, { 26, 23 }, { 25, 25 }, { 26, 24 }, { 26, 24 }, { 24, 28 },
  86.     { 27, 23 }, { 27, 23 }, { 27, 23 }, { 27, 24 }, { 27, 24 }, { 27, 24 },
  87.     { 27, 25 }, { 25, 29 }, { 27, 26 }, { 27, 26 }, { 28, 24 }, { 28, 24 },
  88.     { 28, 25 }, { 28, 25 }, { 28, 26 }, { 28, 26 }, { 28, 26 }, { 27, 29 },
  89.     { 29, 25 }, { 29, 25 }, { 29, 26 }, { 28, 28 }, { 29, 27 }, { 29, 27 },
  90.     { 29, 27 }, { 30, 26 }, { 30, 26 }, { 30, 26 }, { 30, 27 }, { 29, 29 },
  91.     { 30, 28 }, { 30, 28 }, { 30, 28 }, { 31, 27 }, { 31, 27 }, { 31, 27 },
  92.     { 31, 28 }, { 31, 28 }, { 31, 28 }, { 31, 29 }, { 31, 29 }, { 31, 30 },
  93.     { 31, 30 }, { 31, 30 }, { 31, 31 }, { 31, 31 },
  94. };
  95.  
  96. const static uint8_t match6[256][2] = {
  97.     {  0,  0 }, {  0,  1 }, {  1,  0 }, {  1,  0 }, {  1,  1 }, {  2,  0 },
  98.     {  2,  1 }, {  3,  0 }, {  3,  0 }, {  3,  1 }, {  4,  0 }, {  4,  0 },
  99.     {  4,  1 }, {  5,  0 }, {  5,  1 }, {  6,  0 }, {  6,  0 }, {  6,  1 },
  100.     {  7,  0 }, {  7,  0 }, {  7,  1 }, {  8,  0 }, {  8,  1 }, {  8,  1 },
  101.     {  8,  2 }, {  9,  1 }, {  9,  2 }, {  9,  2 }, {  9,  3 }, { 10,  2 },
  102.     { 10,  3 }, { 10,  3 }, { 10,  4 }, { 11,  3 }, { 11,  4 }, { 11,  4 },
  103.     { 11,  5 }, { 12,  4 }, { 12,  5 }, { 12,  5 }, { 12,  6 }, { 13,  5 },
  104.     { 13,  6 }, {  8, 16 }, { 13,  7 }, { 14,  6 }, { 14,  7 }, {  9, 17 },
  105.     { 14,  8 }, { 15,  7 }, { 15,  8 }, { 11, 16 }, { 15,  9 }, { 15, 10 },
  106.     { 16,  8 }, { 16,  9 }, { 16, 10 }, { 15, 13 }, { 17,  9 }, { 17, 10 },
  107.     { 17, 11 }, { 15, 16 }, { 18, 10 }, { 18, 11 }, { 18, 12 }, { 16, 16 },
  108.     { 19, 11 }, { 19, 12 }, { 19, 13 }, { 17, 17 }, { 20, 12 }, { 20, 13 },
  109.     { 20, 14 }, { 19, 16 }, { 21, 13 }, { 21, 14 }, { 21, 15 }, { 20, 17 },
  110.     { 22, 14 }, { 22, 15 }, { 25, 10 }, { 22, 16 }, { 23, 15 }, { 23, 16 },
  111.     { 26, 11 }, { 23, 17 }, { 24, 16 }, { 24, 17 }, { 27, 12 }, { 24, 18 },
  112.     { 25, 17 }, { 25, 18 }, { 28, 13 }, { 25, 19 }, { 26, 18 }, { 26, 19 },
  113.     { 29, 14 }, { 26, 20 }, { 27, 19 }, { 27, 20 }, { 30, 15 }, { 27, 21 },
  114.     { 28, 20 }, { 28, 21 }, { 28, 21 }, { 28, 22 }, { 29, 21 }, { 29, 22 },
  115.     { 24, 32 }, { 29, 23 }, { 30, 22 }, { 30, 23 }, { 25, 33 }, { 30, 24 },
  116.     { 31, 23 }, { 31, 24 }, { 27, 32 }, { 31, 25 }, { 31, 26 }, { 32, 24 },
  117.     { 32, 25 }, { 32, 26 }, { 31, 29 }, { 33, 25 }, { 33, 26 }, { 33, 27 },
  118.     { 31, 32 }, { 34, 26 }, { 34, 27 }, { 34, 28 }, { 32, 32 }, { 35, 27 },
  119.     { 35, 28 }, { 35, 29 }, { 33, 33 }, { 36, 28 }, { 36, 29 }, { 36, 30 },
  120.     { 35, 32 }, { 37, 29 }, { 37, 30 }, { 37, 31 }, { 36, 33 }, { 38, 30 },
  121.     { 38, 31 }, { 41, 26 }, { 38, 32 }, { 39, 31 }, { 39, 32 }, { 42, 27 },
  122.     { 39, 33 }, { 40, 32 }, { 40, 33 }, { 43, 28 }, { 40, 34 }, { 41, 33 },
  123.     { 41, 34 }, { 44, 29 }, { 41, 35 }, { 42, 34 }, { 42, 35 }, { 45, 30 },
  124.     { 42, 36 }, { 43, 35 }, { 43, 36 }, { 46, 31 }, { 43, 37 }, { 44, 36 },
  125.     { 44, 37 }, { 44, 37 }, { 44, 38 }, { 45, 37 }, { 45, 38 }, { 40, 48 },
  126.     { 45, 39 }, { 46, 38 }, { 46, 39 }, { 41, 49 }, { 46, 40 }, { 47, 39 },
  127.     { 47, 40 }, { 43, 48 }, { 47, 41 }, { 47, 42 }, { 48, 40 }, { 48, 41 },
  128.     { 48, 42 }, { 47, 45 }, { 49, 41 }, { 49, 42 }, { 49, 43 }, { 47, 48 },
  129.     { 50, 42 }, { 50, 43 }, { 50, 44 }, { 48, 48 }, { 51, 43 }, { 51, 44 },
  130.     { 51, 45 }, { 49, 49 }, { 52, 44 }, { 52, 45 }, { 52, 46 }, { 51, 48 },
  131.     { 53, 45 }, { 53, 46 }, { 53, 47 }, { 52, 49 }, { 54, 46 }, { 54, 47 },
  132.     { 57, 42 }, { 54, 48 }, { 55, 47 }, { 55, 48 }, { 58, 43 }, { 55, 49 },
  133.     { 56, 48 }, { 56, 49 }, { 59, 44 }, { 56, 50 }, { 57, 49 }, { 57, 50 },
  134.     { 60, 45 }, { 57, 51 }, { 58, 50 }, { 58, 51 }, { 61, 46 }, { 58, 52 },
  135.     { 59, 51 }, { 59, 52 }, { 62, 47 }, { 59, 53 }, { 60, 52 }, { 60, 53 },
  136.     { 60, 53 }, { 60, 54 }, { 61, 53 }, { 61, 54 }, { 61, 54 }, { 61, 55 },
  137.     { 62, 54 }, { 62, 55 }, { 62, 55 }, { 62, 56 }, { 63, 55 }, { 63, 56 },
  138.     { 63, 56 }, { 63, 57 }, { 63, 58 }, { 63, 59 }, { 63, 59 }, { 63, 60 },
  139.     { 63, 61 }, { 63, 62 }, { 63, 62 }, { 63, 63 },
  140. };
  141.  
  142. /* Multiplication over 8 bit emulation */
  143. #define mul8(a, b) (((a) * (b) + 128 + (((a) * (b) + 128) >> 8)) >> 8)
  144.  
  145. /* Conversion from rgb24 to rgb565 */
  146. #define rgb2rgb565(r, g, b) \
  147.     ((mul8(r, 31) << 11) | (mul8(g, 63) << 5) | (mul8(b, 31) << 0))
  148.  
  149. /* Linear interpolation at 1/3 point between a and b */
  150. #define lerp13(a, b) ((2 * (a) + (b)) / 3)
  151.  
  152. /* Linear interpolation on an RGB pixel */
  153. static inline void lerp13rgb(uint8_t *out, uint8_t *p1, uint8_t *p2)
  154. {
  155.     out[0] = lerp13(p1[0], p2[0]);
  156.     out[1] = lerp13(p1[1], p2[1]);
  157.     out[2] = lerp13(p1[2], p2[2]);
  158. }
  159.  
  160. /* Conversion from rgb565 to rgb24 */
  161. static inline void rgb5652rgb(uint8_t *out, uint16_t v)
  162. {
  163.     int rv = (v & 0xf800) >> 11;
  164.     int gv = (v & 0x07e0) >> 5;
  165.     int bv = (v & 0x001f) >> 0;
  166.  
  167.     out[0] = expand5[rv];
  168.     out[1] = expand6[gv];
  169.     out[2] = expand5[bv];
  170.     out[3] = 0;
  171. }
  172.  
  173. /* Color matching function */
  174. static unsigned int match_colors(const uint8_t *block, ptrdiff_t stride,
  175.                                  uint16_t c0, uint16_t c1)
  176. {
  177.     uint32_t mask = 0;
  178.     int dirr, dirg, dirb;
  179.     int dots[16];
  180.     int stops[4];
  181.     int x, y, k = 0;
  182.     int c0_point, half_point, c3_point;
  183.     uint8_t color[16];
  184.     const int indexMap[8] = {
  185.         0 << 30, 2 << 30, 0 << 30, 2 << 30,
  186.         3 << 30, 3 << 30, 1 << 30, 1 << 30,
  187.     };
  188.  
  189.     /* Fill color and compute direction for each component */
  190.     rgb5652rgb(color + 0, c0);
  191.     rgb5652rgb(color + 4, c1);
  192.     lerp13rgb(color + 8, color + 0, color + 4);
  193.     lerp13rgb(color + 12, color + 4, color + 0);
  194.  
  195.     dirr = color[0 * 4 + 0] - color[1 * 4 + 0];
  196.     dirg = color[0 * 4 + 1] - color[1 * 4 + 1];
  197.     dirb = color[0 * 4 + 2] - color[1 * 4 + 2];
  198.  
  199.     for (y = 0; y < 4; y++) {
  200.         for (x = 0; x < 4; x++)
  201.             dots[k++] = block[0 + x * 4 + y * stride] * dirr +
  202.                         block[1 + x * 4 + y * stride] * dirg +
  203.                         block[2 + x * 4 + y * stride] * dirb;
  204.  
  205.         stops[y] = color[0 + y * 4] * dirr +
  206.                    color[1 + y * 4] * dirg +
  207.                    color[2 + y * 4] * dirb;
  208.     }
  209.  
  210.     /* Think of the colors as arranged on a line; project point onto that line,
  211.      * then choose next color out of available ones. we compute the crossover
  212.      * points for 'best color in top half'/'best in bottom half' and then
  213.      * the same inside that subinterval.
  214.      *
  215.      * Relying on this 1d approximation isn't always optimal in terms of
  216.      * euclidean distance, but it's very close and a lot faster.
  217.      *
  218.      * http://cbloomrants.blogspot.com/2008/12/12-08-08-dxtc-summary.html */
  219.     c0_point   = (stops[1] + stops[3]) >> 1;
  220.     half_point = (stops[3] + stops[2]) >> 1;
  221.     c3_point   = (stops[2] + stops[0]) >> 1;
  222.  
  223.     for (x = 0; x < 16; x++) {
  224.         int dot  = dots[x];
  225.         int bits = (dot < half_point ? 4 : 0) |
  226.                    (dot < c0_point   ? 2 : 0) |
  227.                    (dot < c3_point   ? 1 : 0);
  228.  
  229.         mask >>= 2;
  230.         mask  |= indexMap[bits];
  231.     }
  232.  
  233.     return mask;
  234. }
  235.  
  236. /* Color optimization function */
  237. static void optimize_colors(const uint8_t *block, ptrdiff_t stride,
  238.                             uint16_t *pmax16, uint16_t *pmin16)
  239. {
  240.     const uint8_t *minp;
  241.     const uint8_t *maxp;
  242.     const int iter_power = 4;
  243.     double magn;
  244.     int v_r, v_g, v_b;
  245.     float covf[6], vfr, vfg, vfb;
  246.     int mind, maxd;
  247.     int cov[6] = { 0 };
  248.     int mu[3], min[3], max[3];
  249.     int ch, iter, x, y;
  250.  
  251.     /* Determine color distribution */
  252.     for (ch = 0; ch < 3; ch++) {
  253.         const uint8_t *bp = &block[ch];
  254.         int muv, minv, maxv;
  255.  
  256.         muv = minv = maxv = bp[0];
  257.         for (y = 0; y < 4; y++) {
  258.             for (x = 4; x < 4; x += 4) {
  259.                 muv += bp[x * 4 + y * stride];
  260.                 if (bp[x] < minv)
  261.                     minv = bp[x * 4 + y * stride];
  262.                 else if (bp[x] > maxv)
  263.                     maxv = bp[x * 4 + y * stride];
  264.             }
  265.         }
  266.  
  267.         mu[ch]  = (muv + 8) >> 4;
  268.         min[ch] = minv;
  269.         max[ch] = maxv;
  270.     }
  271.  
  272.     /* Determine covariance matrix */
  273.     for (y = 0; y < 4; y++) {
  274.         for (x = 0; x < 4; x++) {
  275.             int r = block[x * 4 + stride * y + 0] - mu[0];
  276.             int g = block[x * 4 + stride * y + 1] - mu[1];
  277.             int b = block[x * 4 + stride * y + 2] - mu[2];
  278.  
  279.             cov[0] += r * r;
  280.             cov[1] += r * g;
  281.             cov[2] += r * b;
  282.             cov[3] += g * g;
  283.             cov[4] += g * b;
  284.             cov[5] += b * b;
  285.         }
  286.     }
  287.  
  288.     /* Convert covariance matrix to float, find principal axis via power iter */
  289.     for (x = 0; x < 6; x++)
  290.         covf[x] = cov[x] / 255.0f;
  291.  
  292.     vfr = (float) (max[0] - min[0]);
  293.     vfg = (float) (max[1] - min[1]);
  294.     vfb = (float) (max[2] - min[2]);
  295.  
  296.     for (iter = 0; iter < iter_power; iter++) {
  297.         float r = vfr * covf[0] + vfg * covf[1] + vfb * covf[2];
  298.         float g = vfr * covf[1] + vfg * covf[3] + vfb * covf[4];
  299.         float b = vfr * covf[2] + vfg * covf[4] + vfb * covf[5];
  300.  
  301.         vfr = r;
  302.         vfg = g;
  303.         vfb = b;
  304.     }
  305.  
  306.     magn = fabs(vfr);
  307.     if (fabs(vfg) > magn)
  308.         magn = fabs(vfg);
  309.     if (fabs(vfb) > magn)
  310.         magn = fabs(vfb);
  311.  
  312.     /* if magnitudo is too small, default to luminance */
  313.     if (magn < 4.0f) {
  314.         /* JPEG YCbCr luma coefs, scaled by 1000 */
  315.         v_r = 299;
  316.         v_g = 587;
  317.         v_b = 114;
  318.     } else {
  319.         magn = 512.0 / magn;
  320.         v_r  = (int) (vfr * magn);
  321.         v_g  = (int) (vfg * magn);
  322.         v_b  = (int) (vfb * magn);
  323.     }
  324.  
  325.     /* Pick colors at extreme points */
  326.     mind = maxd = block[0] * v_r + block[1] * v_g + block[2] * v_b;
  327.     minp = maxp = block;
  328.     for (y = 0; y < 4; y++) {
  329.         for (x = 0; x < 4; x++) {
  330.             int dot = block[x * 4 + y * stride + 0] * v_r +
  331.                       block[x * 4 + y * stride + 1] * v_g +
  332.                       block[x * 4 + y * stride + 2] * v_b;
  333.  
  334.             if (dot < mind) {
  335.                 mind = dot;
  336.                 minp = block + x * 4 + y * stride;
  337.             } else if (dot > maxd) {
  338.                 maxd = dot;
  339.                 maxp = block + x * 4 + y * stride;
  340.             }
  341.         }
  342.     }
  343.  
  344.     *pmax16 = rgb2rgb565(maxp[0], maxp[1], maxp[2]);
  345.     *pmin16 = rgb2rgb565(minp[0], minp[1], minp[2]);
  346. }
  347.  
  348. /* Try to optimize colors to suit block contents better, by solving
  349.  * a least squares system via normal equations + Cramer's rule. */
  350. static int refine_colors(const uint8_t *block, ptrdiff_t stride,
  351.                          uint16_t *pmax16, uint16_t *pmin16, uint32_t mask)
  352. {
  353.     uint32_t cm = mask;
  354.     uint16_t oldMin = *pmin16;
  355.     uint16_t oldMax = *pmax16;
  356.     uint16_t min16, max16;
  357.     int x, y;
  358.  
  359.     /* Additional magic to save a lot of multiplies in the accumulating loop.
  360.      * The tables contain precomputed products of weights for least squares
  361.      * system, accumulated inside one 32-bit register */
  362.     const int w1tab[4] = { 3, 0, 2, 1 };
  363.     const int prods[4] = { 0x090000, 0x000900, 0x040102, 0x010402 };
  364.  
  365.     /* Check if all pixels have the same index */
  366.     if ((mask ^ (mask << 2)) < 4) {
  367.         /* If so, linear system would be singular; solve using optimal
  368.          * single-color match on average color. */
  369.         int r = 8, g = 8, b = 8;
  370.         for (y = 0; y < 4; y++) {
  371.             for (x = 0; x < 4; x++) {
  372.                 r += block[0 + x * 4 + y * stride];
  373.                 g += block[1 + x * 4 + y * stride];
  374.                 b += block[2 + x * 4 + y * stride];
  375.             }
  376.         }
  377.  
  378.         r >>= 4;
  379.         g >>= 4;
  380.         b >>= 4;
  381.  
  382.         max16 = (match5[r][0] << 11) | (match6[g][0] << 5) | match5[b][0];
  383.         min16 = (match5[r][1] << 11) | (match6[g][1] << 5) | match5[b][1];
  384.     } else {
  385.         float fr, fg, fb;
  386.         int at1_r = 0, at1_g = 0, at1_b = 0;
  387.         int at2_r = 0, at2_g = 0, at2_b = 0;
  388.         int akku = 0;
  389.         int xx, xy, yy;
  390.  
  391.         for (y = 0; y < 4; y++) {
  392.             for (x = 0; x < 4; x++) {
  393.                 int step = cm & 3;
  394.                 int w1 = w1tab[step];
  395.                 int r = block[0 + x * 4 + y * stride];
  396.                 int g = block[1 + x * 4 + y * stride];
  397.                 int b = block[2 + x * 4 + y * stride];
  398.  
  399.                 akku  += prods[step];
  400.                 at1_r += w1 * r;
  401.                 at1_g += w1 * g;
  402.                 at1_b += w1 * b;
  403.                 at2_r += r;
  404.                 at2_g += g;
  405.                 at2_b += b;
  406.  
  407.                 cm >>= 2;
  408.             }
  409.         }
  410.  
  411.         at2_r = 3 * at2_r - at1_r;
  412.         at2_g = 3 * at2_g - at1_g;
  413.         at2_b = 3 * at2_b - at1_b;
  414.  
  415.         /* Extract solutions and decide solvability */
  416.         xx =  akku >> 16;
  417.         yy = (akku >>  8) & 0xFF;
  418.         xy = (akku >>  0) & 0xFF;
  419.  
  420.         fr = 3.0f * 31.0f / 255.0f / (xx * yy - xy * xy);
  421.         fg = fr * 63.0f / 31.0f;
  422.         fb = fr;
  423.  
  424.         /* Solve */
  425.         max16  = av_clip_uintp2((at1_r * yy - at2_r * xy) * fr + 0.5f, 5) << 11;
  426.         max16 |= av_clip_uintp2((at1_g * yy - at2_g * xy) * fg + 0.5f, 6) <<  5;
  427.         max16 |= av_clip_uintp2((at1_b * yy - at2_b * xy) * fb + 0.5f, 5) <<  0;
  428.  
  429.         min16  = av_clip_uintp2((at2_r * xx - at1_r * xy) * fr + 0.5f, 5) << 11;
  430.         min16 |= av_clip_uintp2((at2_g * xx - at1_g * xy) * fg + 0.5f, 6) <<  5;
  431.         min16 |= av_clip_uintp2((at2_b * xx - at1_b * xy) * fb + 0.5f, 5) <<  0;
  432.     }
  433.  
  434.     *pmin16 = min16;
  435.     *pmax16 = max16;
  436.     return oldMin != min16 || oldMax != max16;
  437. }
  438.  
  439. /* Check if input block is a constant color */
  440. static int constant_color(const uint8_t *block, ptrdiff_t stride)
  441. {
  442.     int x, y;
  443.     uint32_t first = AV_RL32(block);
  444.  
  445.     for (y = 0; y < 4; y++)
  446.         for (x = 0; x < 4; x++)
  447.             if (first != AV_RL32(block + x * 4 + y * stride))
  448.                 return 0;
  449.     return 1;
  450. }
  451.  
  452. /* Main color compression function */
  453. static void compress_color(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
  454. {
  455.     uint32_t mask;
  456.     uint16_t max16, min16;
  457.     int constant = constant_color(block, stride);
  458.  
  459.     /* Constant color will load values from tables */
  460.     if (constant) {
  461.         int r = block[0];
  462.         int g = block[1];
  463.         int b = block[2];
  464.         mask  = 0xAAAAAAAA;
  465.         max16 = (match5[r][0] << 11) | (match6[g][0] << 5) | match5[b][0];
  466.         min16 = (match5[r][1] << 11) | (match6[g][1] << 5) | match5[b][1];
  467.     } else {
  468.         int refine;
  469.  
  470.         /* Otherwise find pca and map along principal axis */
  471.         optimize_colors(block, stride, &max16, &min16);
  472.         if (max16 != min16)
  473.             mask = match_colors(block, stride, max16, min16);
  474.         else
  475.             mask = 0;
  476.  
  477.         /* One pass refinement */
  478.         refine  = refine_colors(block, stride, &max16, &min16, mask);
  479.         if (refine) {
  480.             if (max16 != min16)
  481.                 mask = match_colors(block, stride, max16, min16);
  482.             else
  483.                 mask = 0;
  484.         }
  485.     }
  486.  
  487.     /* Finally write the color block */
  488.     if (max16 < min16) {
  489.         FFSWAP(uint16_t, min16, max16);
  490.         mask ^= 0x55555555;
  491.     }
  492.  
  493.     AV_WL16(dst + 0, max16);
  494.     AV_WL16(dst + 2, min16);
  495.     AV_WL32(dst + 4, mask);
  496. }
  497.  
  498. /* Alpha compression function */
  499. static void compress_alpha(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
  500. {
  501.     int x, y;
  502.     int dist, bias, dist4, dist2;
  503.     int mn, mx;
  504.     int bits = 0;
  505.     int mask = 0;
  506.  
  507.     memset(dst, 0, 8);
  508.  
  509.     /* Find min/max color */
  510.     mn = mx = block[3];
  511.     for (y = 0; y < 4; y++) {
  512.         for (x = 0; x < 4; x++) {
  513.             int val = block[3 + x * 4 + y * stride];
  514.             if (val < mn)
  515.                 mn = val;
  516.             else if (val > mx)
  517.                 mx = val;
  518.         }
  519.     }
  520.  
  521.     /* Encode them */
  522.     dst[0] = (uint8_t) mx;
  523.     dst[1] = (uint8_t) mn;
  524.     dst += 2;
  525.  
  526.     /* Mono-alpha shortcut */
  527.     if (mn == mx)
  528.         return;
  529.  
  530.     /* Determine bias and emit color indices.
  531.      * Given the choice of mx/mn, these indices are optimal:
  532.      * fgiesen.wordpress.com/2009/12/15/dxt5-alpha-block-index-determination */
  533.     dist = mx - mn;
  534.  
  535.     dist4 = dist * 4;
  536.     dist2 = dist * 2;
  537.     if (dist < 8)
  538.         bias = dist - 1 - mn * 7;
  539.     else
  540.         bias = dist / 2 + 2 - mn * 7;
  541.  
  542.     for (y = 0; y < 4; y++) {
  543.         for (x = 0; x < 4; x++) {
  544.             int alp = block[3 + x * 4 + y * stride] * 7 + bias;
  545.             int ind, tmp;
  546.  
  547.             /* This is a "linear scale" lerp factor between 0 (val=min)
  548.              * and 7 (val=max) to select index. */
  549.             tmp  = (alp >= dist4) ? -1 : 0;
  550.             ind  = tmp & 4;
  551.             alp -= dist4 & tmp;
  552.             tmp  = (alp >= dist2) ? -1 : 0;
  553.             ind += tmp & 2;
  554.             alp -= dist2 & tmp;
  555.             ind += (alp >= dist);
  556.  
  557.             /* Turn linear scale into DXT index (0/1 are extreme points) */
  558.             ind  = -ind & 7;
  559.             ind ^= (2 > ind);
  560.  
  561.             /* Write index */
  562.             mask |= ind << bits;
  563.             bits += 3;
  564.             if (bits >= 8) {
  565.                 *dst++ = mask;
  566.                 mask >>= 8;
  567.                 bits  -= 8;
  568.             }
  569.         }
  570.     }
  571. }
  572.  
  573. /**
  574.  * Convert a RGBA buffer to unscaled YCoCg.
  575.  * Scale is usually introduced to avoid banding over a certain range of colors,
  576.  * but this version of the algorithm does not introduce it as much as other
  577.  * implementations, allowing for a simpler and faster conversion.
  578.  */
  579. static void rgba2ycocg(uint8_t *dst, const uint8_t *pixel)
  580. {
  581.     int r =  pixel[0];
  582.     int g = (pixel[1] + 1) >> 1;
  583.     int b =  pixel[2];
  584.     int t = (2 + r + b) >> 2;
  585.  
  586.     int y  = av_clip_uint8(g + t);
  587.     int co = av_clip_uint8(128 + ((r - b + 1) >> 1));
  588.     int cg = av_clip_uint8(128 + g - t);
  589.  
  590.     dst[0] = (uint8_t) co;
  591.     dst[1] = (uint8_t) cg;
  592.     dst[2] = 0;
  593.     dst[3] = (uint8_t) y;
  594. }
  595.  
  596. /**
  597.  * Compress one block of RGBA pixels in a DXT1 texture and store the
  598.  * resulting bytes in 'dst'. Alpha is not preserved.
  599.  *
  600.  * @param dst    output buffer.
  601.  * @param stride scanline in bytes.
  602.  * @param block  block to compress.
  603.  * @return how much texture data has been written.
  604.  */
  605. static int dxt1_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
  606. {
  607.     compress_color(dst, stride, block);
  608.  
  609.     return 8;
  610. }
  611.  
  612. /**
  613.  * Compress one block of RGBA pixels in a DXT5 texture and store the
  614.  * resulting bytes in 'dst'. Alpha is preserved.
  615.  *
  616.  * @param dst    output buffer.
  617.  * @param stride scanline in bytes.
  618.  * @param block  block to compress.
  619.  * @return how much texture data has been written.
  620.  */
  621. static int dxt5_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
  622. {
  623.     compress_alpha(dst, stride, block);
  624.     compress_color(dst + 8, stride, block);
  625.  
  626.     return 16;
  627. }
  628.  
  629. /**
  630.  * Compress one block of RGBA pixels in a DXT5-YCoCg texture and store the
  631.  * resulting bytes in 'dst'. Alpha is not preserved.
  632.  *
  633.  * @param dst    output buffer.
  634.  * @param stride scanline in bytes.
  635.  * @param block  block to compress.
  636.  * @return how much texture data has been written.
  637.  */
  638. static int dxt5ys_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
  639. {
  640.     int x, y;
  641.     uint8_t reorder[64];
  642.  
  643.     /* Reorder the components and then run a normal DXT5 compression. */
  644.     for (y = 0; y < 4; y++)
  645.         for (x = 0; x < 4; x++)
  646.             rgba2ycocg(reorder + x * 4 + y * 16, block + x * 4 + y * stride);
  647.  
  648.     compress_alpha(dst + 0, 16, reorder);
  649.     compress_color(dst + 8, 16, reorder);
  650.  
  651.     return 16;
  652. }
  653.  
  654. av_cold void ff_texturedspenc_init(TextureDSPContext *c)
  655. {
  656.     c->dxt1_block   = dxt1_block;
  657.     c->dxt5_block   = dxt5_block;
  658.     c->dxt5ys_block = dxt5ys_block;
  659. }
  660.