Introduce a TextureDSP module

This module implements generic texture decompression from different
families (DXTC, RGTC, BCn) and texture compression DXTC 1, 3, and 5.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 659 insertions, 0 deletions

diff --git a/libavcodec/texturedspenc.c b/libavcodec/texturedspenc.c
new file mode 100644
index 0000000000..4a387c5edc
--- /dev/null
+++ b/libavcodec/texturedspenc.c
@@ -0,0 +1,659 @@
+/*
+ * Texture block compression
+ * Copyright (C) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>
+ * Based on public domain code by Fabian Giesen, Sean Barrett and Yann Collet.
+ *
+ * This file is part of Libav
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "libavutil/attributes.h"
+#include "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+
+#include "texturedsp.h"
+
+const static uint8_t expand5[32] = {
+      0,   8,  16,  24,  33,  41,  49,  57,  66,  74,  82,  90,
+     99, 107, 115, 123, 132, 140, 148, 156, 165, 173, 181, 189,
+    198, 206, 214, 222, 231, 239, 247, 255,
+};
+
+const static uint8_t expand6[64] = {
+      0,   4,   8,  12,  16,  20,  24,  28,  32,  36,  40,  44,
+     48,  52,  56,  60,  65,  69,  73,  77,  81,  85,  89,  93,
+     97, 101, 105, 109, 113, 117, 121, 125, 130, 134, 138, 142,
+    146, 150, 154, 158, 162, 166, 170, 174, 178, 182, 186, 190,
+    195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239,
+    243, 247, 251, 255,
+};
+
+const static uint8_t match5[256][2] = {
+    {  0,  0 }, {  0,  0 }, {  0,  1 }, {  0,  1 }, {  1,  0 }, {  1,  0 },
+    {  1,  0 }, {  1,  1 }, {  1,  1 }, {  2,  0 }, {  2,  0 }, {  0,  4 },
+    {  2,  1 }, {  2,  1 }, {  2,  1 }, {  3,  0 }, {  3,  0 }, {  3,  0 },
+    {  3,  1 }, {  1,  5 }, {  3,  2 }, {  3,  2 }, {  4,  0 }, {  4,  0 },
+    {  4,  1 }, {  4,  1 }, {  4,  2 }, {  4,  2 }, {  4,  2 }, {  3,  5 },
+    {  5,  1 }, {  5,  1 }, {  5,  2 }, {  4,  4 }, {  5,  3 }, {  5,  3 },
+    {  5,  3 }, {  6,  2 }, {  6,  2 }, {  6,  2 }, {  6,  3 }, {  5,  5 },
+    {  6,  4 }, {  6,  4 }, {  4,  8 }, {  7,  3 }, {  7,  3 }, {  7,  3 },
+    {  7,  4 }, {  7,  4 }, {  7,  4 }, {  7,  5 }, {  5,  9 }, {  7,  6 },
+    {  7,  6 }, {  8,  4 }, {  8,  4 }, {  8,  5 }, {  8,  5 }, {  8,  6 },
+    {  8,  6 }, {  8,  6 }, {  7,  9 }, {  9,  5 }, {  9,  5 }, {  9,  6 },
+    {  8,  8 }, {  9,  7 }, {  9,  7 }, {  9,  7 }, { 10,  6 }, { 10,  6 },
+    { 10,  6 }, { 10,  7 }, {  9,  9 }, { 10,  8 }, { 10,  8 }, {  8, 12 },
+    { 11,  7 }, { 11,  7 }, { 11,  7 }, { 11,  8 }, { 11,  8 }, { 11,  8 },
+    { 11,  9 }, {  9, 13 }, { 11, 10 }, { 11, 10 }, { 12,  8 }, { 12,  8 },
+    { 12,  9 }, { 12,  9 }, { 12, 10 }, { 12, 10 }, { 12, 10 }, { 11, 13 },
+    { 13,  9 }, { 13,  9 }, { 13, 10 }, { 12, 12 }, { 13, 11 }, { 13, 11 },
+    { 13, 11 }, { 14, 10 }, { 14, 10 }, { 14, 10 }, { 14, 11 }, { 13, 13 },
+    { 14, 12 }, { 14, 12 }, { 12, 16 }, { 15, 11 }, { 15, 11 }, { 15, 11 },
+    { 15, 12 }, { 15, 12 }, { 15, 12 }, { 15, 13 }, { 13, 17 }, { 15, 14 },
+    { 15, 14 }, { 16, 12 }, { 16, 12 }, { 16, 13 }, { 16, 13 }, { 16, 14 },
+    { 16, 14 }, { 16, 14 }, { 15, 17 }, { 17, 13 }, { 17, 13 }, { 17, 14 },
+    { 16, 16 }, { 17, 15 }, { 17, 15 }, { 17, 15 }, { 18, 14 }, { 18, 14 },
+    { 18, 14 }, { 18, 15 }, { 17, 17 }, { 18, 16 }, { 18, 16 }, { 16, 20 },
+    { 19, 15 }, { 19, 15 }, { 19, 15 }, { 19, 16 }, { 19, 16 }, { 19, 16 },
+    { 19, 17 }, { 17, 21 }, { 19, 18 }, { 19, 18 }, { 20, 16 }, { 20, 16 },
+    { 20, 17 }, { 20, 17 }, { 20, 18 }, { 20, 18 }, { 20, 18 }, { 19, 21 },
+    { 21, 17 }, { 21, 17 }, { 21, 18 }, { 20, 20 }, { 21, 19 }, { 21, 19 },
+    { 21, 19 }, { 22, 18 }, { 22, 18 }, { 22, 18 }, { 22, 19 }, { 21, 21 },
+    { 22, 20 }, { 22, 20 }, { 20, 24 }, { 23, 19 }, { 23, 19 }, { 23, 19 },
+    { 23, 20 }, { 23, 20 }, { 23, 20 }, { 23, 21 }, { 21, 25 }, { 23, 22 },
+    { 23, 22 }, { 24, 20 }, { 24, 20 }, { 24, 21 }, { 24, 21 }, { 24, 22 },
+    { 24, 22 }, { 24, 22 }, { 23, 25 }, { 25, 21 }, { 25, 21 }, { 25, 22 },
+    { 24, 24 }, { 25, 23 }, { 25, 23 }, { 25, 23 }, { 26, 22 }, { 26, 22 },
+    { 26, 22 }, { 26, 23 }, { 25, 25 }, { 26, 24 }, { 26, 24 }, { 24, 28 },
+    { 27, 23 }, { 27, 23 }, { 27, 23 }, { 27, 24 }, { 27, 24 }, { 27, 24 },
+    { 27, 25 }, { 25, 29 }, { 27, 26 }, { 27, 26 }, { 28, 24 }, { 28, 24 },
+    { 28, 25 }, { 28, 25 }, { 28, 26 }, { 28, 26 }, { 28, 26 }, { 27, 29 },
+    { 29, 25 }, { 29, 25 }, { 29, 26 }, { 28, 28 }, { 29, 27 }, { 29, 27 },
+    { 29, 27 }, { 30, 26 }, { 30, 26 }, { 30, 26 }, { 30, 27 }, { 29, 29 },
+    { 30, 28 }, { 30, 28 }, { 30, 28 }, { 31, 27 }, { 31, 27 }, { 31, 27 },
+    { 31, 28 }, { 31, 28 }, { 31, 28 }, { 31, 29 }, { 31, 29 }, { 31, 30 },
+    { 31, 30 }, { 31, 30 }, { 31, 31 }, { 31, 31 },
+};
+
+const static uint8_t match6[256][2] = {
+    {  0,  0 }, {  0,  1 }, {  1,  0 }, {  1,  0 }, {  1,  1 }, {  2,  0 },
+    {  2,  1 }, {  3,  0 }, {  3,  0 }, {  3,  1 }, {  4,  0 }, {  4,  0 },
+    {  4,  1 }, {  5,  0 }, {  5,  1 }, {  6,  0 }, {  6,  0 }, {  6,  1 },
+    {  7,  0 }, {  7,  0 }, {  7,  1 }, {  8,  0 }, {  8,  1 }, {  8,  1 },
+    {  8,  2 }, {  9,  1 }, {  9,  2 }, {  9,  2 }, {  9,  3 }, { 10,  2 },
+    { 10,  3 }, { 10,  3 }, { 10,  4 }, { 11,  3 }, { 11,  4 }, { 11,  4 },
+    { 11,  5 }, { 12,  4 }, { 12,  5 }, { 12,  5 }, { 12,  6 }, { 13,  5 },
+    { 13,  6 }, {  8, 16 }, { 13,  7 }, { 14,  6 }, { 14,  7 }, {  9, 17 },
+    { 14,  8 }, { 15,  7 }, { 15,  8 }, { 11, 16 }, { 15,  9 }, { 15, 10 },
+    { 16,  8 }, { 16,  9 }, { 16, 10 }, { 15, 13 }, { 17,  9 }, { 17, 10 },
+    { 17, 11 }, { 15, 16 }, { 18, 10 }, { 18, 11 }, { 18, 12 }, { 16, 16 },
+    { 19, 11 }, { 19, 12 }, { 19, 13 }, { 17, 17 }, { 20, 12 }, { 20, 13 },
+    { 20, 14 }, { 19, 16 }, { 21, 13 }, { 21, 14 }, { 21, 15 }, { 20, 17 },
+    { 22, 14 }, { 22, 15 }, { 25, 10 }, { 22, 16 }, { 23, 15 }, { 23, 16 },
+    { 26, 11 }, { 23, 17 }, { 24, 16 }, { 24, 17 }, { 27, 12 }, { 24, 18 },
+    { 25, 17 }, { 25, 18 }, { 28, 13 }, { 25, 19 }, { 26, 18 }, { 26, 19 },
+    { 29, 14 }, { 26, 20 }, { 27, 19 }, { 27, 20 }, { 30, 15 }, { 27, 21 },
+    { 28, 20 }, { 28, 21 }, { 28, 21 }, { 28, 22 }, { 29, 21 }, { 29, 22 },
+    { 24, 32 }, { 29, 23 }, { 30, 22 }, { 30, 23 }, { 25, 33 }, { 30, 24 },
+    { 31, 23 }, { 31, 24 }, { 27, 32 }, { 31, 25 }, { 31, 26 }, { 32, 24 },
+    { 32, 25 }, { 32, 26 }, { 31, 29 }, { 33, 25 }, { 33, 26 }, { 33, 27 },
+    { 31, 32 }, { 34, 26 }, { 34, 27 }, { 34, 28 }, { 32, 32 }, { 35, 27 },
+    { 35, 28 }, { 35, 29 }, { 33, 33 }, { 36, 28 }, { 36, 29 }, { 36, 30 },
+    { 35, 32 }, { 37, 29 }, { 37, 30 }, { 37, 31 }, { 36, 33 }, { 38, 30 },
+    { 38, 31 }, { 41, 26 }, { 38, 32 }, { 39, 31 }, { 39, 32 }, { 42, 27 },
+    { 39, 33 }, { 40, 32 }, { 40, 33 }, { 43, 28 }, { 40, 34 }, { 41, 33 },
+    { 41, 34 }, { 44, 29 }, { 41, 35 }, { 42, 34 }, { 42, 35 }, { 45, 30 },
+    { 42, 36 }, { 43, 35 }, { 43, 36 }, { 46, 31 }, { 43, 37 }, { 44, 36 },
+    { 44, 37 }, { 44, 37 }, { 44, 38 }, { 45, 37 }, { 45, 38 }, { 40, 48 },
+    { 45, 39 }, { 46, 38 }, { 46, 39 }, { 41, 49 }, { 46, 40 }, { 47, 39 },
+    { 47, 40 }, { 43, 48 }, { 47, 41 }, { 47, 42 }, { 48, 40 }, { 48, 41 },
+    { 48, 42 }, { 47, 45 }, { 49, 41 }, { 49, 42 }, { 49, 43 }, { 47, 48 },
+    { 50, 42 }, { 50, 43 }, { 50, 44 }, { 48, 48 }, { 51, 43 }, { 51, 44 },
+    { 51, 45 }, { 49, 49 }, { 52, 44 }, { 52, 45 }, { 52, 46 }, { 51, 48 },
+    { 53, 45 }, { 53, 46 }, { 53, 47 }, { 52, 49 }, { 54, 46 }, { 54, 47 },
+    { 57, 42 }, { 54, 48 }, { 55, 47 }, { 55, 48 }, { 58, 43 }, { 55, 49 },
+    { 56, 48 }, { 56, 49 }, { 59, 44 }, { 56, 50 }, { 57, 49 }, { 57, 50 },
+    { 60, 45 }, { 57, 51 }, { 58, 50 }, { 58, 51 }, { 61, 46 }, { 58, 52 },
+    { 59, 51 }, { 59, 52 }, { 62, 47 }, { 59, 53 }, { 60, 52 }, { 60, 53 },
+    { 60, 53 }, { 60, 54 }, { 61, 53 }, { 61, 54 }, { 61, 54 }, { 61, 55 },
+    { 62, 54 }, { 62, 55 }, { 62, 55 }, { 62, 56 }, { 63, 55 }, { 63, 56 },
+    { 63, 56 }, { 63, 57 }, { 63, 58 }, { 63, 59 }, { 63, 59 }, { 63, 60 },
+    { 63, 61 }, { 63, 62 }, { 63, 62 }, { 63, 63 },
+};
+
+/* Multiplication over 8 bit emulation */
+#define mul8(a, b) (a * b + 128 + ((a * b + 128) >> 8)) >> 8
+
+/* Conversion from rgb24 to rgb565 */
+#define rgb2rgb565(r, g, b) \
+    (mul8(r, 31) << 11) | (mul8(g, 63) << 5) | (mul8(b, 31) << 0)
+
+/* Linear interpolation at 1/3 point between a and b */
+#define lerp13(a, b) (2 * a + b) / 3
+
+/* Linear interpolation on an RGB pixel */
+static inline void lerp13rgb(uint8_t *out, uint8_t *p1, uint8_t *p2)
+{
+    out[0] = lerp13(p1[0], p2[0]);
+    out[1] = lerp13(p1[1], p2[1]);
+    out[2] = lerp13(p1[2], p2[2]);
+}
+
+/* Conversion from rgb565 to rgb24 */
+static inline void rgb5652rgb(uint8_t *out, uint16_t v)
+{
+    int rv = (v & 0xf800) >> 11;
+    int gv = (v & 0x07e0) >> 5;
+    int bv = (v & 0x001f) >> 0;
+
+    out[0] = expand5[rv];
+    out[1] = expand6[gv];
+    out[2] = expand5[bv];
+    out[3] = 0;
+}
+
+/* Color matching function */
+static unsigned int match_colors(const uint8_t *block, ptrdiff_t stride,
+                                 uint16_t c0, uint16_t c1)
+{
+    uint32_t mask = 0;
+    int dirr, dirg, dirb;
+    int dots[16];
+    int stops[4];
+    int x, y, k = 0;
+    int c0_point, half_point, c3_point;
+    uint8_t color[16];
+    const int indexMap[8] = {
+        0 << 30, 2 << 30, 0 << 30, 2 << 30,
+        3 << 30, 3 << 30, 1 << 30, 1 << 30,
+    };
+
+    /* Fill color and compute direction for each component */
+    rgb5652rgb(color + 0, c0);
+    rgb5652rgb(color + 4, c1);
+    lerp13rgb(color + 8, color + 0, color + 4);
+    lerp13rgb(color + 12, color + 4, color + 0);
+
+    dirr = color[0 * 4 + 0] - color[1 * 4 + 0];
+    dirg = color[0 * 4 + 1] - color[1 * 4 + 1];
+    dirb = color[0 * 4 + 2] - color[1 * 4 + 2];
+
+    for (y = 0; y < 4; y++) {
+        for (x = 0; x < 4; x++)
+            dots[k++] = block[0 + x * 4 + y * stride] * dirr +
+                        block[1 + x * 4 + y * stride] * dirg +
+                        block[2 + x * 4 + y * stride] * dirb;
+
+        stops[y] = color[0 + y * 4] * dirr +
+                   color[1 + y * 4] * dirg +
+                   color[2 + y * 4] * dirb;
+    }
+
+    /* Think of the colors as arranged on a line; project point onto that line,
+     * then choose next color out of available ones. we compute the crossover
+     * points for 'best color in top half'/'best in bottom half' and then
+     * the same inside that subinterval.
+     *
+     * Relying on this 1d approximation isn't always optimal in terms of
+     * euclidean distance, but it's very close and a lot faster.
+     *
+     * http://cbloomrants.blogspot.com/2008/12/12-08-08-dxtc-summary.html */
+    c0_point   = (stops[1] + stops[3]) >> 1;
+    half_point = (stops[3] + stops[2]) >> 1;
+    c3_point   = (stops[2] + stops[0]) >> 1;
+
+    for (x = 0; x < 16; x++) {
+        int dot  = dots[x];
+        int bits = (dot < half_point ? 4 : 0) |
+                   (dot < c0_point   ? 2 : 0) |
+                   (dot < c3_point   ? 1 : 0);
+
+        mask >>= 2;
+        mask  |= indexMap[bits];
+    }
+
+    return mask;
+}
+
+/* Color optimization function */
+static void optimize_colors(const uint8_t *block, ptrdiff_t stride,
+                            uint16_t *pmax16, uint16_t *pmin16)
+{
+    const uint8_t *minp;
+    const uint8_t *maxp;
+    const int iter_power = 4;
+    double magn;
+    int v_r, v_g, v_b;
+    float covf[6], vfr, vfg, vfb;
+    int mind, maxd;
+    int cov[6] = { 0 };
+    int mu[3], min[3], max[3];
+    int ch, iter, x, y;
+
+    /* Determine color distribution */
+    for (ch = 0; ch < 3; ch++) {
+        const uint8_t *bp = &block[ch];
+        int muv, minv, maxv;
+
+        muv = minv = maxv = bp[0];
+        for (y = 0; y < 4; y++) {
+            for (x = 4; x < 4; x += 4) {
+                muv += bp[x * 4 + y * stride];
+                if (bp[x] < minv)
+                    minv = bp[x * 4 + y * stride];
+                else if (bp[x] > maxv)
+                    maxv = bp[x * 4 + y * stride];
+            }
+        }
+
+        mu[ch]  = (muv + 8) >> 4;
+        min[ch] = minv;
+        max[ch] = maxv;
+    }
+
+    /* Determine covariance matrix */
+    for (y = 0; y < 4; y++) {
+        for (x = 0; x < 4; x++) {
+            int r = block[x * 4 + stride * y + 0] - mu[0];
+            int g = block[x * 4 + stride * y + 1] - mu[1];
+            int b = block[x * 4 + stride * y + 2] - mu[2];
+
+            cov[0] += r * r;
+            cov[1] += r * g;
+            cov[2] += r * b;
+            cov[3] += g * g;
+            cov[4] += g * b;
+            cov[5] += b * b;
+        }
+    }
+
+    /* Convert covariance matrix to float, find principal axis via power iter */
+    for (x = 0; x < 6; x++)
+        covf[x] = cov[x] / 255.0f;
+
+    vfr = (float) (max[0] - min[0]);
+    vfg = (float) (max[1] - min[1]);
+    vfb = (float) (max[2] - min[2]);
+
+    for (iter = 0; iter < iter_power; iter++) {
+        float r = vfr * covf[0] + vfg * covf[1] + vfb * covf[2];
+        float g = vfr * covf[1] + vfg * covf[3] + vfb * covf[4];
+        float b = vfr * covf[2] + vfg * covf[4] + vfb * covf[5];
+
+        vfr = r;
+        vfg = g;
+        vfb = b;
+    }
+
+    magn = fabs(vfr);
+    if (fabs(vfg) > magn)
+        magn = fabs(vfg);
+    if (fabs(vfb) > magn)
+        magn = fabs(vfb);
+
+    /* if magnitudo is too small, default to luminance */
+    if (magn < 4.0f) {
+        /* JPEG YCbCr luma coefs, scaled by 1000 */
+        v_r = 299;
+        v_g = 587;
+        v_b = 114;
+    } else {
+        magn = 512.0 / magn;
+        v_r  = (int) (vfr * magn);
+        v_g  = (int) (vfg * magn);
+        v_b  = (int) (vfb * magn);
+    }
+
+    /* Pick colors at extreme points */
+    mind = maxd = block[0] * v_r + block[1] * v_g + block[2] * v_b;
+    minp = maxp = block;
+    for (y = 0; y < 4; y++) {
+        for (x = 0; x < 4; x++) {
+            int dot = block[x * 4 + y * stride + 0] * v_r +
+                      block[x * 4 + y * stride + 1] * v_g +
+                      block[x * 4 + y * stride + 2] * v_b;
+
+            if (dot < mind) {
+                mind = dot;
+                minp = block + x * 4 + y * stride;
+            } else if (dot > maxd) {
+                maxd = dot;
+                maxp = block + x * 4 + y * stride;
+            }
+        }
+    }
+
+    *pmax16 = rgb2rgb565(maxp[0], maxp[1], maxp[2]);
+    *pmin16 = rgb2rgb565(minp[0], minp[1], minp[2]);
+}
+
+/* Try to optimize colors to suit block contents better, by solving
+ * a least squares system via normal equations + Cramer's rule. */
+static int refine_colors(const uint8_t *block, ptrdiff_t stride,
+                         uint16_t *pmax16, uint16_t *pmin16, uint32_t mask)
+{
+    uint32_t cm = mask;
+    uint16_t oldMin = *pmin16;
+    uint16_t oldMax = *pmax16;
+    uint16_t min16, max16;
+    int x, y;
+
+    /* Additional magic to save a lot of multiplies in the accumulating loop.
+     * The tables contain precomputed products of weights for least squares
+     * system, accumulated inside one 32-bit register */
+    const int w1tab[4] = { 3, 0, 2, 1 };
+    const int prods[4] = { 0x090000, 0x000900, 0x040102, 0x010402 };
+
+    /* Check if all pixels have the same index */
+    if (mask ^ (mask << 2) < 4) {
+        /* If so, linear system would be singular; solve using optimal
+         * single-color match on average color. */
+        int r = 8, g = 8, b = 8;
+        for (y = 0; y < 4; y++) {
+            for (x = 0; x < 4; x++) {
+                r += block[0 + x * 4 + y * stride];
+                g += block[1 + x * 4 + y * stride];
+                b += block[2 + x * 4 + y * stride];
+            }
+        }
+
+        r >>= 4;
+        g >>= 4;
+        b >>= 4;
+
+        max16 = (match5[r][0] << 11) | (match6[g][0] << 5) | match5[b][0];
+        min16 = (match5[r][1] << 11) | (match6[g][1] << 5) | match5[b][1];
+    } else {
+        float fr, fg, fb;
+        int at1_r = 0, at1_g = 0, at1_b = 0;
+        int at2_r = 0, at2_g = 0, at2_b = 0;
+        int akku = 0;
+        int xx, xy, yy;
+
+        for (y = 0; y < 4; y++) {
+            for (x = 0; x < 4; x++) {
+                int step = cm & 3;
+                int w1 = w1tab[step];
+                int r = block[0 + x * 4 + y * stride];
+                int g = block[1 + x * 4 + y * stride];
+                int b = block[2 + x * 4 + y * stride];
+
+                akku  += prods[step];
+                at1_r += w1 * r;
+                at1_g += w1 * g;
+                at1_b += w1 * b;
+                at2_r += r;
+                at2_g += g;
+                at2_b += b;
+
+                cm >>= 2;
+            }
+        }
+
+        at2_r = 3 * at2_r - at1_r;
+        at2_g = 3 * at2_g - at1_g;
+        at2_b = 3 * at2_b - at1_b;
+
+        /* Extract solutions and decide solvability */
+        xx =  akku >> 16;
+        yy = (akku >>  8) & 0xFF;
+        xy = (akku >>  0) & 0xFF;
+
+        fr = 3.0f * 31.0f / 255.0f / (xx * yy - xy * xy);
+        fg = fr * 63.0f / 31.0f;
+        fb = fr;
+
+        /* Solve */
+        max16  = av_clip_uintp2((at1_r * yy - at2_r * xy) * fr + 0.5f, 5) << 11;
+        max16 |= av_clip_uintp2((at1_g * yy - at2_g * xy) * fg + 0.5f, 6) <<  5;
+        max16 |= av_clip_uintp2((at1_b * yy - at2_b * xy) * fb + 0.5f, 5) <<  0;
+
+        min16  = av_clip_uintp2((at2_r * xx - at1_r * xy) * fr + 0.5f, 5) << 11;
+        min16 |= av_clip_uintp2((at2_g * xx - at1_g * xy) * fg + 0.5f, 6) <<  5;
+        min16 |= av_clip_uintp2((at2_b * xx - at1_b * xy) * fb + 0.5f, 5) <<  0;
+    }
+
+    *pmin16 = min16;
+    *pmax16 = max16;
+    return oldMin != min16 || oldMax != max16;
+}
+
+/* Check if input block is a constant color */
+static int constant_color(const uint8_t *block, ptrdiff_t stride)
+{
+    int x, y;
+    uint32_t first = AV_RL32(block);
+
+    for (y = 0; y < 4; y++)
+        for (x = 0; x < 4; x++)
+            if (first != AV_RL32(block + x * 4 + y * stride))
+                return 0;
+    return 1;
+}
+
+/* Main color compression function */
+static void compress_color(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
+{
+    uint32_t mask;
+    uint16_t max16, min16;
+    int constant = constant_color(block, stride);
+
+    /* Constant color will load values from tables */
+    if (constant) {
+        int r = block[0];
+        int g = block[1];
+        int b = block[2];
+        mask  = 0xAAAAAAAA;
+        max16 = (match5[r][0] << 11) | (match6[g][0] << 5) | match5[b][0];
+        min16 = (match5[r][1] << 11) | (match6[g][1] << 5) | match5[b][1];
+    } else {
+        int refine;
+
+        /* Otherwise find pca and map along principal axis */
+        optimize_colors(block, stride, &max16, &min16);
+        if (max16 != min16)
+            mask = match_colors(block, stride, max16, min16);
+        else
+            mask = 0;
+
+        /* One pass refinement */
+        refine  = refine_colors(block, stride, &max16, &min16, mask);
+        if (refine) {
+            if (max16 != min16)
+                mask = match_colors(block, stride, max16, min16);
+            else
+                mask = 0;
+        }
+    }
+
+    /* Finally write the color block */
+    if (max16 < min16) {
+        FFSWAP(uint16_t, min16, max16);
+        mask ^= 0x55555555;
+    }
+
+    AV_WL16(dst + 0, max16);
+    AV_WL16(dst + 2, min16);
+    AV_WL32(dst + 4, mask);
+}
+
+/* Alpha compression function */
+static void compress_alpha(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
+{
+    int x, y;
+    int dist, bias, dist4, dist2;
+    int mn, mx;
+    int bits = 0;
+    int mask = 0;
+
+    memset(dst, 0, 8);
+
+    /* Find min/max color */
+    mn = mx = block[3];
+    for (y = 0; y < 4; y++) {
+        for (x = 0; x < 4; x++) {
+            int val = block[3 + x * 4 + y * stride];
+            if (val < mn)
+                mn = val;
+            else if (val > mx)
+                mx = val;
+        }
+    }
+
+    /* Encode them */
+    dst[0] = (uint8_t) mx;
+    dst[1] = (uint8_t) mn;
+    dst += 2;
+
+    /* Mono-alpha shortcut */
+    if (mn == mx)
+        return;
+
+    /* Determine bias and emit color indices.
+     * Given the choice of mx/mn, these indices are optimal:
+     * fgiesen.wordpress.com/2009/12/15/dxt5-alpha-block-index-determination */
+    dist = mx - mn;
+
+    dist4 = dist * 4;
+    dist2 = dist * 2;
+    if (dist < 8)
+        bias = dist - 1 - mn * 7;
+    else
+        bias = dist / 2 + 2 - mn * 7;
+
+    for (y = 0; y < 4; y++) {
+        for (x = 0; x < 4; x++) {
+            int alp = block[3 + x * 4 + y * stride] * 7 + bias;
+            int ind, tmp;
+
+            /* This is a "linear scale" lerp factor between 0 (val=min)
+             * and 7 (val=max) to select index. */
+            tmp  = (alp >= dist4) ? -1 : 0;
+            ind  = tmp & 4;
+            alp -= dist4 & tmp;
+            tmp  = (alp >= dist2) ? -1 : 0;
+            ind += tmp & 2;
+            alp -= dist2 & tmp;
+            ind += (alp >= dist);
+
+            /* Turn linear scale into DXT index (0/1 are extreme points) */
+            ind  = -ind & 7;
+            ind ^= (2 > ind);
+
+            /* Write index */
+            mask |= ind << bits;
+            bits += 3;
+            if (bits >= 8) {
+                *dst++ = mask;
+                mask >>= 8;
+                bits  -= 8;
+            }
+        }
+    }
+}
+
+/**
+ * Convert a RGBA buffer to unscaled YCoCg.
+ * Scale is usually introduced to avoid banding over a certain range of colors,
+ * but this version of the algorithm does not introduce it as much as other
+ * implementations, allowing for a simpler and faster conversion.
+ */
+static void rgba2ycocg(uint8_t *dst, const uint8_t *pixel)
+{
+    int r =  pixel[0];
+    int g = (pixel[1] + 1) >> 1;
+    int b =  pixel[2];
+    int t = (2 + r + b) >> 2;
+
+    int y  = av_clip_uint8(g + t);
+    int co = av_clip_uint8(128 + ((r - b + 1) >> 1));
+    int cg = av_clip_uint8(128 + g - t);
+
+    dst[0] = (uint8_t) co;
+    dst[1] = (uint8_t) cg;
+    dst[2] = 0;
+    dst[3] = (uint8_t) y;
+}
+
+/**
+ * Compress one block of RGBA pixels in a DXT1 texture and store the
+ * resulting bytes in 'dst'. Alpha is not preserved.
+ *
+ * @param dst    output buffer.
+ * @param stride scanline in bytes.
+ * @param block  block to compress.
+ * @return how much texture data has been written.
+ */
+static int dxt1_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
+{
+    compress_color(dst, stride, block);
+
+    return 8;
+}
+
+/**
+ * Compress one block of RGBA pixels in a DXT5 texture and store the
+ * resulting bytes in 'dst'. Alpha is preserved.
+ *
+ * @param dst    output buffer.
+ * @param stride scanline in bytes.
+ * @param block  block to compress.
+ * @return how much texture data has been written.
+ */
+static int dxt5_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
+{
+    compress_alpha(dst, stride, block);
+    compress_color(dst + 8, stride, block);
+
+    return 16;
+}
+
+/**
+ * Compress one block of RGBA pixels in a DXT5-YCoCg texture and store the
+ * resulting bytes in 'dst'. Alpha is not preserved.
+ *
+ * @param dst    output buffer.
+ * @param stride scanline in bytes.
+ * @param block  block to compress.
+ * @return how much texture data has been written.
+ */
+static int dxt5ys_block(uint8_t *dst, ptrdiff_t stride, const uint8_t *block)
+{
+    int x, y;
+    uint8_t reorder[64];
+
+    /* Reorder the components and then run a normal DXT5 compression. */
+    for (y = 0; y < 4; y++)
+        for (x = 0; x < 4; x++)
+            rgba2ycocg(reorder + x * 4 + y * 16, block + x * 4 + y * stride);
+
+    compress_alpha(dst + 0, 16, reorder);
+    compress_color(dst + 8, 16, reorder);
+
+    return 16;
+}
+
+av_cold void ff_texturedspenc_init(TextureDSPContext *c)
+{
+    c->dxt1_block   = dxt1_block;
+    c->dxt5_block   = dxt5_block;
+    c->dxt5ys_block = dxt5ys_block;
+}