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Diffstat (limited to 'externals/stb/stb_dxt.cpp')
| -rw-r--r-- | externals/stb/stb_dxt.cpp | 765 |
1 files changed, 765 insertions, 0 deletions
diff --git a/externals/stb/stb_dxt.cpp b/externals/stb/stb_dxt.cpp new file mode 100644 index 000000000..64f1f3d03 --- /dev/null +++ b/externals/stb/stb_dxt.cpp @@ -0,0 +1,765 @@ +// SPDX-FileCopyrightText: fabian "ryg" giesen +// SPDX-License-Identifier: MIT + +// stb_dxt.h - v1.12 - DXT1/DXT5 compressor + +#include <stb_dxt.h> + +#include <stdlib.h> +#include <string.h> + +#if !defined(STBD_FABS) +#include <math.h> +#endif + +#ifndef STBD_FABS +#define STBD_FABS(x) fabs(x) +#endif + +static const unsigned char stb__OMatch5[256][2] = { + {0, 0}, {0, 0}, {0, 1}, {0, 1}, {1, 0}, {1, 0}, {1, 0}, {1, 1}, {1, 1}, + {1, 1}, {1, 2}, {0, 4}, {2, 1}, {2, 1}, {2, 1}, {2, 2}, {2, 2}, {2, 2}, + {2, 3}, {1, 5}, {3, 2}, {3, 2}, {4, 0}, {3, 3}, {3, 3}, {3, 3}, {3, 4}, + {3, 4}, {3, 4}, {3, 5}, {4, 3}, {4, 3}, {5, 2}, {4, 4}, {4, 4}, {4, 5}, + {4, 5}, {5, 4}, {5, 4}, {5, 4}, {6, 3}, {5, 5}, {5, 5}, {5, 6}, {4, 8}, + {6, 5}, {6, 5}, {6, 5}, {6, 6}, {6, 6}, {6, 6}, {6, 7}, {5, 9}, {7, 6}, + {7, 6}, {8, 4}, {7, 7}, {7, 7}, {7, 7}, {7, 8}, {7, 8}, {7, 8}, {7, 9}, + {8, 7}, {8, 7}, {9, 6}, {8, 8}, {8, 8}, {8, 9}, {8, 9}, {9, 8}, {9, 8}, + {9, 8}, {10, 7}, {9, 9}, {9, 9}, {9, 10}, {8, 12}, {10, 9}, {10, 9}, {10, 9}, + {10, 10}, {10, 10}, {10, 10}, {10, 11}, {9, 13}, {11, 10}, {11, 10}, {12, 8}, {11, 11}, + {11, 11}, {11, 11}, {11, 12}, {11, 12}, {11, 12}, {11, 13}, {12, 11}, {12, 11}, {13, 10}, + {12, 12}, {12, 12}, {12, 13}, {12, 13}, {13, 12}, {13, 12}, {13, 12}, {14, 11}, {13, 13}, + {13, 13}, {13, 14}, {12, 16}, {14, 13}, {14, 13}, {14, 13}, {14, 14}, {14, 14}, {14, 14}, + {14, 15}, {13, 17}, {15, 14}, {15, 14}, {16, 12}, {15, 15}, {15, 15}, {15, 15}, {15, 16}, + {15, 16}, {15, 16}, {15, 17}, {16, 15}, {16, 15}, {17, 14}, {16, 16}, {16, 16}, {16, 17}, + {16, 17}, {17, 16}, {17, 16}, {17, 16}, {18, 15}, {17, 17}, {17, 17}, {17, 18}, {16, 20}, + {18, 17}, {18, 17}, {18, 17}, {18, 18}, {18, 18}, {18, 18}, {18, 19}, {17, 21}, {19, 18}, + {19, 18}, {20, 16}, {19, 19}, {19, 19}, {19, 19}, {19, 20}, {19, 20}, {19, 20}, {19, 21}, + {20, 19}, {20, 19}, {21, 18}, {20, 20}, {20, 20}, {20, 21}, {20, 21}, {21, 20}, {21, 20}, + {21, 20}, {22, 19}, {21, 21}, {21, 21}, {21, 22}, {20, 24}, {22, 21}, {22, 21}, {22, 21}, + {22, 22}, {22, 22}, {22, 22}, {22, 23}, {21, 25}, {23, 22}, {23, 22}, {24, 20}, {23, 23}, + {23, 23}, {23, 23}, {23, 24}, {23, 24}, {23, 24}, {23, 25}, {24, 23}, {24, 23}, {25, 22}, + {24, 24}, {24, 24}, {24, 25}, {24, 25}, {25, 24}, {25, 24}, {25, 24}, {26, 23}, {25, 25}, + {25, 25}, {25, 26}, {24, 28}, {26, 25}, {26, 25}, {26, 25}, {26, 26}, {26, 26}, {26, 26}, + {26, 27}, {25, 29}, {27, 26}, {27, 26}, {28, 24}, {27, 27}, {27, 27}, {27, 27}, {27, 28}, + {27, 28}, {27, 28}, {27, 29}, {28, 27}, {28, 27}, {29, 26}, {28, 28}, {28, 28}, {28, 29}, + {28, 29}, {29, 28}, {29, 28}, {29, 28}, {30, 27}, {29, 29}, {29, 29}, {29, 30}, {29, 30}, + {30, 29}, {30, 29}, {30, 29}, {30, 30}, {30, 30}, {30, 30}, {30, 31}, {30, 31}, {31, 30}, + {31, 30}, {31, 30}, {31, 31}, {31, 31}, +}; +static const unsigned char stb__OMatch6[256][2] = { + {0, 0}, {0, 1}, {1, 0}, {1, 1}, {1, 1}, {1, 2}, {2, 1}, {2, 2}, {2, 2}, + {2, 3}, {3, 2}, {3, 3}, {3, 3}, {3, 4}, {4, 3}, {4, 4}, {4, 4}, {4, 5}, + {5, 4}, {5, 5}, {5, 5}, {5, 6}, {6, 5}, {6, 6}, {6, 6}, {6, 7}, {7, 6}, + {7, 7}, {7, 7}, {7, 8}, {8, 7}, {8, 8}, {8, 8}, {8, 9}, {9, 8}, {9, 9}, + {9, 9}, {9, 10}, {10, 9}, {10, 10}, {10, 10}, {10, 11}, {11, 10}, {8, 16}, {11, 11}, + {11, 12}, {12, 11}, {9, 17}, {12, 12}, {12, 13}, {13, 12}, {11, 16}, {13, 13}, {13, 14}, + {14, 13}, {12, 17}, {14, 14}, {14, 15}, {15, 14}, {14, 16}, {15, 15}, {15, 16}, {16, 14}, + {16, 15}, {17, 14}, {16, 16}, {16, 17}, {17, 16}, {18, 15}, {17, 17}, {17, 18}, {18, 17}, + {20, 14}, {18, 18}, {18, 19}, {19, 18}, {21, 15}, {19, 19}, {19, 20}, {20, 19}, {20, 20}, + {20, 20}, {20, 21}, {21, 20}, {21, 21}, {21, 21}, {21, 22}, {22, 21}, {22, 22}, {22, 22}, + {22, 23}, {23, 22}, {23, 23}, {23, 23}, {23, 24}, {24, 23}, {24, 24}, {24, 24}, {24, 25}, + {25, 24}, {25, 25}, {25, 25}, {25, 26}, {26, 25}, {26, 26}, {26, 26}, {26, 27}, {27, 26}, + {24, 32}, {27, 27}, {27, 28}, {28, 27}, {25, 33}, {28, 28}, {28, 29}, {29, 28}, {27, 32}, + {29, 29}, {29, 30}, {30, 29}, {28, 33}, {30, 30}, {30, 31}, {31, 30}, {30, 32}, {31, 31}, + {31, 32}, {32, 30}, {32, 31}, {33, 30}, {32, 32}, {32, 33}, {33, 32}, {34, 31}, {33, 33}, + {33, 34}, {34, 33}, {36, 30}, {34, 34}, {34, 35}, {35, 34}, {37, 31}, {35, 35}, {35, 36}, + {36, 35}, {36, 36}, {36, 36}, {36, 37}, {37, 36}, {37, 37}, {37, 37}, {37, 38}, {38, 37}, + {38, 38}, {38, 38}, {38, 39}, {39, 38}, {39, 39}, {39, 39}, {39, 40}, {40, 39}, {40, 40}, + {40, 40}, {40, 41}, {41, 40}, {41, 41}, {41, 41}, {41, 42}, {42, 41}, {42, 42}, {42, 42}, + {42, 43}, {43, 42}, {40, 48}, {43, 43}, {43, 44}, {44, 43}, {41, 49}, {44, 44}, {44, 45}, + {45, 44}, {43, 48}, {45, 45}, {45, 46}, {46, 45}, {44, 49}, {46, 46}, {46, 47}, {47, 46}, + {46, 48}, {47, 47}, {47, 48}, {48, 46}, {48, 47}, {49, 46}, {48, 48}, {48, 49}, {49, 48}, + {50, 47}, {49, 49}, {49, 50}, {50, 49}, {52, 46}, {50, 50}, {50, 51}, {51, 50}, {53, 47}, + {51, 51}, {51, 52}, {52, 51}, {52, 52}, {52, 52}, {52, 53}, {53, 52}, {53, 53}, {53, 53}, + {53, 54}, {54, 53}, {54, 54}, {54, 54}, {54, 55}, {55, 54}, {55, 55}, {55, 55}, {55, 56}, + {56, 55}, {56, 56}, {56, 56}, {56, 57}, {57, 56}, {57, 57}, {57, 57}, {57, 58}, {58, 57}, + {58, 58}, {58, 58}, {58, 59}, {59, 58}, {59, 59}, {59, 59}, {59, 60}, {60, 59}, {60, 60}, + {60, 60}, {60, 61}, {61, 60}, {61, 61}, {61, 61}, {61, 62}, {62, 61}, {62, 62}, {62, 62}, + {62, 63}, {63, 62}, {63, 63}, {63, 63}, +}; + +static int stb__Mul8Bit(int a, int b) { + int t = a * b + 128; + return (t + (t >> 8)) >> 8; +} + +static void stb__From16Bit(unsigned char* out, unsigned short v) { + int rv = (v & 0xf800) >> 11; + int gv = (v & 0x07e0) >> 5; + int bv = (v & 0x001f) >> 0; + + // expand to 8 bits via bit replication + out[0] = static_cast<unsigned char>((rv * 33) >> 2); + out[1] = static_cast<unsigned char>((gv * 65) >> 4); + out[2] = static_cast<unsigned char>((bv * 33) >> 2); + out[3] = 0; +} + +static unsigned short stb__As16Bit(int r, int g, int b) { + return (unsigned short)((stb__Mul8Bit(r, 31) << 11) + (stb__Mul8Bit(g, 63) << 5) + + stb__Mul8Bit(b, 31)); +} + +// linear interpolation at 1/3 point between a and b, using desired rounding +// type +static int stb__Lerp13(int a, int b) { +#ifdef STB_DXT_USE_ROUNDING_BIAS + // with rounding bias + return a + stb__Mul8Bit(b - a, 0x55); +#else + // without rounding bias + // replace "/ 3" by "* 0xaaab) >> 17" if your compiler sucks or you really + // need every ounce of speed. + return (2 * a + b) / 3; +#endif +} + +// linear interpolation at 1/2 point between a and b +static int stb__Lerp12(int a, int b) { + return (a + b) / 2; +} + +// lerp RGB color +static void stb__Lerp13RGB(unsigned char* out, unsigned char* p1, unsigned char* p2) { + out[0] = (unsigned char)stb__Lerp13(p1[0], p2[0]); + out[1] = (unsigned char)stb__Lerp13(p1[1], p2[1]); + out[2] = (unsigned char)stb__Lerp13(p1[2], p2[2]); +} + +static void stb__Lerp12RGB(unsigned char* out, unsigned char* p1, unsigned char* p2) { + out[0] = (unsigned char)stb__Lerp12(p1[0], p2[0]); + out[1] = (unsigned char)stb__Lerp12(p1[1], p2[1]); + out[2] = (unsigned char)stb__Lerp12(p1[2], p2[2]); +} + +/****************************************************************************/ + +static void stb__Eval4Colors(unsigned char* color, unsigned short c0, unsigned short c1) { + stb__From16Bit(color + 0, c0); + stb__From16Bit(color + 4, c1); + stb__Lerp13RGB(color + 8, color + 0, color + 4); + stb__Lerp13RGB(color + 12, color + 4, color + 0); +} + +static void stb__Eval3Colors(unsigned char* color, unsigned short c0, unsigned short c1) { + stb__From16Bit(color + 0, c0); + stb__From16Bit(color + 4, c1); + stb__Lerp12RGB(color + 8, color + 0, color + 4); +} + +// The color matching function +static unsigned int stb__MatchColorsBlock(unsigned char* block, unsigned char* color) { + unsigned int mask = 0; + int dirr = color[0 * 4 + 0] - color[1 * 4 + 0]; + int dirg = color[0 * 4 + 1] - color[1 * 4 + 1]; + int dirb = color[0 * 4 + 2] - color[1 * 4 + 2]; + int dots[16]; + int stops[4]; + int i; + int c0Point, halfPoint, c3Point; + + for (i = 0; i < 16; i++) + dots[i] = block[i * 4 + 0] * dirr + block[i * 4 + 1] * dirg + block[i * 4 + 2] * dirb; + + for (i = 0; i < 4; i++) + stops[i] = color[i * 4 + 0] * dirr + color[i * 4 + 1] * dirg + color[i * 4 + 2] * 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 + + c0Point = (stops[1] + stops[3]); + halfPoint = (stops[3] + stops[2]); + c3Point = (stops[2] + stops[0]); + + for (i = 15; i >= 0; i--) { + int dot = dots[i] * 2; + mask <<= 2; + + if (dot < halfPoint) + mask |= (dot < c0Point) ? 1 : 3; + else + mask |= (dot < c3Point) ? 2 : 0; + } + + return mask; +} + +static unsigned int stb__MatchColorsAlphaBlock(unsigned char* block, unsigned char* color) { + unsigned int mask = 0; + int dirr = color[0 * 4 + 0] - color[1 * 4 + 0]; + int dirg = color[0 * 4 + 1] - color[1 * 4 + 1]; + int dirb = color[0 * 4 + 2] - color[1 * 4 + 2]; + int dots[16]; + int stops[3]; + int i; + int c0Point, c2Point; + + for (i = 0; i < 16; i++) + dots[i] = block[i * 4 + 0] * dirr + block[i * 4 + 1] * dirg + block[i * 4 + 2] * dirb; + + for (i = 0; i < 3; i++) + stops[i] = color[i * 4 + 0] * dirr + color[i * 4 + 1] * dirg + color[i * 4 + 2] * dirb; + + c0Point = (stops[1] + stops[2]); + c2Point = (stops[2] + stops[0]); + + for (i = 15; i >= 0; i--) { + int dot = dots[i] * 2; + mask <<= 2; + + if (block[i * 4 + 3] == 0) + mask |= 3; + else if (dot < c2Point) + mask |= (dot < c0Point) ? 0 : 2; + else + mask |= (dot < c0Point) ? 1 : 0; + } + + return mask; +} + +static void stb__ReorderColors(unsigned short* pmax16, unsigned short* pmin16) { + if (*pmin16 < *pmax16) { + unsigned short t = *pmin16; + *pmin16 = *pmax16; + *pmax16 = t; + } +} + +static void stb__FinalizeColors(unsigned short* pmax16, unsigned short* pmin16, + unsigned int* pmask) { + if (*pmax16 < *pmin16) { + unsigned short t = *pmin16; + *pmin16 = *pmax16; + *pmax16 = t; + *pmask ^= 0x55555555; + } +} + +// The color optimization function. (Clever code, part 1) +static void stb__OptimizeColorsBlock(unsigned char* block, unsigned short* pmax16, + unsigned short* pmin16) { + int mind, maxd; + unsigned char *minp, *maxp; + double magn; + int v_r, v_g, v_b; + static const int nIterPower = 4; + float covf[6], vfr, vfg, vfb; + + // determine color distribution + int cov[6]; + int mu[3], min[3], max[3]; + int ch, i, iter; + + for (ch = 0; ch < 3; ch++) { + const unsigned char* bp = ((const unsigned char*)block) + ch; + int muv, minv, maxv; + + muv = minv = maxv = bp[0]; + for (i = 4; i < 64; i += 4) { + muv += bp[i]; + if (bp[i] < minv) + minv = bp[i]; + else if (bp[i] > maxv) + maxv = bp[i]; + } + + mu[ch] = (muv + 8) >> 4; + min[ch] = minv; + max[ch] = maxv; + } + + // determine covariance matrix + for (i = 0; i < 6; i++) + cov[i] = 0; + + for (i = 0; i < 16; i++) { + int r = block[i * 4 + 0] - mu[0]; + int g = block[i * 4 + 1] - mu[1]; + int b = block[i * 4 + 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 (i = 0; i < 6; i++) + covf[i] = static_cast<float>(cov[i]) / 255.0f; + + vfr = (float)(max[0] - min[0]); + vfg = (float)(max[1] - min[1]); + vfb = (float)(max[2] - min[2]); + + for (iter = 0; iter < nIterPower; 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 = STBD_FABS(vfr); + if (STBD_FABS(vfg) > magn) + magn = STBD_FABS(vfg); + if (STBD_FABS(vfb) > magn) + magn = STBD_FABS(vfb); + + if (magn < 4.0f) { // too small, default to luminance + v_r = 299; // JPEG YCbCr luma coefs, scaled by 1000. + 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); + } + + minp = maxp = block; + mind = maxd = block[0] * v_r + block[1] * v_g + block[2] * v_b; + // Pick colors at extreme points + for (i = 1; i < 16; i++) { + int dot = block[i * 4 + 0] * v_r + block[i * 4 + 1] * v_g + block[i * 4 + 2] * v_b; + + if (dot < mind) { + mind = dot; + minp = block + i * 4; + } + + if (dot > maxd) { + maxd = dot; + maxp = block + i * 4; + } + } + + *pmax16 = stb__As16Bit(maxp[0], maxp[1], maxp[2]); + *pmin16 = stb__As16Bit(minp[0], minp[1], minp[2]); + stb__ReorderColors(pmax16, pmin16); +} + +static void stb__OptimizeColorsAlphaBlock(unsigned char* block, unsigned short* pmax16, + unsigned short* pmin16) { + int mind, maxd; + unsigned char *minp, *maxp; + double magn; + int v_r, v_g, v_b; + static const int nIterPower = 4; + float covf[6], vfr, vfg, vfb; + + // determine color distribution + int cov[6]; + int mu[3], min[3], max[3]; + int ch, i, iter; + + for (ch = 0; ch < 3; ch++) { + const unsigned char* bp = ((const unsigned char*)block) + ch; + int muv = 0, minv = 256, maxv = -1; + int num = 0; + + for (i = 0; i < 64; i += 4) { + if (bp[3 - ch] == 0) { + continue; + } + + muv += bp[i]; + if (bp[i] < minv) + minv = bp[i]; + else if (bp[i] > maxv) + maxv = bp[i]; + + num++; + } + + mu[ch] = num > 0 ? (muv + 8) / num : 0; + min[ch] = minv; + max[ch] = maxv; + } + + // determine covariance matrix + for (i = 0; i < 6; i++) + cov[i] = 0; + + for (i = 0; i < 16; i++) { + if (block[i * 4 + 3] == 0) { + continue; + } + + int r = block[i * 4 + 0] - mu[0]; + int g = block[i * 4 + 1] - mu[1]; + int b = block[i * 4 + 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 (i = 0; i < 6; i++) + covf[i] = static_cast<float>(cov[i]) / 255.0f; + + vfr = (float)(max[0] - min[0]); + vfg = (float)(max[1] - min[1]); + vfb = (float)(max[2] - min[2]); + + for (iter = 0; iter < nIterPower; 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 = STBD_FABS(vfr); + if (STBD_FABS(vfg) > magn) + magn = STBD_FABS(vfg); + if (STBD_FABS(vfb) > magn) + magn = STBD_FABS(vfb); + + if (magn < 4.0f) { // too small, default to luminance + v_r = 299; // JPEG YCbCr luma coefs, scaled by 1000. + 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); + } + + minp = maxp = NULL; + mind = 0x7fffffff; + maxd = -0x80000000; + + // Pick colors at extreme points + for (i = 0; i < 16; i++) { + if (block[i * 4 + 3] == 0) { + continue; + } + + int dot = block[i * 4 + 0] * v_r + block[i * 4 + 1] * v_g + block[i * 4 + 2] * v_b; + + if (dot < mind) { + mind = dot; + minp = block + i * 4; + } + + if (dot > maxd) { + maxd = dot; + maxp = block + i * 4; + } + } + + if (!maxp) { + // all alpha, no color + *pmin16 = 0xffff; + *pmax16 = 0; + } else { + // endpoint colors found + *pmax16 = stb__As16Bit(maxp[0], maxp[1], maxp[2]); + *pmin16 = stb__As16Bit(minp[0], minp[1], minp[2]); + + if (*pmax16 == *pmin16) { + // modify the endpoints to indicate presence of an alpha block + if (*pmax16 > 0) { + (*pmax16)--; + } else { + (*pmin16)++; + } + } + + stb__ReorderColors(pmax16, pmin16); + } +} + +static const float stb__midpoints5[32] = { + 0.015686f, 0.047059f, 0.078431f, 0.111765f, 0.145098f, 0.176471f, 0.207843f, 0.241176f, + 0.274510f, 0.305882f, 0.337255f, 0.370588f, 0.403922f, 0.435294f, 0.466667f, 0.5f, + 0.533333f, 0.564706f, 0.596078f, 0.629412f, 0.662745f, 0.694118f, 0.725490f, 0.758824f, + 0.792157f, 0.823529f, 0.854902f, 0.888235f, 0.921569f, 0.952941f, 0.984314f, 1.0f}; + +static const float stb__midpoints6[64] = { + 0.007843f, 0.023529f, 0.039216f, 0.054902f, 0.070588f, 0.086275f, 0.101961f, 0.117647f, + 0.133333f, 0.149020f, 0.164706f, 0.180392f, 0.196078f, 0.211765f, 0.227451f, 0.245098f, + 0.262745f, 0.278431f, 0.294118f, 0.309804f, 0.325490f, 0.341176f, 0.356863f, 0.372549f, + 0.388235f, 0.403922f, 0.419608f, 0.435294f, 0.450980f, 0.466667f, 0.482353f, 0.500000f, + 0.517647f, 0.533333f, 0.549020f, 0.564706f, 0.580392f, 0.596078f, 0.611765f, 0.627451f, + 0.643137f, 0.658824f, 0.674510f, 0.690196f, 0.705882f, 0.721569f, 0.737255f, 0.754902f, + 0.772549f, 0.788235f, 0.803922f, 0.819608f, 0.835294f, 0.850980f, 0.866667f, 0.882353f, + 0.898039f, 0.913725f, 0.929412f, 0.945098f, 0.960784f, 0.976471f, 0.992157f, 1.0f}; + +static unsigned short stb__Quantize5(float x) { + unsigned short q; + x = x < 0 ? 0 : x > 1 ? 1 : x; // saturate + q = (unsigned short)(x * 31); + q += (x > stb__midpoints5[q]); + return q; +} + +static unsigned short stb__Quantize6(float x) { + unsigned short q; + x = x < 0 ? 0 : x > 1 ? 1 : x; // saturate + q = (unsigned short)(x * 63); + q += (x > stb__midpoints6[q]); + return q; +} + +// The refinement function. (Clever code, part 2) +// Tries to optimize colors to suit block contents better. +// (By solving a least squares system via normal equations+Cramer's rule) +static int stb__RefineBlock(unsigned char* block, unsigned short* pmax16, unsigned short* pmin16, + unsigned int mask) { + static const int w1Tab[4] = {3, 0, 2, 1}; + static const int prods[4] = {0x090000, 0x000900, 0x040102, 0x010402}; + // ^some magic to save a lot of multiplies in the accumulating loop... + // (precomputed products of weights for least squares system, accumulated + // inside one 32-bit register) + + float f; + unsigned short oldMin, oldMax, min16, max16; + int i, akku = 0, xx, xy, yy; + int At1_r, At1_g, At1_b; + int At2_r, At2_g, At2_b; + unsigned int cm = mask; + + oldMin = *pmin16; + oldMax = *pmax16; + + if ((mask ^ (mask << 2)) < 4) // all pixels have the same index? + { + // yes, linear system would be singular; solve using optimal + // single-color match on average color + int r = 8, g = 8, b = 8; + for (i = 0; i < 16; ++i) { + r += block[i * 4 + 0]; + g += block[i * 4 + 1]; + b += block[i * 4 + 2]; + } + + r >>= 4; + g >>= 4; + b >>= 4; + + max16 = static_cast<unsigned short>((stb__OMatch5[r][0] << 11) | (stb__OMatch6[g][0] << 5) | + stb__OMatch5[b][0]); + min16 = static_cast<unsigned short>((stb__OMatch5[r][1] << 11) | (stb__OMatch6[g][1] << 5) | + stb__OMatch5[b][1]); + } else { + At1_r = At1_g = At1_b = 0; + At2_r = At2_g = At2_b = 0; + for (i = 0; i < 16; ++i, cm >>= 2) { + int step = cm & 3; + int w1 = w1Tab[step]; + int r = block[i * 4 + 0]; + int g = block[i * 4 + 1]; + int b = block[i * 4 + 2]; + + akku += prods[step]; + At1_r += w1 * r; + At1_g += w1 * g; + At1_b += w1 * b; + At2_r += r; + At2_g += g; + At2_b += b; + } + + 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; + + f = 3.0f / 255.0f / static_cast<float>(xx * yy - xy * xy); + + max16 = static_cast<unsigned short>( + stb__Quantize5(static_cast<float>(At1_r * yy - At2_r * xy) * f) << 11); + max16 |= static_cast<unsigned short>( + stb__Quantize6(static_cast<float>(At1_g * yy - At2_g * xy) * f) << 5); + max16 |= static_cast<unsigned short>( + stb__Quantize5(static_cast<float>(At1_b * yy - At2_b * xy) * f) << 0); + + min16 = static_cast<unsigned short>( + stb__Quantize5(static_cast<float>(At2_r * xx - At1_r * xy) * f) << 11); + min16 |= static_cast<unsigned short>( + stb__Quantize6(static_cast<float>(At2_g * xx - At1_g * xy) * f) << 5); + min16 |= static_cast<unsigned short>( + stb__Quantize5(static_cast<float>(At2_b * xx - At1_b * xy) * f) << 0); + } + + *pmin16 = min16; + *pmax16 = max16; + stb__ReorderColors(pmax16, pmin16); + + return oldMin != min16 || oldMax != max16; +} + +// Color block compression +static void stb__CompressColorBlock(unsigned char* dest, unsigned char* block, int alpha, + int mode) { + unsigned int mask; + int i; + int refinecount; + unsigned short max16, min16; + unsigned char color[4 * 4]; + + refinecount = (mode & STB_DXT_HIGHQUAL) ? 2 : 1; + + // check if block is constant + for (i = 1; i < 16; i++) + if (((unsigned int*)block)[i] != ((unsigned int*)block)[0]) + break; + + if (i == 16 && block[3] == 0 && alpha) { // constant alpha + mask = 0xffffffff; + max16 = 0; + min16 = 0xffff; + } else if (i == 16) { // constant color + int r = block[0], g = block[1], b = block[2]; + mask = 0xaaaaaaaa; + max16 = static_cast<unsigned short>((stb__OMatch5[r][0] << 11) | (stb__OMatch6[g][0] << 5) | + stb__OMatch5[b][0]); + min16 = static_cast<unsigned short>((stb__OMatch5[r][1] << 11) | (stb__OMatch6[g][1] << 5) | + stb__OMatch5[b][1]); + } else if (alpha) { + stb__OptimizeColorsAlphaBlock(block, &max16, &min16); + stb__Eval3Colors(color, max16, min16); + mask = stb__MatchColorsAlphaBlock(block, color); + } else { + // first step: PCA+map along principal axis + stb__OptimizeColorsBlock(block, &max16, &min16); + if (max16 != min16) { + stb__Eval4Colors(color, max16, min16); + mask = stb__MatchColorsBlock(block, color); + } else + mask = 0; + + // third step: refine (multiple times if requested) + for (i = 0; i < refinecount; i++) { + unsigned int lastmask = mask; + + if (stb__RefineBlock(block, &max16, &min16, mask)) { + if (max16 != min16) { + stb__Eval4Colors(color, max16, min16); + mask = stb__MatchColorsBlock(block, color); + } else { + mask = 0; + break; + } + } + + if (mask == lastmask) + break; + } + } + + // write the color block + if (!alpha) + stb__FinalizeColors(&max16, &min16, &mask); + + dest[0] = (unsigned char)(max16); + dest[1] = (unsigned char)(max16 >> 8); + dest[2] = (unsigned char)(min16); + dest[3] = (unsigned char)(min16 >> 8); + dest[4] = (unsigned char)(mask); + dest[5] = (unsigned char)(mask >> 8); + dest[6] = (unsigned char)(mask >> 16); + dest[7] = (unsigned char)(mask >> 24); +} + +// Alpha block compression (this is easy for a change) +static void stb__CompressAlphaBlock(unsigned char* dest, unsigned char* src, int stride) { + int i, dist, bias, dist4, dist2, bits, mask; + + // find min/max color + int mn, mx; + mn = mx = src[0]; + + for (i = 1; i < 16; i++) { + if (src[i * stride] < mn) + mn = src[i * stride]; + else if (src[i * stride] > mx) + mx = src[i * stride]; + } + + // encode them + dest[0] = (unsigned char)mx; + dest[1] = (unsigned char)mn; + dest += 2; + + // determine bias and emit color indices + // given the choice of mx/mn, these indices are optimal: + // http://fgiesen.wordpress.com/2009/12/15/dxt5-alpha-block-index-determination/ + dist = mx - mn; + dist4 = dist * 4; + dist2 = dist * 2; + bias = (dist < 8) ? (dist - 1) : (dist / 2 + 2); + bias -= mn * 7; + bits = 0, mask = 0; + + for (i = 0; i < 16; i++) { + int a = src[i * stride] * 7 + bias; + int ind, t; + + // select index. this is a "linear scale" lerp factor between 0 (val=min) + // and 7 (val=max). + t = (a >= dist4) ? -1 : 0; + ind = t & 4; + a -= dist4 & t; + t = (a >= dist2) ? -1 : 0; + ind += t & 2; + a -= dist2 & t; + ind += (a >= dist); + + // turn linear scale into DXT index (0/1 are extremal pts) + ind = -ind & 7; + ind ^= (2 > ind); + + // write index + mask |= ind << bits; + if ((bits += 3) >= 8) { + *dest++ = (unsigned char)mask; + mask >>= 8; + bits -= 8; + } + } +} + +void stb_compress_bc1_block(unsigned char* dest, const unsigned char* src, int alpha, int mode) { + stb__CompressColorBlock(dest, (unsigned char*)src, alpha, mode); +} + +void stb_compress_bc3_block(unsigned char* dest, const unsigned char* src, int mode) { + unsigned char data[16][4]; + int i; + + stb__CompressAlphaBlock(dest, (unsigned char*)src + 3, 4); + dest += 8; + // make a new copy of the data in which alpha is opaque, + // because code uses a fast test for color constancy + memcpy(data, src, 4 * 16); + for (i = 0; i < 16; ++i) + data[i][3] = 255; + src = &data[0][0]; + + stb__CompressColorBlock(dest, (unsigned char*)src, 0, mode); +} |