765 lines
27 KiB
C++
765 lines
27 KiB
C++
// SPDX-FileCopyrightText: fabian "ryg" giesen
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// SPDX-License-Identifier: MIT
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// stb_dxt.h - v1.12 - DXT1/DXT5 compressor
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#include <stb_dxt.h>
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#include <stdlib.h>
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#include <string.h>
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#if !defined(STBD_FABS)
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#include <math.h>
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#endif
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#ifndef STBD_FABS
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#define STBD_FABS(x) fabs(x)
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#endif
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static const unsigned char stb__OMatch5[256][2] = {
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{0, 0}, {0, 0}, {0, 1}, {0, 1}, {1, 0}, {1, 0}, {1, 0}, {1, 1}, {1, 1},
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{1, 1}, {1, 2}, {0, 4}, {2, 1}, {2, 1}, {2, 1}, {2, 2}, {2, 2}, {2, 2},
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{2, 3}, {1, 5}, {3, 2}, {3, 2}, {4, 0}, {3, 3}, {3, 3}, {3, 3}, {3, 4},
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{3, 4}, {3, 4}, {3, 5}, {4, 3}, {4, 3}, {5, 2}, {4, 4}, {4, 4}, {4, 5},
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{4, 5}, {5, 4}, {5, 4}, {5, 4}, {6, 3}, {5, 5}, {5, 5}, {5, 6}, {4, 8},
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{6, 5}, {6, 5}, {6, 5}, {6, 6}, {6, 6}, {6, 6}, {6, 7}, {5, 9}, {7, 6},
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{7, 6}, {8, 4}, {7, 7}, {7, 7}, {7, 7}, {7, 8}, {7, 8}, {7, 8}, {7, 9},
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{8, 7}, {8, 7}, {9, 6}, {8, 8}, {8, 8}, {8, 9}, {8, 9}, {9, 8}, {9, 8},
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{9, 8}, {10, 7}, {9, 9}, {9, 9}, {9, 10}, {8, 12}, {10, 9}, {10, 9}, {10, 9},
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{10, 10}, {10, 10}, {10, 10}, {10, 11}, {9, 13}, {11, 10}, {11, 10}, {12, 8}, {11, 11},
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{11, 11}, {11, 11}, {11, 12}, {11, 12}, {11, 12}, {11, 13}, {12, 11}, {12, 11}, {13, 10},
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{12, 12}, {12, 12}, {12, 13}, {12, 13}, {13, 12}, {13, 12}, {13, 12}, {14, 11}, {13, 13},
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{13, 13}, {13, 14}, {12, 16}, {14, 13}, {14, 13}, {14, 13}, {14, 14}, {14, 14}, {14, 14},
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{14, 15}, {13, 17}, {15, 14}, {15, 14}, {16, 12}, {15, 15}, {15, 15}, {15, 15}, {15, 16},
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{15, 16}, {15, 16}, {15, 17}, {16, 15}, {16, 15}, {17, 14}, {16, 16}, {16, 16}, {16, 17},
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{16, 17}, {17, 16}, {17, 16}, {17, 16}, {18, 15}, {17, 17}, {17, 17}, {17, 18}, {16, 20},
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{18, 17}, {18, 17}, {18, 17}, {18, 18}, {18, 18}, {18, 18}, {18, 19}, {17, 21}, {19, 18},
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{19, 18}, {20, 16}, {19, 19}, {19, 19}, {19, 19}, {19, 20}, {19, 20}, {19, 20}, {19, 21},
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{20, 19}, {20, 19}, {21, 18}, {20, 20}, {20, 20}, {20, 21}, {20, 21}, {21, 20}, {21, 20},
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{21, 20}, {22, 19}, {21, 21}, {21, 21}, {21, 22}, {20, 24}, {22, 21}, {22, 21}, {22, 21},
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{22, 22}, {22, 22}, {22, 22}, {22, 23}, {21, 25}, {23, 22}, {23, 22}, {24, 20}, {23, 23},
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{23, 23}, {23, 23}, {23, 24}, {23, 24}, {23, 24}, {23, 25}, {24, 23}, {24, 23}, {25, 22},
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{24, 24}, {24, 24}, {24, 25}, {24, 25}, {25, 24}, {25, 24}, {25, 24}, {26, 23}, {25, 25},
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{25, 25}, {25, 26}, {24, 28}, {26, 25}, {26, 25}, {26, 25}, {26, 26}, {26, 26}, {26, 26},
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{26, 27}, {25, 29}, {27, 26}, {27, 26}, {28, 24}, {27, 27}, {27, 27}, {27, 27}, {27, 28},
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{27, 28}, {27, 28}, {27, 29}, {28, 27}, {28, 27}, {29, 26}, {28, 28}, {28, 28}, {28, 29},
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{28, 29}, {29, 28}, {29, 28}, {29, 28}, {30, 27}, {29, 29}, {29, 29}, {29, 30}, {29, 30},
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{30, 29}, {30, 29}, {30, 29}, {30, 30}, {30, 30}, {30, 30}, {30, 31}, {30, 31}, {31, 30},
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{31, 30}, {31, 30}, {31, 31}, {31, 31},
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};
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static const unsigned char stb__OMatch6[256][2] = {
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{0, 0}, {0, 1}, {1, 0}, {1, 1}, {1, 1}, {1, 2}, {2, 1}, {2, 2}, {2, 2},
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{2, 3}, {3, 2}, {3, 3}, {3, 3}, {3, 4}, {4, 3}, {4, 4}, {4, 4}, {4, 5},
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{5, 4}, {5, 5}, {5, 5}, {5, 6}, {6, 5}, {6, 6}, {6, 6}, {6, 7}, {7, 6},
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{7, 7}, {7, 7}, {7, 8}, {8, 7}, {8, 8}, {8, 8}, {8, 9}, {9, 8}, {9, 9},
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{9, 9}, {9, 10}, {10, 9}, {10, 10}, {10, 10}, {10, 11}, {11, 10}, {8, 16}, {11, 11},
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{11, 12}, {12, 11}, {9, 17}, {12, 12}, {12, 13}, {13, 12}, {11, 16}, {13, 13}, {13, 14},
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{14, 13}, {12, 17}, {14, 14}, {14, 15}, {15, 14}, {14, 16}, {15, 15}, {15, 16}, {16, 14},
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{16, 15}, {17, 14}, {16, 16}, {16, 17}, {17, 16}, {18, 15}, {17, 17}, {17, 18}, {18, 17},
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{20, 14}, {18, 18}, {18, 19}, {19, 18}, {21, 15}, {19, 19}, {19, 20}, {20, 19}, {20, 20},
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{20, 20}, {20, 21}, {21, 20}, {21, 21}, {21, 21}, {21, 22}, {22, 21}, {22, 22}, {22, 22},
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{22, 23}, {23, 22}, {23, 23}, {23, 23}, {23, 24}, {24, 23}, {24, 24}, {24, 24}, {24, 25},
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{25, 24}, {25, 25}, {25, 25}, {25, 26}, {26, 25}, {26, 26}, {26, 26}, {26, 27}, {27, 26},
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{24, 32}, {27, 27}, {27, 28}, {28, 27}, {25, 33}, {28, 28}, {28, 29}, {29, 28}, {27, 32},
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{29, 29}, {29, 30}, {30, 29}, {28, 33}, {30, 30}, {30, 31}, {31, 30}, {30, 32}, {31, 31},
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{31, 32}, {32, 30}, {32, 31}, {33, 30}, {32, 32}, {32, 33}, {33, 32}, {34, 31}, {33, 33},
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{33, 34}, {34, 33}, {36, 30}, {34, 34}, {34, 35}, {35, 34}, {37, 31}, {35, 35}, {35, 36},
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{36, 35}, {36, 36}, {36, 36}, {36, 37}, {37, 36}, {37, 37}, {37, 37}, {37, 38}, {38, 37},
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{38, 38}, {38, 38}, {38, 39}, {39, 38}, {39, 39}, {39, 39}, {39, 40}, {40, 39}, {40, 40},
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{40, 40}, {40, 41}, {41, 40}, {41, 41}, {41, 41}, {41, 42}, {42, 41}, {42, 42}, {42, 42},
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{42, 43}, {43, 42}, {40, 48}, {43, 43}, {43, 44}, {44, 43}, {41, 49}, {44, 44}, {44, 45},
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{45, 44}, {43, 48}, {45, 45}, {45, 46}, {46, 45}, {44, 49}, {46, 46}, {46, 47}, {47, 46},
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{46, 48}, {47, 47}, {47, 48}, {48, 46}, {48, 47}, {49, 46}, {48, 48}, {48, 49}, {49, 48},
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{50, 47}, {49, 49}, {49, 50}, {50, 49}, {52, 46}, {50, 50}, {50, 51}, {51, 50}, {53, 47},
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{51, 51}, {51, 52}, {52, 51}, {52, 52}, {52, 52}, {52, 53}, {53, 52}, {53, 53}, {53, 53},
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{53, 54}, {54, 53}, {54, 54}, {54, 54}, {54, 55}, {55, 54}, {55, 55}, {55, 55}, {55, 56},
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{56, 55}, {56, 56}, {56, 56}, {56, 57}, {57, 56}, {57, 57}, {57, 57}, {57, 58}, {58, 57},
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{58, 58}, {58, 58}, {58, 59}, {59, 58}, {59, 59}, {59, 59}, {59, 60}, {60, 59}, {60, 60},
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{60, 60}, {60, 61}, {61, 60}, {61, 61}, {61, 61}, {61, 62}, {62, 61}, {62, 62}, {62, 62},
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{62, 63}, {63, 62}, {63, 63}, {63, 63},
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};
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static int stb__Mul8Bit(int a, int b) {
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int t = a * b + 128;
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return (t + (t >> 8)) >> 8;
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}
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static void stb__From16Bit(unsigned char* out, unsigned short v) {
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int rv = (v & 0xf800) >> 11;
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int gv = (v & 0x07e0) >> 5;
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int bv = (v & 0x001f) >> 0;
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// expand to 8 bits via bit replication
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out[0] = static_cast<unsigned char>((rv * 33) >> 2);
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out[1] = static_cast<unsigned char>((gv * 65) >> 4);
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out[2] = static_cast<unsigned char>((bv * 33) >> 2);
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out[3] = 0;
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}
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static unsigned short stb__As16Bit(int r, int g, int b) {
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return (unsigned short)((stb__Mul8Bit(r, 31) << 11) + (stb__Mul8Bit(g, 63) << 5) +
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stb__Mul8Bit(b, 31));
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}
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// linear interpolation at 1/3 point between a and b, using desired rounding
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// type
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static int stb__Lerp13(int a, int b) {
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#ifdef STB_DXT_USE_ROUNDING_BIAS
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// with rounding bias
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return a + stb__Mul8Bit(b - a, 0x55);
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#else
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// without rounding bias
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// replace "/ 3" by "* 0xaaab) >> 17" if your compiler sucks or you really
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// need every ounce of speed.
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return (2 * a + b) / 3;
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#endif
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}
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// linear interpolation at 1/2 point between a and b
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static int stb__Lerp12(int a, int b) {
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return (a + b) / 2;
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}
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// lerp RGB color
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static void stb__Lerp13RGB(unsigned char* out, unsigned char* p1, unsigned char* p2) {
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out[0] = (unsigned char)stb__Lerp13(p1[0], p2[0]);
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out[1] = (unsigned char)stb__Lerp13(p1[1], p2[1]);
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out[2] = (unsigned char)stb__Lerp13(p1[2], p2[2]);
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}
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static void stb__Lerp12RGB(unsigned char* out, unsigned char* p1, unsigned char* p2) {
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out[0] = (unsigned char)stb__Lerp12(p1[0], p2[0]);
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out[1] = (unsigned char)stb__Lerp12(p1[1], p2[1]);
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out[2] = (unsigned char)stb__Lerp12(p1[2], p2[2]);
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}
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/****************************************************************************/
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static void stb__Eval4Colors(unsigned char* color, unsigned short c0, unsigned short c1) {
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stb__From16Bit(color + 0, c0);
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stb__From16Bit(color + 4, c1);
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stb__Lerp13RGB(color + 8, color + 0, color + 4);
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stb__Lerp13RGB(color + 12, color + 4, color + 0);
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}
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static void stb__Eval3Colors(unsigned char* color, unsigned short c0, unsigned short c1) {
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stb__From16Bit(color + 0, c0);
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stb__From16Bit(color + 4, c1);
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stb__Lerp12RGB(color + 8, color + 0, color + 4);
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}
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// The color matching function
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static unsigned int stb__MatchColorsBlock(unsigned char* block, unsigned char* color) {
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unsigned int mask = 0;
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int dirr = color[0 * 4 + 0] - color[1 * 4 + 0];
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int dirg = color[0 * 4 + 1] - color[1 * 4 + 1];
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int dirb = color[0 * 4 + 2] - color[1 * 4 + 2];
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int dots[16];
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int stops[4];
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int i;
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int c0Point, halfPoint, c3Point;
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for (i = 0; i < 16; i++)
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dots[i] = block[i * 4 + 0] * dirr + block[i * 4 + 1] * dirg + block[i * 4 + 2] * dirb;
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for (i = 0; i < 4; i++)
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stops[i] = color[i * 4 + 0] * dirr + color[i * 4 + 1] * dirg + color[i * 4 + 2] * dirb;
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// think of the colors as arranged on a line; project point onto that line,
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// then choose next color out of available ones. we compute the crossover
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// points for "best color in top half"/"best in bottom half" and then the same
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// inside that subinterval.
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//
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// relying on this 1d approximation isn't always optimal in terms of euclidean
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// distance, but it's very close and a lot faster.
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// http://cbloomrants.blogspot.com/2008/12/12-08-08-dxtc-summary.html
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c0Point = (stops[1] + stops[3]);
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halfPoint = (stops[3] + stops[2]);
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c3Point = (stops[2] + stops[0]);
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for (i = 15; i >= 0; i--) {
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int dot = dots[i] * 2;
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mask <<= 2;
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if (dot < halfPoint)
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mask |= (dot < c0Point) ? 1 : 3;
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else
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mask |= (dot < c3Point) ? 2 : 0;
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}
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return mask;
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}
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static unsigned int stb__MatchColorsAlphaBlock(unsigned char* block, unsigned char* color) {
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unsigned int mask = 0;
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int dirr = color[0 * 4 + 0] - color[1 * 4 + 0];
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int dirg = color[0 * 4 + 1] - color[1 * 4 + 1];
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int dirb = color[0 * 4 + 2] - color[1 * 4 + 2];
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int dots[16];
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int stops[3];
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int i;
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int c0Point, c2Point;
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for (i = 0; i < 16; i++)
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dots[i] = block[i * 4 + 0] * dirr + block[i * 4 + 1] * dirg + block[i * 4 + 2] * dirb;
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for (i = 0; i < 3; i++)
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stops[i] = color[i * 4 + 0] * dirr + color[i * 4 + 1] * dirg + color[i * 4 + 2] * dirb;
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c0Point = (stops[1] + stops[2]);
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c2Point = (stops[2] + stops[0]);
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for (i = 15; i >= 0; i--) {
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int dot = dots[i] * 2;
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mask <<= 2;
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if (block[i * 4 + 3] == 0)
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mask |= 3;
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else if (dot < c2Point)
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mask |= (dot < c0Point) ? 0 : 2;
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else
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mask |= (dot < c0Point) ? 1 : 0;
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}
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return mask;
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}
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static void stb__ReorderColors(unsigned short* pmax16, unsigned short* pmin16) {
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if (*pmin16 < *pmax16) {
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unsigned short t = *pmin16;
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*pmin16 = *pmax16;
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*pmax16 = t;
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}
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}
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static void stb__FinalizeColors(unsigned short* pmax16, unsigned short* pmin16,
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unsigned int* pmask) {
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if (*pmax16 < *pmin16) {
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unsigned short t = *pmin16;
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*pmin16 = *pmax16;
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*pmax16 = t;
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*pmask ^= 0x55555555;
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}
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}
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// The color optimization function. (Clever code, part 1)
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static void stb__OptimizeColorsBlock(unsigned char* block, unsigned short* pmax16,
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unsigned short* pmin16) {
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int mind, maxd;
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unsigned char *minp, *maxp;
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double magn;
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int v_r, v_g, v_b;
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static const int nIterPower = 4;
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float covf[6], vfr, vfg, vfb;
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// determine color distribution
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int cov[6];
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int mu[3], min[3], max[3];
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int ch, i, iter;
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for (ch = 0; ch < 3; ch++) {
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const unsigned char* bp = ((const unsigned char*)block) + ch;
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int muv, minv, maxv;
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muv = minv = maxv = bp[0];
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for (i = 4; i < 64; i += 4) {
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muv += bp[i];
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if (bp[i] < minv)
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minv = bp[i];
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else if (bp[i] > maxv)
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maxv = bp[i];
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}
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mu[ch] = (muv + 8) >> 4;
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min[ch] = minv;
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max[ch] = maxv;
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}
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// determine covariance matrix
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for (i = 0; i < 6; i++)
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cov[i] = 0;
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for (i = 0; i < 16; i++) {
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int r = block[i * 4 + 0] - mu[0];
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int g = block[i * 4 + 1] - mu[1];
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int b = block[i * 4 + 2] - mu[2];
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cov[0] += r * r;
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cov[1] += r * g;
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cov[2] += r * b;
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cov[3] += g * g;
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cov[4] += g * b;
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cov[5] += b * b;
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}
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// convert covariance matrix to float, find principal axis via power iter
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for (i = 0; i < 6; i++)
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covf[i] = static_cast<float>(cov[i]) / 255.0f;
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vfr = (float)(max[0] - min[0]);
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vfg = (float)(max[1] - min[1]);
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vfb = (float)(max[2] - min[2]);
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for (iter = 0; iter < nIterPower; iter++) {
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float r = vfr * covf[0] + vfg * covf[1] + vfb * covf[2];
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float g = vfr * covf[1] + vfg * covf[3] + vfb * covf[4];
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float b = vfr * covf[2] + vfg * covf[4] + vfb * covf[5];
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vfr = r;
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vfg = g;
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vfb = b;
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}
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magn = STBD_FABS(vfr);
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if (STBD_FABS(vfg) > magn)
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magn = STBD_FABS(vfg);
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if (STBD_FABS(vfb) > magn)
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magn = STBD_FABS(vfb);
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if (magn < 4.0f) { // too small, default to luminance
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v_r = 299; // JPEG YCbCr luma coefs, scaled by 1000.
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v_g = 587;
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v_b = 114;
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} else {
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magn = 512.0 / magn;
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v_r = (int)(vfr * magn);
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v_g = (int)(vfg * magn);
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v_b = (int)(vfb * magn);
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}
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minp = maxp = block;
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mind = maxd = block[0] * v_r + block[1] * v_g + block[2] * v_b;
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// Pick colors at extreme points
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for (i = 1; i < 16; i++) {
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int dot = block[i * 4 + 0] * v_r + block[i * 4 + 1] * v_g + block[i * 4 + 2] * v_b;
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if (dot < mind) {
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mind = dot;
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minp = block + i * 4;
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}
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if (dot > maxd) {
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maxd = dot;
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maxp = block + i * 4;
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}
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}
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*pmax16 = stb__As16Bit(maxp[0], maxp[1], maxp[2]);
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*pmin16 = stb__As16Bit(minp[0], minp[1], minp[2]);
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stb__ReorderColors(pmax16, pmin16);
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}
|
|
|
|
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);
|
|
}
|