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720 lines
28 KiB
C
720 lines
28 KiB
C
// stb_dxt.h - v1.12 - DXT1/DXT5 compressor - public domain
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// original by fabian "ryg" giesen - ported to C by stb
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// use '#define STB_DXT_IMPLEMENTATION' before including to create the implementation
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//
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// USAGE:
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// call stb_compress_dxt_block() for every block (you must pad)
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// source should be a 4x4 block of RGBA data in row-major order;
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// Alpha channel is not stored if you specify alpha=0 (but you
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// must supply some constant alpha in the alpha channel).
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// You can turn on dithering and "high quality" using mode.
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//
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// version history:
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// v1.12 - (ryg) fix bug in single-color table generator
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// v1.11 - (ryg) avoid racy global init, better single-color tables, remove dither
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// v1.10 - (i.c) various small quality improvements
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// v1.09 - (stb) update documentation re: surprising alpha channel requirement
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// v1.08 - (stb) fix bug in dxt-with-alpha block
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// v1.07 - (stb) bc4; allow not using libc; add STB_DXT_STATIC
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// v1.06 - (stb) fix to known-broken 1.05
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// v1.05 - (stb) support bc5/3dc (Arvids Kokins), use extern "C" in C++ (Pavel Krajcevski)
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// v1.04 - (ryg) default to no rounding bias for lerped colors (as per S3TC/DX10 spec);
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// single color match fix (allow for inexact color interpolation);
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// optimal DXT5 index finder; "high quality" mode that runs multiple refinement steps.
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// v1.03 - (stb) endianness support
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// v1.02 - (stb) fix alpha encoding bug
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// v1.01 - (stb) fix bug converting to RGB that messed up quality, thanks ryg & cbloom
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// v1.00 - (stb) first release
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//
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// contributors:
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// Rich Geldreich (more accurate index selection)
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// Kevin Schmidt (#defines for "freestanding" compilation)
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// github:ppiastucki (BC4 support)
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// Ignacio Castano - improve DXT endpoint quantization
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// Alan Hickman - static table initialization
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//
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// LICENSE
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//
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// See end of file for license information.
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#ifndef STB_INCLUDE_STB_DXT_H
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#define STB_INCLUDE_STB_DXT_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifdef STB_DXT_STATIC
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#define STBDDEF static
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#else
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#define STBDDEF extern
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#endif
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// compression mode (bitflags)
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#define STB_DXT_NORMAL 0
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#define STB_DXT_DITHER 1 // use dithering. was always dubious, now deprecated. does nothing!
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#define STB_DXT_HIGHQUAL 2 // high quality mode, does two refinement steps instead of 1. ~30-40% slower.
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STBDDEF void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src_rgba_four_bytes_per_pixel, int alpha, int mode);
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STBDDEF void stb_compress_bc4_block(unsigned char *dest, const unsigned char *src_r_one_byte_per_pixel);
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STBDDEF void stb_compress_bc5_block(unsigned char *dest, const unsigned char *src_rg_two_byte_per_pixel);
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#define STB_COMPRESS_DXT_BLOCK
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#ifdef __cplusplus
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}
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#endif
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#endif // STB_INCLUDE_STB_DXT_H
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#ifdef STB_DXT_IMPLEMENTATION
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// configuration options for DXT encoder. set them in the project/makefile or just define
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// them at the top.
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// STB_DXT_USE_ROUNDING_BIAS
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// use a rounding bias during color interpolation. this is closer to what "ideal"
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// interpolation would do but doesn't match the S3TC/DX10 spec. old versions (pre-1.03)
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// implicitly had this turned on.
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//
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// in case you're targeting a specific type of hardware (e.g. console programmers):
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// NVidia and Intel GPUs (as of 2010) as well as DX9 ref use DXT decoders that are closer
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// to STB_DXT_USE_ROUNDING_BIAS. AMD/ATI, S3 and DX10 ref are closer to rounding with no bias.
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// you also see "(a*5 + b*3) / 8" on some old GPU designs.
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// #define STB_DXT_USE_ROUNDING_BIAS
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#include <stdlib.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 },
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{ 1, 1 }, { 1, 1 }, { 1, 2 }, { 0, 4 }, { 2, 1 }, { 2, 1 }, { 2, 1 }, { 2, 2 },
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{ 2, 2 }, { 2, 2 }, { 2, 3 }, { 1, 5 }, { 3, 2 }, { 3, 2 }, { 4, 0 }, { 3, 3 },
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{ 3, 3 }, { 3, 3 }, { 3, 4 }, { 3, 4 }, { 3, 4 }, { 3, 5 }, { 4, 3 }, { 4, 3 },
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{ 5, 2 }, { 4, 4 }, { 4, 4 }, { 4, 5 }, { 4, 5 }, { 5, 4 }, { 5, 4 }, { 5, 4 },
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{ 6, 3 }, { 5, 5 }, { 5, 5 }, { 5, 6 }, { 4, 8 }, { 6, 5 }, { 6, 5 }, { 6, 5 },
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{ 6, 6 }, { 6, 6 }, { 6, 6 }, { 6, 7 }, { 5, 9 }, { 7, 6 }, { 7, 6 }, { 8, 4 },
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{ 7, 7 }, { 7, 7 }, { 7, 7 }, { 7, 8 }, { 7, 8 }, { 7, 8 }, { 7, 9 }, { 8, 7 },
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{ 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 },
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{ 10, 9 }, { 10, 10 }, { 10, 10 }, { 10, 10 }, { 10, 11 }, { 9, 13 }, { 11, 10 }, { 11, 10 },
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{ 12, 8 }, { 11, 11 }, { 11, 11 }, { 11, 11 }, { 11, 12 }, { 11, 12 }, { 11, 12 }, { 11, 13 },
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{ 12, 11 }, { 12, 11 }, { 13, 10 }, { 12, 12 }, { 12, 12 }, { 12, 13 }, { 12, 13 }, { 13, 12 },
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{ 13, 12 }, { 13, 12 }, { 14, 11 }, { 13, 13 }, { 13, 13 }, { 13, 14 }, { 12, 16 }, { 14, 13 },
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{ 14, 13 }, { 14, 13 }, { 14, 14 }, { 14, 14 }, { 14, 14 }, { 14, 15 }, { 13, 17 }, { 15, 14 },
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{ 15, 14 }, { 16, 12 }, { 15, 15 }, { 15, 15 }, { 15, 15 }, { 15, 16 }, { 15, 16 }, { 15, 16 },
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{ 15, 17 }, { 16, 15 }, { 16, 15 }, { 17, 14 }, { 16, 16 }, { 16, 16 }, { 16, 17 }, { 16, 17 },
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{ 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 },
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{ 19, 18 }, { 19, 18 }, { 20, 16 }, { 19, 19 }, { 19, 19 }, { 19, 19 }, { 19, 20 }, { 19, 20 },
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{ 19, 20 }, { 19, 21 }, { 20, 19 }, { 20, 19 }, { 21, 18 }, { 20, 20 }, { 20, 20 }, { 20, 21 },
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{ 20, 21 }, { 21, 20 }, { 21, 20 }, { 21, 20 }, { 22, 19 }, { 21, 21 }, { 21, 21 }, { 21, 22 },
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{ 20, 24 }, { 22, 21 }, { 22, 21 }, { 22, 21 }, { 22, 22 }, { 22, 22 }, { 22, 22 }, { 22, 23 },
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{ 21, 25 }, { 23, 22 }, { 23, 22 }, { 24, 20 }, { 23, 23 }, { 23, 23 }, { 23, 23 }, { 23, 24 },
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{ 23, 24 }, { 23, 24 }, { 23, 25 }, { 24, 23 }, { 24, 23 }, { 25, 22 }, { 24, 24 }, { 24, 24 },
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{ 24, 25 }, { 24, 25 }, { 25, 24 }, { 25, 24 }, { 25, 24 }, { 26, 23 }, { 25, 25 }, { 25, 25 },
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{ 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 },
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{ 27, 28 }, { 27, 28 }, { 27, 28 }, { 27, 29 }, { 28, 27 }, { 28, 27 }, { 29, 26 }, { 28, 28 },
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{ 28, 28 }, { 28, 29 }, { 28, 29 }, { 29, 28 }, { 29, 28 }, { 29, 28 }, { 30, 27 }, { 29, 29 },
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{ 29, 29 }, { 29, 30 }, { 29, 30 }, { 30, 29 }, { 30, 29 }, { 30, 29 }, { 30, 30 }, { 30, 30 },
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{ 30, 30 }, { 30, 31 }, { 30, 31 }, { 31, 30 }, { 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 },
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{ 2, 2 }, { 2, 3 }, { 3, 2 }, { 3, 3 }, { 3, 3 }, { 3, 4 }, { 4, 3 }, { 4, 4 },
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{ 4, 4 }, { 4, 5 }, { 5, 4 }, { 5, 5 }, { 5, 5 }, { 5, 6 }, { 6, 5 }, { 6, 6 },
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{ 6, 6 }, { 6, 7 }, { 7, 6 }, { 7, 7 }, { 7, 7 }, { 7, 8 }, { 8, 7 }, { 8, 8 },
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{ 8, 8 }, { 8, 9 }, { 9, 8 }, { 9, 9 }, { 9, 9 }, { 9, 10 }, { 10, 9 }, { 10, 10 },
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{ 10, 10 }, { 10, 11 }, { 11, 10 }, { 8, 16 }, { 11, 11 }, { 11, 12 }, { 12, 11 }, { 9, 17 },
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{ 12, 12 }, { 12, 13 }, { 13, 12 }, { 11, 16 }, { 13, 13 }, { 13, 14 }, { 14, 13 }, { 12, 17 },
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{ 14, 14 }, { 14, 15 }, { 15, 14 }, { 14, 16 }, { 15, 15 }, { 15, 16 }, { 16, 14 }, { 16, 15 },
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{ 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 },
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{ 20, 20 }, { 20, 20 }, { 20, 21 }, { 21, 20 }, { 21, 21 }, { 21, 21 }, { 21, 22 }, { 22, 21 },
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{ 22, 22 }, { 22, 22 }, { 22, 23 }, { 23, 22 }, { 23, 23 }, { 23, 23 }, { 23, 24 }, { 24, 23 },
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{ 24, 24 }, { 24, 24 }, { 24, 25 }, { 25, 24 }, { 25, 25 }, { 25, 25 }, { 25, 26 }, { 26, 25 },
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{ 26, 26 }, { 26, 26 }, { 26, 27 }, { 27, 26 }, { 24, 32 }, { 27, 27 }, { 27, 28 }, { 28, 27 },
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{ 25, 33 }, { 28, 28 }, { 28, 29 }, { 29, 28 }, { 27, 32 }, { 29, 29 }, { 29, 30 }, { 30, 29 },
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{ 28, 33 }, { 30, 30 }, { 30, 31 }, { 31, 30 }, { 30, 32 }, { 31, 31 }, { 31, 32 }, { 32, 30 },
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{ 32, 31 }, { 33, 30 }, { 32, 32 }, { 32, 33 }, { 33, 32 }, { 34, 31 }, { 33, 33 }, { 33, 34 },
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{ 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 },
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{ 38, 37 }, { 38, 38 }, { 38, 38 }, { 38, 39 }, { 39, 38 }, { 39, 39 }, { 39, 39 }, { 39, 40 },
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{ 40, 39 }, { 40, 40 }, { 40, 40 }, { 40, 41 }, { 41, 40 }, { 41, 41 }, { 41, 41 }, { 41, 42 },
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{ 42, 41 }, { 42, 42 }, { 42, 42 }, { 42, 43 }, { 43, 42 }, { 40, 48 }, { 43, 43 }, { 43, 44 },
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{ 44, 43 }, { 41, 49 }, { 44, 44 }, { 44, 45 }, { 45, 44 }, { 43, 48 }, { 45, 45 }, { 45, 46 },
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{ 46, 45 }, { 44, 49 }, { 46, 46 }, { 46, 47 }, { 47, 46 }, { 46, 48 }, { 47, 47 }, { 47, 48 },
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{ 48, 46 }, { 48, 47 }, { 49, 46 }, { 48, 48 }, { 48, 49 }, { 49, 48 }, { 50, 47 }, { 49, 49 },
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{ 49, 50 }, { 50, 49 }, { 52, 46 }, { 50, 50 }, { 50, 51 }, { 51, 50 }, { 53, 47 }, { 51, 51 },
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{ 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 },
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{ 55, 56 }, { 56, 55 }, { 56, 56 }, { 56, 56 }, { 56, 57 }, { 57, 56 }, { 57, 57 }, { 57, 57 },
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{ 57, 58 }, { 58, 57 }, { 58, 58 }, { 58, 58 }, { 58, 59 }, { 59, 58 }, { 59, 59 }, { 59, 59 },
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{ 59, 60 }, { 60, 59 }, { 60, 60 }, { 60, 60 }, { 60, 61 }, { 61, 60 }, { 61, 61 }, { 61, 61 },
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{ 61, 62 }, { 62, 61 }, { 62, 62 }, { 62, 62 }, { 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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{
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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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{
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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] = (rv * 33) >> 2;
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out[1] = (gv * 65) >> 4;
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out[2] = (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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{
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return (unsigned short)((stb__Mul8Bit(r,31) << 11) + (stb__Mul8Bit(g,63) << 5) + 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 type
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static int stb__Lerp13(int a, int b)
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{
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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 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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// lerp RGB color
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static void stb__Lerp13RGB(unsigned char *out, unsigned char *p1, unsigned char *p2)
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{
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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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/****************************************************************************/
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static void stb__EvalColors(unsigned char *color,unsigned short c0,unsigned short c1)
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{
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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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// The color matching function
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static unsigned int stb__MatchColorsBlock(unsigned char *block, unsigned char *color)
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{
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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, then choose
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// next color out of available ones. we compute the crossover points for "best color in top
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// half"/"best in bottom half" and then the same inside that subinterval.
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//
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// relying on this 1d approximation isn't always optimal in terms of euclidean distance,
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// 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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// The color optimization function. (Clever code, part 1)
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static void stb__OptimizeColorsBlock(unsigned char *block, unsigned short *pmax16, unsigned short *pmin16)
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{
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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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{
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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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{
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muv += bp[i];
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if (bp[i] < minv) minv = bp[i];
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else if (bp[i] > maxv) 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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{
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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] = 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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{
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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) magn = STBD_FABS(vfg);
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if (STBD_FABS(vfb) > magn) 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);
|
|
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]);
|
|
}
|
|
|
|
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 = (stb__OMatch5[r][0]<<11) | (stb__OMatch6[g][0]<<5) | stb__OMatch5[b][0];
|
|
min16 = (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 / (xx*yy - xy*xy);
|
|
|
|
max16 = stb__Quantize5((At1_r*yy - At2_r * xy) * f) << 11;
|
|
max16 |= stb__Quantize6((At1_g*yy - At2_g * xy) * f) << 5;
|
|
max16 |= stb__Quantize5((At1_b*yy - At2_b * xy) * f) << 0;
|
|
|
|
min16 = stb__Quantize5((At2_r*xx - At1_r * xy) * f) << 11;
|
|
min16 |= stb__Quantize6((At2_g*xx - At1_g * xy) * f) << 5;
|
|
min16 |= stb__Quantize5((At2_b*xx - At1_b * xy) * f) << 0;
|
|
}
|
|
|
|
*pmin16 = min16;
|
|
*pmax16 = max16;
|
|
return oldMin != min16 || oldMax != max16;
|
|
}
|
|
|
|
// Color block compression
|
|
static void stb__CompressColorBlock(unsigned char *dest, unsigned char *block, 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) { // constant color
|
|
int r = block[0], g = block[1], b = block[2];
|
|
mask = 0xaaaaaaaa;
|
|
max16 = (stb__OMatch5[r][0]<<11) | (stb__OMatch6[g][0]<<5) | stb__OMatch5[b][0];
|
|
min16 = (stb__OMatch5[r][1]<<11) | (stb__OMatch6[g][1]<<5) | stb__OMatch5[b][1];
|
|
} else {
|
|
// first step: PCA+map along principal axis
|
|
stb__OptimizeColorsBlock(block,&max16,&min16);
|
|
if (max16 != min16) {
|
|
stb__EvalColors(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__EvalColors(color,max16,min16);
|
|
mask = stb__MatchColorsBlock(block,color);
|
|
} else {
|
|
mask = 0;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if(mask == lastmask)
|
|
break;
|
|
}
|
|
}
|
|
|
|
// write the color block
|
|
if(max16 < min16)
|
|
{
|
|
unsigned short t = min16;
|
|
min16 = max16;
|
|
max16 = t;
|
|
mask ^= 0x55555555;
|
|
}
|
|
|
|
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_dxt_block(unsigned char *dest, const unsigned char *src, int alpha, int mode)
|
|
{
|
|
unsigned char data[16][4];
|
|
if (alpha) {
|
|
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,mode);
|
|
}
|
|
|
|
void stb_compress_bc4_block(unsigned char *dest, const unsigned char *src)
|
|
{
|
|
stb__CompressAlphaBlock(dest,(unsigned char*) src, 1);
|
|
}
|
|
|
|
void stb_compress_bc5_block(unsigned char *dest, const unsigned char *src)
|
|
{
|
|
stb__CompressAlphaBlock(dest,(unsigned char*) src,2);
|
|
stb__CompressAlphaBlock(dest + 8,(unsigned char*) src+1,2);
|
|
}
|
|
#endif // STB_DXT_IMPLEMENTATION
|
|
|
|
// Compile with STB_DXT_IMPLEMENTATION and STB_DXT_GENERATE_TABLES
|
|
// defined to generate the tables above.
|
|
#ifdef STB_DXT_GENERATE_TABLES
|
|
#include <stdio.h>
|
|
|
|
int main()
|
|
{
|
|
int i, j;
|
|
const char *omatch_names[] = { "stb__OMatch5", "stb__OMatch6" };
|
|
int dequant_mults[2] = { 33*4, 65 }; // .4 fixed-point dequant multipliers
|
|
|
|
// optimal endpoint tables
|
|
for (i = 0; i < 2; ++i) {
|
|
int dequant = dequant_mults[i];
|
|
int size = i ? 64 : 32;
|
|
printf("static const unsigned char %s[256][2] = {\n", omatch_names[i]);
|
|
for (int j = 0; j < 256; ++j) {
|
|
int mn, mx;
|
|
int best_mn = 0, best_mx = 0;
|
|
int best_err = 256 * 100;
|
|
for (mn=0;mn<size;mn++) {
|
|
for (mx=0;mx<size;mx++) {
|
|
int mine = (mn * dequant) >> 4;
|
|
int maxe = (mx * dequant) >> 4;
|
|
int err = abs(stb__Lerp13(maxe, mine) - j) * 100;
|
|
|
|
// DX10 spec says that interpolation must be within 3% of "correct" result,
|
|
// add this as error term. Normally we'd expect a random distribution of
|
|
// +-1.5% error, but nowhere in the spec does it say that the error has to be
|
|
// unbiased - better safe than sorry.
|
|
err += abs(maxe - mine) * 3;
|
|
|
|
if(err < best_err) {
|
|
best_mn = mn;
|
|
best_mx = mx;
|
|
best_err = err;
|
|
}
|
|
}
|
|
}
|
|
if ((j % 8) == 0) printf(" "); // 2 spaces, third is done below
|
|
printf(" { %2d, %2d },", best_mx, best_mn);
|
|
if ((j % 8) == 7) printf("\n");
|
|
}
|
|
printf("};\n");
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
------------------------------------------------------------------------------
|
|
This software is available under 2 licenses -- choose whichever you prefer.
|
|
------------------------------------------------------------------------------
|
|
ALTERNATIVE A - MIT License
|
|
Copyright (c) 2017 Sean Barrett
|
|
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.
|
|
------------------------------------------------------------------------------
|
|
ALTERNATIVE B - Public Domain (www.unlicense.org)
|
|
This is free and unencumbered software released into the public domain.
|
|
Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
|
|
software, either in source code form or as a compiled binary, for any purpose,
|
|
commercial or non-commercial, and by any means.
|
|
In jurisdictions that recognize copyright laws, the author or authors of this
|
|
software dedicate any and all copyright interest in the software to the public
|
|
domain. We make this dedication for the benefit of the public at large and to
|
|
the detriment of our heirs and successors. We intend this dedication to be an
|
|
overt act of relinquishment in perpetuity of all present and future rights to
|
|
this software under copyright law.
|
|
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 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.
|
|
------------------------------------------------------------------------------
|
|
*/
|