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728 lines
23 KiB
728 lines
23 KiB
// stb_dxt.h - v1.08b - 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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// A is ignored if you specify alpha=0; you can turn on dithering
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// and "high quality" using mode.
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//
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// version history:
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// v1.08 - (sbt) 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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// Kevin Schmidt (#defines for "freestanding" compilation)
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// github:ppiastucki (BC4 support)
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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. dubious win. never use for normal maps and the like!
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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_ABS) || !defined(STBI_FABS)
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#include <math.h>
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#endif
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#ifndef STBD_ABS
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#define STBD_ABS(i) abs(i)
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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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#ifndef STBD_MEMSET
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#include <string.h>
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#define STBD_MEMSET memset
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#endif
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static unsigned char stb__Expand5[32];
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static unsigned char stb__Expand6[64];
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static unsigned char stb__OMatch5[256][2];
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static unsigned char stb__OMatch6[256][2];
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static unsigned char stb__QuantRBTab[256+16];
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static unsigned char stb__QuantGTab[256+16];
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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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out[0] = stb__Expand5[rv];
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out[1] = stb__Expand6[gv];
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out[2] = stb__Expand5[bv];
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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 (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] = stb__Lerp13(p1[0], p2[0]);
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out[1] = stb__Lerp13(p1[1], p2[1]);
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out[2] = stb__Lerp13(p1[2], p2[2]);
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}
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/****************************************************************************/
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// compute table to reproduce constant colors as accurately as possible
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static void stb__PrepareOptTable(unsigned char *Table,const unsigned char *expand,int size)
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{
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int i,mn,mx;
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for (i=0;i<256;i++) {
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int bestErr = 256;
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for (mn=0;mn<size;mn++) {
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for (mx=0;mx<size;mx++) {
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int mine = expand[mn];
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int maxe = expand[mx];
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int err = STBD_ABS(stb__Lerp13(maxe, mine) - i);
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// DX10 spec says that interpolation must be within 3% of "correct" result,
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// add this as error term. (normally we'd expect a random distribution of
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// +-1.5% error, but nowhere in the spec does it say that the error has to be
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// unbiased - better safe than sorry).
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err += STBD_ABS(maxe - mine) * 3 / 100;
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if(err < bestErr)
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{
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Table[i*2+0] = mx;
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Table[i*2+1] = mn;
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bestErr = err;
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}
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}
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}
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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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// Block dithering function. Simply dithers a block to 565 RGB.
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// (Floyd-Steinberg)
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static void stb__DitherBlock(unsigned char *dest, unsigned char *block)
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{
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int err[8],*ep1 = err,*ep2 = err+4, *et;
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int ch,y;
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// process channels seperately
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for (ch=0; ch<3; ++ch) {
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unsigned char *bp = block+ch, *dp = dest+ch;
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unsigned char *quant = (ch == 1) ? stb__QuantGTab+8 : stb__QuantRBTab+8;
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STBD_MEMSET(err, 0, sizeof(err));
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for(y=0; y<4; ++y) {
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dp[ 0] = quant[bp[ 0] + ((3*ep2[1] + 5*ep2[0]) >> 4)];
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ep1[0] = bp[ 0] - dp[ 0];
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dp[ 4] = quant[bp[ 4] + ((7*ep1[0] + 3*ep2[2] + 5*ep2[1] + ep2[0]) >> 4)];
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ep1[1] = bp[ 4] - dp[ 4];
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dp[ 8] = quant[bp[ 8] + ((7*ep1[1] + 3*ep2[3] + 5*ep2[2] + ep2[1]) >> 4)];
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ep1[2] = bp[ 8] - dp[ 8];
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dp[12] = quant[bp[12] + ((7*ep1[2] + 5*ep2[3] + ep2[2]) >> 4)];
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ep1[3] = bp[12] - dp[12];
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bp += 16;
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dp += 16;
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et = ep1, ep1 = ep2, ep2 = et; // swap
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}
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}
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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,int dither)
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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]) >> 1;
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halfPoint = (stops[3] + stops[2]) >> 1;
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c3Point = (stops[2] + stops[0]) >> 1;
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if(!dither) {
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// the version without dithering is straightforward
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for (i=15;i>=0;i--) {
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int dot = dots[i];
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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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} else {
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// with floyd-steinberg dithering
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int err[8],*ep1 = err,*ep2 = err+4;
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int *dp = dots, y;
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c0Point <<= 4;
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halfPoint <<= 4;
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c3Point <<= 4;
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for(i=0;i<8;i++)
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err[i] = 0;
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for(y=0;y<4;y++)
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{
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int dot,lmask,step;
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dot = (dp[0] << 4) + (3*ep2[1] + 5*ep2[0]);
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if(dot < halfPoint)
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step = (dot < c0Point) ? 1 : 3;
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else
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step = (dot < c3Point) ? 2 : 0;
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ep1[0] = dp[0] - stops[step];
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lmask = step;
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dot = (dp[1] << 4) + (7*ep1[0] + 3*ep2[2] + 5*ep2[1] + ep2[0]);
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if(dot < halfPoint)
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step = (dot < c0Point) ? 1 : 3;
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else
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step = (dot < c3Point) ? 2 : 0;
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ep1[1] = dp[1] - stops[step];
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lmask |= step<<2;
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dot = (dp[2] << 4) + (7*ep1[1] + 3*ep2[3] + 5*ep2[2] + ep2[1]);
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if(dot < halfPoint)
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step = (dot < c0Point) ? 1 : 3;
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else
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step = (dot < c3Point) ? 2 : 0;
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ep1[2] = dp[2] - stops[step];
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lmask |= step<<4;
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dot = (dp[3] << 4) + (7*ep1[2] + 5*ep2[3] + ep2[2]);
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if(dot < halfPoint)
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step = (dot < c0Point) ? 1 : 3;
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else
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step = (dot < c3Point) ? 2 : 0;
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ep1[3] = dp[3] - stops[step];
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lmask |= step<<6;
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dp += 4;
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mask |= lmask << (y*8);
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{ int *et = ep1; ep1 = ep2; ep2 = et; } // swap
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}
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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 = 0x7fffffff,maxd = -0x7fffffff;
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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);
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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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// Pick colors at extreme points
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for(i=0;i<16;i++)
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{
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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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}
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static int stb__sclamp(float y, int p0, int p1)
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{
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int x = (int) y;
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if (x < p0) return p0;
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if (x > p1) return p1;
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return x;
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}
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// The refinement function. (Clever code, part 2)
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// Tries to optimize colors to suit block contents better.
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// (By solving a least squares system via normal equations+Cramer's rule)
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static int stb__RefineBlock(unsigned char *block, unsigned short *pmax16, unsigned short *pmin16, unsigned int mask)
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{
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static const int w1Tab[4] = { 3,0,2,1 };
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static const int prods[4] = { 0x090000,0x000900,0x040102,0x010402 };
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// ^some magic to save a lot of multiplies in the accumulating loop...
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// (precomputed products of weights for least squares system, accumulated inside one 32-bit register)
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float frb,fg;
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unsigned short oldMin, oldMax, min16, max16;
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int i, akku = 0, xx,xy,yy;
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int At1_r,At1_g,At1_b;
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int At2_r,At2_g,At2_b;
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unsigned int cm = mask;
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oldMin = *pmin16;
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oldMax = *pmax16;
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if((mask ^ (mask<<2)) < 4) // all pixels have the same index?
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{
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// yes, linear system would be singular; solve using optimal
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// single-color match on average color
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int r = 8, g = 8, b = 8;
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for (i=0;i<16;++i) {
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r += block[i*4+0];
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g += block[i*4+1];
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|
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;
|
|
|
|
frb = 3.0f * 31.0f / 255.0f / (xx*yy - xy*xy);
|
|
fg = frb * 63.0f / 31.0f;
|
|
|
|
// solve.
|
|
max16 = stb__sclamp((At1_r*yy - At2_r*xy)*frb+0.5f,0,31) << 11;
|
|
max16 |= stb__sclamp((At1_g*yy - At2_g*xy)*fg +0.5f,0,63) << 5;
|
|
max16 |= stb__sclamp((At1_b*yy - At2_b*xy)*frb+0.5f,0,31) << 0;
|
|
|
|
min16 = stb__sclamp((At2_r*xx - At1_r*xy)*frb+0.5f,0,31) << 11;
|
|
min16 |= stb__sclamp((At2_g*xx - At1_g*xy)*fg +0.5f,0,63) << 5;
|
|
min16 |= stb__sclamp((At2_b*xx - At1_b*xy)*frb+0.5f,0,31) << 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 dither;
|
|
int refinecount;
|
|
unsigned short max16, min16;
|
|
unsigned char dblock[16*4],color[4*4];
|
|
|
|
dither = mode & STB_DXT_DITHER;
|
|
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: compute dithered version for PCA if desired
|
|
if(dither)
|
|
stb__DitherBlock(dblock,block);
|
|
|
|
// second step: pca+map along principal axis
|
|
stb__OptimizeColorsBlock(dither ? dblock : block,&max16,&min16);
|
|
if (max16 != min16) {
|
|
stb__EvalColors(color,max16,min16);
|
|
mask = stb__MatchColorsBlock(block,color,dither);
|
|
} else
|
|
mask = 0;
|
|
|
|
// third step: refine (multiple times if requested)
|
|
for (i=0;i<refinecount;i++) {
|
|
unsigned int lastmask = mask;
|
|
|
|
if (stb__RefineBlock(dither ? dblock : block,&max16,&min16,mask)) {
|
|
if (max16 != min16) {
|
|
stb__EvalColors(color,max16,min16);
|
|
mask = stb__MatchColorsBlock(block,color,dither);
|
|
} 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
|
|
((unsigned char *)dest)[0] = mx;
|
|
((unsigned char *)dest)[1] = 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++ = mask;
|
|
mask >>= 8;
|
|
bits -= 8;
|
|
}
|
|
}
|
|
}
|
|
|
|
static void stb__InitDXT()
|
|
{
|
|
int i;
|
|
for(i=0;i<32;i++)
|
|
stb__Expand5[i] = (i<<3)|(i>>2);
|
|
|
|
for(i=0;i<64;i++)
|
|
stb__Expand6[i] = (i<<2)|(i>>4);
|
|
|
|
for(i=0;i<256+16;i++)
|
|
{
|
|
int v = i-8 < 0 ? 0 : i-8 > 255 ? 255 : i-8;
|
|
stb__QuantRBTab[i] = stb__Expand5[stb__Mul8Bit(v,31)];
|
|
stb__QuantGTab[i] = stb__Expand6[stb__Mul8Bit(v,63)];
|
|
}
|
|
|
|
stb__PrepareOptTable(&stb__OMatch5[0][0],stb__Expand5,32);
|
|
stb__PrepareOptTable(&stb__OMatch6[0][0],stb__Expand6,64);
|
|
}
|
|
|
|
void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src, int alpha, int mode)
|
|
{
|
|
unsigned char data[16][4];
|
|
static int init=1;
|
|
if (init) {
|
|
stb__InitDXT();
|
|
init=0;
|
|
}
|
|
|
|
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
|
|
|
|
/*
|
|
------------------------------------------------------------------------------
|
|
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.
|
|
------------------------------------------------------------------------------
|
|
*/
|