From dcdcf6b73398c794f4c3e74a8ab990c0d9ce3af0 Mon Sep 17 00:00:00 2001 From: nillerusr Date: Thu, 6 Apr 2023 14:36:14 +0300 Subject: [PATCH] togles: don't use alpha channel in dxt1 decompression for textures without it --- togles/linuxwin/cglmtex.cpp | 24 +- togles/linuxwin/decompress.c | 142 +++++--- togles/linuxwin/stb_dxt_104.h | 624 ---------------------------------- 3 files changed, 111 insertions(+), 679 deletions(-) delete mode 100644 togles/linuxwin/stb_dxt_104.h diff --git a/togles/linuxwin/cglmtex.cpp b/togles/linuxwin/cglmtex.cpp index 5ed83df2..f2d62d83 100644 --- a/togles/linuxwin/cglmtex.cpp +++ b/togles/linuxwin/cglmtex.cpp @@ -3409,8 +3409,8 @@ GLvoid *uncompressDXTc(GLsizei width, GLsizei height, GLenum format, GLsizei ima // uncompress a DXTc image // get pixel size of uncompressed image => fixed RGBA int pixelsize = 4; -/* if (format==COMPRESSED_RGB_S3TC_DXT1_EXT) - pixelsize = 3;*/ + if (format == GL_COMPRESSED_RGB_S3TC_DXT1_EXT || format == GL_COMPRESSED_SRGB_S3TC_DXT1_EXT) + pixelsize = 3; // check with the size of the input data stream if the stream is in fact uncompressed if (imageSize == width*height*pixelsize || data==NULL) { // uncompressed stream @@ -3469,16 +3469,16 @@ void CompressedTexImage2D(GLenum target, GLint level, GLenum internalformat, if ((width<=0) || (height<=0)) { return; } - - GLenum format = GL_RGBA; - GLenum intformat = GL_RGBA; - GLenum type = GL_UNSIGNED_BYTE; - GLvoid *pixels = NULL; - - if (isDXTc(internalformat)) { - pixels = NULL; - type = GL_UNSIGNED_BYTE; + bool hasAlpha = (internalformat != GL_COMPRESSED_RGB_S3TC_DXT1_EXT) && (internalformat != GL_COMPRESSED_SRGB_S3TC_DXT1_EXT); + + GLenum format = hasAlpha ? GL_RGBA : GL_RGB; + GLenum intformat = hasAlpha ? GL_RGBA8 : GL_RGB8; + GLenum type = GL_UNSIGNED_BYTE; + GLvoid *pixels = NULL; + + if (isDXTc(internalformat)) + { int srgb = isDXTcSRGB(internalformat); int simpleAlpha = 0; int complexAlpha = 0; @@ -3492,7 +3492,7 @@ void CompressedTexImage2D(GLenum target, GLint level, GLenum internalformat, } if( srgb ) - intformat = GL_SRGB8_ALPHA8; + intformat = hasAlpha ? GL_SRGB8_ALPHA8 : GL_SRGB8; } gGL->glTexImage2D(target, level, intformat, width, height, border, format, type, pixels); diff --git a/togles/linuxwin/decompress.c b/togles/linuxwin/decompress.c index eabd6893..82b6b4a8 100644 --- a/togles/linuxwin/decompress.c +++ b/togles/linuxwin/decompress.c @@ -92,18 +92,17 @@ static void DecompressBlockDXT1Internal (const uint8_t* block, code = *(const uint32_t*)(block + 4); - if (color0 > color1) { - for (j = 0; j < 4; ++j) { - for (i = 0; i < 4; ++i) { - uint32_t finalColor, positionCode; - uint8_t alpha; + for (j = 0; j < 4; ++j) { + for (i = 0; i < 4; ++i) { + uint32_t finalColor, positionCode; + uint8_t alpha; - alpha = alphaValues [j*4+i]; + finalColor = 0; positionCode = (code >> 2*(4*j+i)) & 0x03; + alpha = alphaValues [j*4+i]; - finalColor = 0; - positionCode = (code >> 2*(4*j+i)) & 0x03; - - switch (positionCode) { + if (color0 > color1) { + switch (positionCode) + { case 0: finalColor = PackRGBA(r0, g0, b0, alpha); break; @@ -117,24 +116,7 @@ static void DecompressBlockDXT1Internal (const uint8_t* block, finalColor = PackRGBA((r0+2*r1)/3, (g0+2*g1)/3, (b0+2*b1)/3, alpha); break; } - if(!alpha) - *simpleAlpha = 1; - else if(alpha<0xff) - *complexAlpha = 1; - output [j*outputStride + i] = finalColor; - } - } - } else { - for (j = 0; j < 4; ++j) { - for (i = 0; i < 4; ++i) { - uint32_t finalColor, positionCode; - uint8_t alpha; - - alpha = alphaValues [j*4+i]; - - finalColor = 0; - positionCode = (code >> 2*(4*j+i)) & 0x03; - + } else { switch (positionCode) { case 0: finalColor = PackRGBA(r0, g0, b0, alpha); @@ -150,18 +132,95 @@ static void DecompressBlockDXT1Internal (const uint8_t* block, finalColor = PackRGBA(0, 0, 0, alpha); break; } + } + + if(!alpha) + *simpleAlpha = 1; + else if(alpha<0xff) + *complexAlpha = 1; - if(!alpha) - *simpleAlpha = 1; - else if(alpha<0xff) - *complexAlpha = 1; + output [j*outputStride + i] = finalColor; + } + } +} + +static void DecompressBlockDXT1InternalRGB(const uint8_t* block, uint8_t* output, uint32_t outputStride) +{ + uint32_t temp, code; + + uint16_t color0, color1; + uint8_t r0, g0, b0, r1, g1, b1; + + int i, j; + + color0 = *(const uint16_t*)(block); + color1 = *(const uint16_t*)(block + 2); + + temp = (color0 >> 11) * 255 + 16; + r0 = (uint8_t)((temp/32 + temp)/32); + temp = ((color0 & 0x07E0) >> 5) * 255 + 32; + g0 = (uint8_t)((temp/64 + temp)/64); + temp = (color0 & 0x001F) * 255 + 16; + b0 = (uint8_t)((temp/32 + temp)/32); + + temp = (color1 >> 11) * 255 + 16; + r1 = (uint8_t)((temp/32 + temp)/32); + temp = ((color1 & 0x07E0) >> 5) * 255 + 32; + g1 = (uint8_t)((temp/64 + temp)/64); + temp = (color1 & 0x001F) * 255 + 16; + b1 = (uint8_t)((temp/32 + temp)/32); + + code = *(const uint32_t*)(block + 4); + + for (j = 0; j < 4; ++j) { + for (i = 0; i < 4; ++i) { + uint8_t positionCode, finalR, finalG, finalB; + + positionCode = (code >> 2*(4*j+i)) & 0x03; + + if (color0 > color1) { + + switch (positionCode) { + case 0: + finalR = r0; finalG = g0; finalB = b0; + break; + case 1: + finalR = r1; finalG = g1; finalB = b1; + break; + case 2: + + finalR = (2*r0+r1)/3; finalG = (2*g0+g1)/3; finalB = (2*b0+b1)/3; + break; + case 3: + finalR = (r0+2*r1)/3; finalG = (g0+2*g1)/3; finalB = (b0+2*b1)/3; + break; + } + } else { + switch (positionCode) { + case 0: + finalR = r0; finalG = g0; finalB = b0; + break; + case 1: + finalR = r1; finalG = g1; finalB = b1; + break; + case 2: + finalR = (r0+r1)/2; finalG = (g0+g1)/2; finalB = (b0+b1)/2; + break; + case 3: + finalR = finalG = finalB = 0; + break; + } - output [j*outputStride + i] = finalColor; } + + output[j*outputStride*3 + i*3] = finalR; + output[j*outputStride*3 + i*3+1] = finalG; + output[j*outputStride*3 + i*3+2] = finalB; } } } + /* void DecompressBlockDXT1(): Decompresses one block of a DXT1 texture and stores the resulting pixels at the appropriate offset in 'image'. @@ -176,6 +235,7 @@ void DecompressBlockDXT1(uint32_t x, uint32_t y, uint32_t width, int transparent0, int* simpleAlpha, int *complexAlpha, uint32_t* image) { + static const uint8_t const_alpha [] = { 255, 255, 255, 255, 255, 255, 255, 255, @@ -183,8 +243,12 @@ void DecompressBlockDXT1(uint32_t x, uint32_t y, uint32_t width, 255, 255, 255, 255 }; - DecompressBlockDXT1Internal (blockStorage, - image + x + (y * width), width, transparent0, simpleAlpha, complexAlpha, const_alpha); + + if( transparent0 ) + DecompressBlockDXT1Internal (blockStorage, + image + x + (y * width), width, transparent0, simpleAlpha, complexAlpha, const_alpha); + else + DecompressBlockDXT1InternalRGB(blockStorage, ((uint8_t*)image) + x*3 + (y*3 * width), width); } /* @@ -331,11 +395,3 @@ void DecompressBlockDXT3(uint32_t x, uint32_t y, uint32_t width, DecompressBlockDXT1Internal (blockStorage, image + x + (y * width), width, transparent0, simpleAlpha, complexAlpha, alphaValues); } - -// Texture DXT1 / DXT5 compression -// Using STB "on file" library -// go there https://github.com/nothings/stb -// for more details and other libs - -#define STB_DXT_IMPLEMENTATION -#include "stb_dxt_104.h" diff --git a/togles/linuxwin/stb_dxt_104.h b/togles/linuxwin/stb_dxt_104.h deleted file mode 100644 index bec72798..00000000 --- a/togles/linuxwin/stb_dxt_104.h +++ /dev/null @@ -1,624 +0,0 @@ -// stb_dxt.h - v1.04 - DXT1/DXT5 compressor - public domain -// original by fabian "ryg" giesen - ported to C by stb -// use '#define STB_DXT_IMPLEMENTATION' before including to create the implementation -// -// USAGE: -// call stb_compress_dxt_block() for every block (you must pad) -// source should be a 4x4 block of RGBA data in row-major order; -// A is ignored if you specify alpha=0; you can turn on dithering -// and "high quality" using mode. -// -// version history: -// v1.04 - (ryg) default to no rounding bias for lerped colors (as per S3TC/DX10 spec); -// single color match fix (allow for inexact color interpolation); -// optimal DXT5 index finder; "high quality" mode that runs multiple refinement steps. -// v1.03 - (stb) endianness support -// v1.02 - (stb) fix alpha encoding bug -// v1.01 - (stb) fix bug converting to RGB that messed up quality, thanks ryg & cbloom -// v1.00 - (stb) first release - -#ifndef STB_INCLUDE_STB_DXT_H -#define STB_INCLUDE_STB_DXT_H - -// compression mode (bitflags) -#define STB_DXT_NORMAL 0 -#define STB_DXT_DITHER 1 // use dithering. dubious win. never use for normal maps and the like! -#define STB_DXT_HIGHQUAL 2 // high quality mode, does two refinement steps instead of 1. ~30-40% slower. - -void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src, int alpha, int mode); -#define STB_COMPRESS_DXT_BLOCK - -#ifdef STB_DXT_IMPLEMENTATION - -// configuration options for DXT encoder. set them in the project/makefile or just define -// them at the top. - -// STB_DXT_USE_ROUNDING_BIAS -// use a rounding bias during color interpolation. this is closer to what "ideal" -// interpolation would do but doesn't match the S3TC/DX10 spec. old versions (pre-1.03) -// implicitly had this turned on. -// -// in case you're targeting a specific type of hardware (e.g. console programmers): -// NVidia and Intel GPUs (as of 2010) as well as DX9 ref use DXT decoders that are closer -// to STB_DXT_USE_ROUNDING_BIAS. AMD/ATI, S3 and DX10 ref are closer to rounding with no bias. -// you also see "(a*5 + b*3) / 8" on some old GPU designs. -// #define STB_DXT_USE_ROUNDING_BIAS - -#include -#include -#include // memset - -static unsigned char stb__Expand5[32]; -static unsigned char stb__Expand6[64]; -static unsigned char stb__OMatch5[256][2]; -static unsigned char stb__OMatch6[256][2]; -static unsigned char stb__QuantRBTab[256+16]; -static unsigned char stb__QuantGTab[256+16]; - -static int stb__Mul8Bit(int a, int b) -{ - int t = a*b + 128; - return (t + (t >> 8)) >> 8; -} - -static void stb__From16Bit(unsigned char *out, unsigned short v) -{ - int rv = (v & 0xf800) >> 11; - int gv = (v & 0x07e0) >> 5; - int bv = (v & 0x001f) >> 0; - - out[0] = stb__Expand5[rv]; - out[1] = stb__Expand6[gv]; - out[2] = stb__Expand5[bv]; - out[3] = 0; -} - -static unsigned short stb__As16Bit(int r, int g, int b) -{ - return (stb__Mul8Bit(r,31) << 11) + (stb__Mul8Bit(g,63) << 5) + stb__Mul8Bit(b,31); -} - -// linear interpolation at 1/3 point between a and b, using desired rounding type -static int stb__Lerp13(int a, int b) -{ -#ifdef STB_DXT_USE_ROUNDING_BIAS - // with rounding bias - return a + stb__Mul8Bit(b-a, 0x55); -#else - // without rounding bias - // replace "/ 3" by "* 0xaaab) >> 17" if your compiler sucks or you really need every ounce of speed. - return (2*a + b) / 3; -#endif -} - -// lerp RGB color -static void stb__Lerp13RGB(unsigned char *out, unsigned char *p1, unsigned char *p2) -{ - out[0] = stb__Lerp13(p1[0], p2[0]); - out[1] = stb__Lerp13(p1[1], p2[1]); - out[2] = stb__Lerp13(p1[2], p2[2]); -} - -/****************************************************************************/ - -// compute table to reproduce constant colors as accurately as possible -static void stb__PrepareOptTable(unsigned char *Table,const unsigned char *expand,int size) -{ - int i,mn,mx; - for (i=0;i<256;i++) { - int bestErr = 256; - for (mn=0;mn> 4)]; - ep1[0] = bp[ 0] - dp[ 0]; - dp[ 4] = quant[bp[ 4] + ((7*ep1[0] + 3*ep2[2] + 5*ep2[1] + ep2[0]) >> 4)]; - ep1[1] = bp[ 4] - dp[ 4]; - dp[ 8] = quant[bp[ 8] + ((7*ep1[1] + 3*ep2[3] + 5*ep2[2] + ep2[1]) >> 4)]; - ep1[2] = bp[ 8] - dp[ 8]; - dp[12] = quant[bp[12] + ((7*ep1[2] + 5*ep2[3] + ep2[2]) >> 4)]; - ep1[3] = bp[12] - dp[12]; - bp += 16; - dp += 16; - et = ep1, ep1 = ep2, ep2 = et; // swap - } - } -} - -// The color matching function -static unsigned int stb__MatchColorsBlock(unsigned char *block, unsigned char *color,int dither) -{ - unsigned int mask = 0; - int dirr = color[0*4+0] - color[1*4+0]; - int dirg = color[0*4+1] - color[1*4+1]; - int dirb = color[0*4+2] - color[1*4+2]; - int dots[16]; - int stops[4]; - int i; - int c0Point, halfPoint, c3Point; - - for(i=0;i<16;i++) - dots[i] = block[i*4+0]*dirr + block[i*4+1]*dirg + block[i*4+2]*dirb; - - for(i=0;i<4;i++) - stops[i] = color[i*4+0]*dirr + color[i*4+1]*dirg + color[i*4+2]*dirb; - - // think of the colors as arranged on a line; project point onto that line, then choose - // next color out of available ones. we compute the crossover points for "best color in top - // half"/"best in bottom half" and then the same inside that subinterval. - // - // relying on this 1d approximation isn't always optimal in terms of euclidean distance, - // but it's very close and a lot faster. - // http://cbloomrants.blogspot.com/2008/12/12-08-08-dxtc-summary.html - - c0Point = (stops[1] + stops[3]) >> 1; - halfPoint = (stops[3] + stops[2]) >> 1; - c3Point = (stops[2] + stops[0]) >> 1; - - if(!dither) { - // the version without dithering is straightforward - for (i=15;i>=0;i--) { - int dot = dots[i]; - mask <<= 2; - - if(dot < halfPoint) - mask |= (dot < c0Point) ? 1 : 3; - else - mask |= (dot < c3Point) ? 2 : 0; - } - } else { - // with floyd-steinberg dithering - int err[8],*ep1 = err,*ep2 = err+4; - int *dp = dots, y; - - c0Point <<= 4; - halfPoint <<= 4; - c3Point <<= 4; - for(i=0;i<8;i++) - err[i] = 0; - - for(y=0;y<4;y++) - { - int dot,lmask,step; - - dot = (dp[0] << 4) + (3*ep2[1] + 5*ep2[0]); - if(dot < halfPoint) - step = (dot < c0Point) ? 1 : 3; - else - step = (dot < c3Point) ? 2 : 0; - ep1[0] = dp[0] - stops[step]; - lmask = step; - - dot = (dp[1] << 4) + (7*ep1[0] + 3*ep2[2] + 5*ep2[1] + ep2[0]); - if(dot < halfPoint) - step = (dot < c0Point) ? 1 : 3; - else - step = (dot < c3Point) ? 2 : 0; - ep1[1] = dp[1] - stops[step]; - lmask |= step<<2; - - dot = (dp[2] << 4) + (7*ep1[1] + 3*ep2[3] + 5*ep2[2] + ep2[1]); - if(dot < halfPoint) - step = (dot < c0Point) ? 1 : 3; - else - step = (dot < c3Point) ? 2 : 0; - ep1[2] = dp[2] - stops[step]; - lmask |= step<<4; - - dot = (dp[3] << 4) + (7*ep1[2] + 5*ep2[3] + ep2[2]); - if(dot < halfPoint) - step = (dot < c0Point) ? 1 : 3; - else - step = (dot < c3Point) ? 2 : 0; - ep1[3] = dp[3] - stops[step]; - lmask |= step<<6; - - dp += 4; - mask |= lmask << (y*8); - { int *et = ep1; ep1 = ep2; ep2 = et; } // swap - } - } - - return mask; -} - -// The color optimization function. (Clever code, part 1) -static void stb__OptimizeColorsBlock(unsigned char *block, unsigned short *pmax16, unsigned short *pmin16) -{ - int mind = 0x7fffffff,maxd = -0x7fffffff; - unsigned char *minp, *maxp; - double magn; - int v_r,v_g,v_b; - static const int nIterPower = 4; - float covf[6],vfr,vfg,vfb; - - // determine color distribution - int cov[6]; - int mu[3],min[3],max[3]; - int ch,i,iter; - - for(ch=0;ch<3;ch++) - { - const unsigned char *bp = ((const unsigned char *) block) + ch; - int muv,minv,maxv; - - muv = minv = maxv = bp[0]; - for(i=4;i<64;i+=4) - { - muv += bp[i]; - if (bp[i] < minv) minv = bp[i]; - else if (bp[i] > maxv) maxv = bp[i]; - } - - mu[ch] = (muv + 8) >> 4; - min[ch] = minv; - max[ch] = maxv; - } - - // determine covariance matrix - for (i=0;i<6;i++) - cov[i] = 0; - - for (i=0;i<16;i++) - { - int r = block[i*4+0] - mu[0]; - int g = block[i*4+1] - mu[1]; - int b = block[i*4+2] - mu[2]; - - cov[0] += r*r; - cov[1] += r*g; - cov[2] += r*b; - cov[3] += g*g; - cov[4] += g*b; - cov[5] += b*b; - } - - // convert covariance matrix to float, find principal axis via power iter - for(i=0;i<6;i++) - covf[i] = 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 magn) magn = fabs(vfg); - if (fabs(vfb) > magn) magn = 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); - } - - // Pick colors at extreme points - for(i=0;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 int stb__sclamp(float y, int p0, int p1) -{ - int x = (int) y; - if (x < p0) return p0; - if (x > p1) return p1; - return x; -} - -// 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 frb,fg; - 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; - - 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> 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 mode) -{ - int i,dist,bias,dist4,dist2,bits,mask; - - // find min/max color - int mn,mx; - mn = mx = src[3]; - - for (i=1;i<16;i++) - { - if (src[i*4+3] < mn) mn = src[i*4+3]; - else if (src[i*4+3] > mx) mx = src[i*4+3]; - } - - // 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*4+3]*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) -{ - static int init=1; - if (init) { - stb__InitDXT(); - init=0; - } - - if (alpha) { - stb__CompressAlphaBlock(dest,(unsigned char*) src,mode); - dest += 8; - } - - stb__CompressColorBlock(dest,(unsigned char*) src,mode); -} -#endif // STB_DXT_IMPLEMENTATION - -#endif // STB_INCLUDE_STB_DXT_H