--- /dev/null
+// 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
+//
+// LICENSE
+//
+// This software is dual-licensed to the public domain and under the following
+// license: you are granted a perpetual, irrevocable license to copy, modify,
+// publish, and distribute this file as you see fit.
+
+#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 <stdlib.h>
+#include <math.h>
+#include <string.h> // 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<size;mn++) {
+ for (mx=0;mx<size;mx++) {
+ int mine = expand[mn];
+ int maxe = expand[mx];
+ int err = abs(stb__Lerp13(maxe, mine) - i);
+
+ // 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 / 100;
+
+ if(err < bestErr)
+ {
+ Table[i*2+0] = mx;
+ Table[i*2+1] = mn;
+ bestErr = err;
+ }
+ }
+ }
+ }
+}
+
+static void stb__EvalColors(unsigned char *color,unsigned short c0,unsigned short c1)
+{
+ stb__From16Bit(color+ 0, c0);
+ stb__From16Bit(color+ 4, c1);
+ stb__Lerp13RGB(color+ 8, color+0, color+4);
+ stb__Lerp13RGB(color+12, color+4, color+0);
+}
+
+// Block dithering function. Simply dithers a block to 565 RGB.
+// (Floyd-Steinberg)
+static void stb__DitherBlock(unsigned char *dest, unsigned char *block)
+{
+ int err[8],*ep1 = err,*ep2 = err+4, *et;
+ int ch,y;
+
+ // process channels seperately
+ for (ch=0; ch<3; ++ch) {
+ unsigned char *bp = block+ch, *dp = dest+ch;
+ unsigned char *quant = (ch == 1) ? stb__QuantGTab+8 : stb__QuantRBTab+8;
+ memset(err, 0, sizeof(err));
+ for(y=0; y<4; ++y) {
+ dp[ 0] = quant[bp[ 0] + ((3*ep2[1] + 5*ep2[0]) >> 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<nIterPower;iter++)
+ {
+ float r = vfr*covf[0] + vfg*covf[1] + vfb*covf[2];
+ float g = vfr*covf[1] + vfg*covf[3] + vfb*covf[4];
+ float b = vfr*covf[2] + vfg*covf[4] + vfb*covf[5];
+
+ vfr = r;
+ vfg = g;
+ vfb = b;
+ }
+
+ magn = fabs(vfr);
+ if (fabs(vfg) > 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<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 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
projects / henge / apc.git / blobdiff