--- /dev/null
+// stb_dxt.h - v1.10 - 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;
+// Alpha channel is not stored if you specify alpha=0 (but you
+// must supply some constant alpha in the alpha channel).
+// You can turn on dithering and "high quality" using mode.
+//
+// version history:
+// v1.10 - (i.c) various small quality improvements
+// v1.09 - (stb) update documentation re: surprising alpha channel requirement
+// v1.08 - (stb) fix bug in dxt-with-alpha block
+// v1.07 - (stb) bc4; allow not using libc; add STB_DXT_STATIC
+// v1.06 - (stb) fix to known-broken 1.05
+// v1.05 - (stb) support bc5/3dc (Arvids Kokins), use extern "C" in C++ (Pavel Krajcevski)
+// 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
+//
+// contributors:
+// Rich Geldreich (more accurate index selection)
+// Kevin Schmidt (#defines for "freestanding" compilation)
+// github:ppiastucki (BC4 support)
+// Ignacio Castano - improve DXT endpoint quantization
+//
+// LICENSE
+//
+// See end of file for license information.
+
+#ifndef STB_INCLUDE_STB_DXT_H
+#define STB_INCLUDE_STB_DXT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef STB_DXT_STATIC
+#define STBDDEF static
+#else
+#define STBDDEF extern
+#endif
+
+// 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.
+
+STBDDEF void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src_rgba_four_bytes_per_pixel, int alpha, int mode);
+STBDDEF void stb_compress_bc4_block(unsigned char *dest, const unsigned char *src_r_one_byte_per_pixel);
+STBDDEF void stb_compress_bc5_block(unsigned char *dest, const unsigned char *src_rg_two_byte_per_pixel);
+
+#define STB_COMPRESS_DXT_BLOCK
+
+#ifdef __cplusplus
+}
+#endif
+#endif // STB_INCLUDE_STB_DXT_H
+
+#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>
+
+#if !defined(STBD_ABS) || !defined(STBI_FABS)
+#include <math.h>
+#endif
+
+#ifndef STBD_ABS
+#define STBD_ABS(i) abs(i)
+#endif
+
+#ifndef STBD_FABS
+#define STBD_FABS(x) fabs(x)
+#endif
+
+#ifndef STBD_MEMSET
+#include <string.h>
+#define STBD_MEMSET memset
+#endif
+
+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 (unsigned short)((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] = (unsigned char)stb__Lerp13(p1[0], p2[0]);
+ out[1] = (unsigned char)stb__Lerp13(p1[1], p2[1]);
+ out[2] = (unsigned char)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 = STBD_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 += STBD_ABS(maxe - mine) * 3 / 100;
+
+ if(err < bestErr)
+ {
+ Table[i*2+0] = (unsigned char)mx;
+ Table[i*2+1] = (unsigned char)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 separately
+ 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;
+ STBD_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]);
+ halfPoint = (stops[3] + stops[2]);
+ c3Point = (stops[2] + stops[0]);
+
+ if(!dither) {
+ // the version without dithering is straightforward
+ for (i=15;i>=0;i--) {
+ int dot = dots[i]*2;
+ 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 <<= 3;
+ halfPoint <<= 3;
+ c3Point <<= 3;
+ 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 = STBD_FABS(vfr);
+ if (STBD_FABS(vfg) > magn) magn = STBD_FABS(vfg);
+ if (STBD_FABS(vfb) > magn) magn = STBD_FABS(vfb);
+
+ if(magn < 4.0f) { // too small, default to luminance
+ v_r = 299; // JPEG YCbCr luma coefs, scaled by 1000.
+ v_g = 587;
+ v_b = 114;
+ } else {
+ magn = 512.0 / magn;
+ v_r = (int) (vfr * magn);
+ v_g = (int) (vfg * magn);
+ v_b = (int) (vfb * magn);
+ }
+
+ // 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 const float 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 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 > 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 > 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 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
+ 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;
+ }
+ }
+}
+
+static void stb__InitDXT()
+{
+ int i;
+ for(i=0;i<32;i++)
+ stb__Expand5[i] = (unsigned char)((i<<3)|(i>>2));
+
+ for(i=0;i<64;i++)
+ stb__Expand6[i] = (unsigned char)((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.
+------------------------------------------------------------------------------
+*/
projects / convexer.git / blobdiff