610 lines
15 KiB
C++
610 lines
15 KiB
C++
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// File: crn_ryg_dxt.cpp
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// RYG's real-time DXT compressor - Public domain.
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#include "crn_core.h"
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#include "crn_ryg_types.hpp"
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#include "crn_ryg_dxt.hpp"
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#ifdef _MSC_VER
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#pragma warning (disable: 4244) // conversion from 'a' to 'b', possible loss of data
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#endif
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namespace ryg_dxt
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{
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// Couple of tables...
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sU8 Expand5[32];
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sU8 Expand6[64];
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sU8 OMatch5[256][2];
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sU8 OMatch6[256][2];
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sU8 OMatch5_3[256][2];
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sU8 OMatch6_3[256][2];
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sU8 QuantRBTab[256+16];
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sU8 QuantGTab[256+16];
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static sInt Mul8Bit(sInt a,sInt b)
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{
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sInt t = a*b + 128;
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return (t + (t >> 8)) >> 8;
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}
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union Pixel
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{
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struct
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{
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sU8 b,g,r,a;
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};
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sU32 v;
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void From16Bit(sU16 v)
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{
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sInt rv = (v & 0xf800) >> 11;
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sInt gv = (v & 0x07e0) >> 5;
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sInt bv = (v & 0x001f) >> 0;
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a = 0;
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r = Expand5[rv];
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g = Expand6[gv];
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b = Expand5[bv];
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}
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sU16 As16Bit() const
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{
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return (Mul8Bit(r,31) << 11) + (Mul8Bit(g,63) << 5) + Mul8Bit(b,31);
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}
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void LerpRGB(const Pixel &p1,const Pixel &p2,sInt f)
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{
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r = p1.r + Mul8Bit(p2.r - p1.r,f);
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g = p1.g + Mul8Bit(p2.g - p1.g,f);
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b = p1.b + Mul8Bit(p2.b - p1.b,f);
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}
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};
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/****************************************************************************/
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static void PrepareOptTable4(sU8 *Table,const sU8 *expand,sInt size)
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{
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for(sInt i=0;i<256;i++)
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{
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sInt bestErr = 256;
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for(sInt min=0;min<size;min++)
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{
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for(sInt max=0;max<size;max++)
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{
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sInt mine = expand[min];
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sInt maxe = expand[max];
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//sInt err = sAbs(maxe + Mul8Bit(mine-maxe,0x55) - i);
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sInt err = sAbs(((maxe*2+mine)/3) - i);
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err += ((sAbs(maxe-mine)*8)>>8); // approx. .03f
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if(err < bestErr)
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{
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Table[i*2+0] = max;
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Table[i*2+1] = min;
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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 PrepareOptTable3(sU8 *Table,const sU8 *expand,sInt size)
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{
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for(sInt i=0;i<256;i++)
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{
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sInt bestErr = 256;
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for(sInt min=0;min<size;min++)
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{
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for(sInt max=0;max<size;max++)
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{
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sInt mine = expand[min];
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sInt maxe = expand[max];
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sInt err = sAbs(((mine + maxe) >> 1) - i);
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err += ((sAbs(maxe-mine)*8)>>8); // approx. .03f
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if(err < bestErr)
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{
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Table[i*2+0] = max;
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Table[i*2+1] = min;
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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 inline void EvalColors(Pixel *color,sU16 c0,sU16 c1)
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{
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color[0].From16Bit(c0);
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color[1].From16Bit(c1);
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color[2].LerpRGB(color[0],color[1],0x55);
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color[3].LerpRGB(color[0],color[1],0xaa);
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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 DitherBlock(Pixel *dest,const Pixel *block)
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{
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sInt err[8],*ep1 = err,*ep2 = err+4;
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// process channels seperately
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for(sInt ch=0;ch<3;ch++)
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{
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sU8 *bp = (sU8 *) block;
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sU8 *dp = (sU8 *) dest;
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sU8 *quant = (ch == 1) ? QuantGTab+8 : QuantRBTab+8;
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bp += ch;
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dp += ch;
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sSetMem(err,0,sizeof(err));
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for(sInt y=0;y<4;y++)
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{
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// pixel 0
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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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// pixel 1
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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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// pixel 2
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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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// pixel 3
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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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// advance to next line
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sSwap(ep1,ep2);
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bp += 16;
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dp += 16;
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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 sU32 MatchColorsBlock(const Pixel *block,const Pixel *color,sBool dither)
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{
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sU32 mask = 0;
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sInt dirr = color[0].r - color[1].r;
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sInt dirg = color[0].g - color[1].g;
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sInt dirb = color[0].b - color[1].b;
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sInt dots[16];
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for(sInt i=0;i<16;i++)
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dots[i] = block[i].r*dirr + block[i].g*dirg + block[i].b*dirb;
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sInt stops[4];
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for(sInt i=0;i<4;i++)
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stops[i] = color[i].r*dirr + color[i].g*dirg + color[i].b*dirb;
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sInt c0Point = (stops[1] + stops[3]) >> 1;
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sInt halfPoint = (stops[3] + stops[2]) >> 1;
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sInt c3Point = (stops[2] + stops[0]) >> 1;
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if(!dither)
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{
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// the version without dithering is straightforward
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for(sInt i=15;i>=0;i--)
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{
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mask <<= 2;
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sInt dot = dots[i];
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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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}
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else
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{
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// with floyd-steinberg dithering (see above)
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sInt err[8],*ep1 = err,*ep2 = err+4;
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sInt *dp = dots;
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c0Point <<= 4;
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halfPoint <<= 4;
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c3Point <<= 4;
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for(sInt i=0;i<8;i++)
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err[i] = 0;
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for(sInt y=0;y<4;y++)
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{
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sInt dot,lmask,step;
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// pixel 0
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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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// pixel 1
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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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// pixel 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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// pixel 3
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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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// advance to next line
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sSwap(ep1,ep2);
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dp += 4;
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mask |= lmask << (y*8);
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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 OptimizeColorsBlock(const Pixel *block,sU16 &max16,sU16 &min16)
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{
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static const sInt nIterPower = 4;
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// determine color distribution
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sInt mu[3],min[3],max[3];
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for(sInt ch=0;ch<3;ch++)
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{
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const sU8 *bp = ((const sU8 *) block) + ch;
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sInt muv,minv,maxv;
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muv = minv = maxv = bp[0];
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for(sInt i=4;i<64;i+=4)
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{
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muv += bp[i];
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minv = sMin<sInt>(minv,bp[i]);
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maxv = sMax<sInt>(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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sInt cov[6];
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for(sInt i=0;i<6;i++)
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cov[i] = 0;
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for(sInt i=0;i<16;i++)
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{
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sInt r = block[i].r - mu[2];
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sInt g = block[i].g - mu[1];
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sInt b = block[i].b - mu[0];
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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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sF32 covf[6],vfr,vfg,vfb;
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for(sInt i=0;i<6;i++)
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covf[i] = cov[i] / 255.0f;
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vfr = max[2] - min[2];
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vfg = max[1] - min[1];
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vfb = max[0] - min[0];
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for(sInt iter=0;iter<nIterPower;iter++)
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{
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sF32 r = vfr*covf[0] + vfg*covf[1] + vfb*covf[2];
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sF32 g = vfr*covf[1] + vfg*covf[3] + vfb*covf[4];
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sF32 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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sF32 magn = sMax(sMax(sFAbs(vfr),sFAbs(vfg)),sFAbs(vfb));
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sInt v_r,v_g,v_b;
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if(magn < 4.0f) // too small, default to luminance
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{
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v_r = 148;
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v_g = 300;
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v_b = 58;
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}
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else
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{
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magn = 512.0f / magn;
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v_r = vfr * magn;
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v_g = vfg * magn;
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v_b = vfb * magn;
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}
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// Pick colors at extreme points
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sInt mind = 0x7fffffff,maxd = -0x7fffffff;
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Pixel minp,maxp;
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for(sInt i=0;i<16;i++)
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{
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sInt dot = block[i].r*v_r + block[i].g*v_g + block[i].b*v_b;
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if(dot < mind)
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{
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mind = dot;
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minp = block[i];
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}
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if(dot > maxd)
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{
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maxd = dot;
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maxp = block[i];
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}
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}
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// Reduce to 16 bit colors
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max16 = maxp.As16Bit();
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|
|
min16 = minp.As16Bit();
|
||
|
|
}
|
||
|
|
|
||
|
|
// 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 sBool RefineBlock(const Pixel *block,sU16 &max16,sU16 &min16,sU32 mask)
|
||
|
|
{
|
||
|
|
static const sInt w1Tab[4] = { 3,0,2,1 };
|
||
|
|
static const sInt prods[4] = { 0x090000,0x000900,0x040102,0x010402 };
|
||
|
|
// ^some magic to save a lot of multiplies in the accumulating loop...
|
||
|
|
|
||
|
|
sInt akku = 0;
|
||
|
|
sInt At1_r,At1_g,At1_b;
|
||
|
|
sInt At2_r,At2_g,At2_b;
|
||
|
|
sU32 cm = mask;
|
||
|
|
|
||
|
|
At1_r = At1_g = At1_b = 0;
|
||
|
|
At2_r = At2_g = At2_b = 0;
|
||
|
|
for(sInt i=0;i<16;i++,cm>>=2)
|
||
|
|
{
|
||
|
|
sInt step = cm&3;
|
||
|
|
sInt w1 = w1Tab[step];
|
||
|
|
sInt r = block[i].r;
|
||
|
|
sInt g = block[i].g;
|
||
|
|
sInt b = block[i].b;
|
||
|
|
|
||
|
|
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
|
||
|
|
sInt xx = akku >> 16;
|
||
|
|
sInt yy = (akku >> 8) & 0xff;
|
||
|
|
sInt xy = (akku >> 0) & 0xff;
|
||
|
|
|
||
|
|
if(!yy || !xx || xx*yy == xy*xy)
|
||
|
|
return sFALSE;
|
||
|
|
|
||
|
|
sF32 frb = 3.0f * 31.0f / 255.0f / (xx*yy - xy*xy);
|
||
|
|
sF32 fg = frb * 63.0f / 31.0f;
|
||
|
|
|
||
|
|
sU16 oldMin = min16;
|
||
|
|
sU16 oldMax = max16;
|
||
|
|
|
||
|
|
// solve.
|
||
|
|
max16 = sClamp<sInt>((At1_r*yy - At2_r*xy)*frb+0.5f,0,31) << 11;
|
||
|
|
max16 |= sClamp<sInt>((At1_g*yy - At2_g*xy)*fg +0.5f,0,63) << 5;
|
||
|
|
max16 |= sClamp<sInt>((At1_b*yy - At2_b*xy)*frb+0.5f,0,31) << 0;
|
||
|
|
|
||
|
|
min16 = sClamp<sInt>((At2_r*xx - At1_r*xy)*frb+0.5f,0,31) << 11;
|
||
|
|
min16 |= sClamp<sInt>((At2_g*xx - At1_g*xy)*fg +0.5f,0,63) << 5;
|
||
|
|
min16 |= sClamp<sInt>((At2_b*xx - At1_b*xy)*frb+0.5f,0,31) << 0;
|
||
|
|
|
||
|
|
return oldMin != min16 || oldMax != max16;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Color block compression
|
||
|
|
static void CompressColorBlock(sU8 *dest,const sU32 *src,sInt quality)
|
||
|
|
{
|
||
|
|
const Pixel *block = (const Pixel *) src;
|
||
|
|
Pixel dblock[16],color[4];
|
||
|
|
|
||
|
|
// check if block is constant
|
||
|
|
sU32 min,max;
|
||
|
|
min = max = block[0].v;
|
||
|
|
|
||
|
|
for(sInt i=1;i<16;i++)
|
||
|
|
{
|
||
|
|
min = sMin(min,block[i].v);
|
||
|
|
max = sMax(max,block[i].v);
|
||
|
|
}
|
||
|
|
|
||
|
|
// perform block compression
|
||
|
|
sU16 min16,max16;
|
||
|
|
sU32 mask;
|
||
|
|
|
||
|
|
if(min != max) // no constant color
|
||
|
|
{
|
||
|
|
// first step: compute dithered version for PCA if desired
|
||
|
|
if(quality)
|
||
|
|
DitherBlock(dblock,block);
|
||
|
|
|
||
|
|
// second step: pca+map along principal axis
|
||
|
|
OptimizeColorsBlock(quality ? dblock : block,max16,min16);
|
||
|
|
if(max16 != min16)
|
||
|
|
{
|
||
|
|
EvalColors(color,max16,min16);
|
||
|
|
mask = MatchColorsBlock(block,color,quality != 0);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
mask = 0;
|
||
|
|
|
||
|
|
// third step: refine
|
||
|
|
if(RefineBlock(quality ? dblock : block,max16,min16,mask))
|
||
|
|
{
|
||
|
|
if(max16 != min16)
|
||
|
|
{
|
||
|
|
EvalColors(color,max16,min16);
|
||
|
|
mask = MatchColorsBlock(block,color,quality != 0);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
mask = 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
}
|
||
|
|
else // constant color
|
||
|
|
{
|
||
|
|
sInt r = block[0].r;
|
||
|
|
sInt g = block[0].g;
|
||
|
|
sInt b = block[0].b;
|
||
|
|
|
||
|
|
mask = 0xaaaaaaaa;
|
||
|
|
max16 = (OMatch5[r][0]<<11) | (OMatch6[g][0]<<5) | OMatch5[b][0];
|
||
|
|
min16 = (OMatch5[r][1]<<11) | (OMatch6[g][1]<<5) | OMatch5[b][1];
|
||
|
|
}
|
||
|
|
|
||
|
|
// write the color block
|
||
|
|
if(max16 < min16)
|
||
|
|
{
|
||
|
|
sSwap(max16,min16);
|
||
|
|
mask ^= 0x55555555;
|
||
|
|
}
|
||
|
|
|
||
|
|
((sU16 *) dest)[0] = max16;
|
||
|
|
((sU16 *) dest)[1] = min16;
|
||
|
|
((sU32 *) dest)[1] = mask;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Alpha block compression (this is easy for a change)
|
||
|
|
static void CompressAlphaBlock(sU8 *dest,const sU32 *src,sInt quality)
|
||
|
|
{
|
||
|
|
quality;
|
||
|
|
const Pixel *block = (const Pixel *) src;
|
||
|
|
|
||
|
|
// find min/max color
|
||
|
|
sInt min,max;
|
||
|
|
min = max = block[0].a;
|
||
|
|
|
||
|
|
for(sInt i=1;i<16;i++)
|
||
|
|
{
|
||
|
|
min = sMin<sInt>(min,block[i].a);
|
||
|
|
max = sMax<sInt>(max,block[i].a);
|
||
|
|
}
|
||
|
|
|
||
|
|
// encode them
|
||
|
|
*dest++ = max;
|
||
|
|
*dest++ = min;
|
||
|
|
|
||
|
|
// determine bias and emit color indices
|
||
|
|
sInt dist = max-min;
|
||
|
|
sInt bias = min*7 - (dist >> 1);
|
||
|
|
sInt dist4 = dist*4;
|
||
|
|
sInt dist2 = dist*2;
|
||
|
|
sInt bits = 0,mask=0;
|
||
|
|
|
||
|
|
for(sInt i=0;i<16;i++)
|
||
|
|
{
|
||
|
|
sInt a = block[i].a*7 - bias;
|
||
|
|
sInt ind,t;
|
||
|
|
|
||
|
|
// select index (hooray for bit magic)
|
||
|
|
t = (dist4 - a) >> 31; ind = t & 4; a -= dist4 & t;
|
||
|
|
t = (dist2 - a) >> 31; ind += t & 2; a -= dist2 & t;
|
||
|
|
t = (dist - a) >> 31; ind += t & 1;
|
||
|
|
|
||
|
|
ind = -ind & 7;
|
||
|
|
ind ^= (2 > ind);
|
||
|
|
|
||
|
|
// write index
|
||
|
|
mask |= ind << bits;
|
||
|
|
if((bits += 3) >= 8)
|
||
|
|
{
|
||
|
|
*dest++ = mask;
|
||
|
|
mask >>= 8;
|
||
|
|
bits -= 8;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/****************************************************************************/
|
||
|
|
|
||
|
|
void sInitDXT()
|
||
|
|
{
|
||
|
|
for(sInt i=0;i<32;i++)
|
||
|
|
Expand5[i] = (i<<3)|(i>>2);
|
||
|
|
|
||
|
|
for(sInt i=0;i<64;i++)
|
||
|
|
Expand6[i] = (i<<2)|(i>>4);
|
||
|
|
|
||
|
|
for(sInt i=0;i<256+16;i++)
|
||
|
|
{
|
||
|
|
sInt v = sClamp(i-8,0,255);
|
||
|
|
QuantRBTab[i] = Expand5[Mul8Bit(v,31)];
|
||
|
|
QuantGTab[i] = Expand6[Mul8Bit(v,63)];
|
||
|
|
}
|
||
|
|
|
||
|
|
PrepareOptTable4(&OMatch5[0][0],Expand5,32);
|
||
|
|
PrepareOptTable4(&OMatch6[0][0],Expand6,64);
|
||
|
|
|
||
|
|
PrepareOptTable3(&OMatch5_3[0][0],Expand5,32);
|
||
|
|
PrepareOptTable3(&OMatch6_3[0][0],Expand6,64);
|
||
|
|
}
|
||
|
|
|
||
|
|
void sCompressDXTBlock(sU8 *dest,const sU32 *src,sBool alpha,sInt quality)
|
||
|
|
{
|
||
|
|
CRNLIB_ASSERT(Expand5[1]);
|
||
|
|
|
||
|
|
// if alpha specified, compress alpha as well
|
||
|
|
if(alpha)
|
||
|
|
{
|
||
|
|
CompressAlphaBlock(dest,src,quality);
|
||
|
|
dest += 8;
|
||
|
|
}
|
||
|
|
|
||
|
|
// compress the color part
|
||
|
|
CompressColorBlock(dest,src,quality);
|
||
|
|
}
|
||
|
|
|
||
|
|
void sCompressDXT5ABlock(sU8 *dest,const sU32 *src,sInt quality)
|
||
|
|
{
|
||
|
|
CRNLIB_ASSERT(Expand5[1]);
|
||
|
|
|
||
|
|
CompressAlphaBlock(dest,src,quality);
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace ryg_dxt
|
||
|
|
|