ref: 832eb032a1ed49e8704e0178eab312a7aa47bcee
dir: /src/zdither.c/
/* * Highly optimised dithering 16 bits -> 8 bits. * The formulas were taken in Mesa (Bob Mercier mercier@hollywood.cinenet.net). */ #include <stdlib.h> #include <stdio.h> #include "../include/zbuffer.h" #include <assert.h> #if defined(TGL_FEATURE_8_BITS) #define _R 5 #define _G 9 #define _B 5 #define _DX 4 #define _DY 4 #define _D (_DX*_DY) #define _MIX(r,g,b) ( ((g)<<6) | ((b)<<3) | (r) ) #define DITHER_TABLE_SIZE (1 << 15) #define DITHER_INDEX(r,g,b) ((b) + (g) * _B + (r) * (_B * _G)) #define MAXC 256 static int kernel8[_DY*_DX] = { 0 * MAXC, 8 * MAXC, 2 * MAXC, 10 * MAXC, 12 * MAXC, 4 * MAXC, 14 * MAXC, 6 * MAXC, 3 * MAXC, 11 * MAXC, 1 * MAXC, 9 * MAXC, 15 * MAXC, 7 * MAXC, 13 * MAXC, 5 * MAXC, }; /* we build the color table and the lookup table */ void ZB_initDither(ZBuffer *zb,int nb_colors, unsigned char *color_indexes,int *color_table) { int c,r,g,b,i,index,r1,g1,b1; if (nb_colors < (_R * _G * _B)) { fprintf(stderr,"zdither: not enough colors\n"); exit(1); } for(i=0;i<nb_colors;i++) color_table[i]=0; zb->nb_colors=nb_colors; zb->ctable=gl_malloc(nb_colors * sizeof(int)); for (r = 0; r < _R; r++) { for (g = 0; g < _G; g++) { for (b = 0; b < _B; b++) { r1=(r*255) / (_R - 1); g1=(g*255) / (_G - 1); b1=(b*255) / (_B - 1); index=DITHER_INDEX(r,g,b); c=(r1 << 16) | (g1 << 8) | b1; zb->ctable[index]=c; color_table[index]=c; } } } zb->dctable=gl_malloc( DITHER_TABLE_SIZE ); for(i=0;i<DITHER_TABLE_SIZE;i++) { r=(i >> 12) & 0x7; g=(i >> 8) & 0xF; b=(i >> 3) & 0x7; index=DITHER_INDEX(r,g,b); zb->dctable[i]=color_indexes[index]; } } void ZB_closeDither(ZBuffer *zb) { gl_free(zb->ctable); gl_free(zb->dctable); } #if 0 int ZDither_lookupColor(int r,int g,int b) { unsigned char *ctable=zdither_color_table; return ctable[_MIX(_DITH0(_R, r), _DITH0(_G, g),_DITH0(_B, b))]; } #endif #define DITHER_PIXEL2(a) \ { \ register int v,t,r,g,c; \ v=*(unsigned int *)(pp+(a)); \ g=(v & 0x07DF07DF) + g_d; \ r=(((v & 0xF800F800) >> 2) + r_d) & 0x70007000; \ t=r | g; \ c=ctable[t & 0xFFFF] | (ctable[t >> 16] << 8); \ *(unsigned short *)(dest+(a))=c; \ } /* NOTE: all the memory access are 16 bit aligned, so if buf or linesize are not multiple of 2, it cannot work efficiently (or hang!) */ void ZB_ditherFrameBuffer(ZBuffer *zb,unsigned char *buf, int linesize) { int xk,yk,x,y,c1,c2; unsigned char *dest1; unsigned short *pp1; int r_d,g_d,b_d; unsigned char *ctable=zb->dctable; register unsigned char *dest; register unsigned short *pp; assert( ((long)buf & 1) == 0 && (linesize & 1) == 0); for(yk=0;yk<4;yk++) { for(xk=0;xk<4;xk+=2) { #if BYTE_ORDER == BIG_ENDIAN c1=kernel8[yk*4+xk+1]; c2=kernel8[yk*4+xk]; #else c1=kernel8[yk*4+xk]; c2=kernel8[yk*4+xk+1]; #endif r_d=((c1 << 2) & 0xF800) >> 2; g_d=(c1 >> 4) & 0x07C0; b_d=(c1 >> 9) & 0x001F; r_d|=(((c2 << 2) & 0xF800) >> 2) << 16; g_d|=((c2 >> 4) & 0x07C0) << 16; b_d|=((c2 >> 9) & 0x001F) << 16; g_d=b_d | g_d; dest1=buf + (yk * linesize) + xk; pp1=zb->pbuf + (yk * zb->xsize) + xk; for(y=yk;y<zb->ysize;y+=4) { dest=dest1; pp=pp1; for(x=xk;x<zb->xsize;x+=16) { DITHER_PIXEL2(0); DITHER_PIXEL2(1*4); DITHER_PIXEL2(2*4); DITHER_PIXEL2(3*4); pp+=16; dest+=16; } dest1+=linesize*4; pp1+=zb->xsize*4; } } } } #endif