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