Panda3D

zdither.cxx

00001 /* 
00002  * Highly optimised dithering 16 bits -> 8 bits. 
00003  * The formulas were taken in Mesa (Bob Mercier mercier@hollywood.cinenet.net).
00004  */
00005 
00006 #include <stdlib.h>
00007 #include <stdio.h>
00008 #include "zbuffer.h"
00009 #include <assert.h>
00010 
00011 #if defined(TGL_FEATURE_8_BITS)
00012 
00013 #define _R  5
00014 #define _G  9
00015 #define _B  5
00016 #define _DX 4
00017 #define _DY 4
00018 #define _D  (_DX*_DY)
00019 #define _MIX(r,g,b) ( ((g)<<6) | ((b)<<3) | (r) )
00020 
00021 #define DITHER_TABLE_SIZE (1 << 15)
00022 
00023 #define DITHER_INDEX(r,g,b) ((b) + (g) * _B + (r) * (_B * _G))
00024 
00025 #define MAXC    256
00026 static int kernel8[_DY*_DX] = {
00027     0 * MAXC,  8 * MAXC,  2 * MAXC, 10 * MAXC,
00028    12 * MAXC,  4 * MAXC, 14 * MAXC,  6 * MAXC,
00029     3 * MAXC, 11 * MAXC,  1 * MAXC,  9 * MAXC,
00030    15 * MAXC,  7 * MAXC, 13 * MAXC,  5 * MAXC,
00031 };
00032 
00033 /* we build the color table and the lookup table */
00034 
00035 void ZB_initDither(ZBuffer *zb,int nb_colors,
00036                    unsigned char *color_indexes,int *color_table)
00037 {
00038   int c,r,g,b,i,index,r1,g1,b1;
00039 
00040   if (nb_colors < (_R * _G * _B)) {
00041     fprintf(stderr,"zdither: not enough colors\n");
00042     exit(1);
00043   }
00044 
00045   for(i=0;i<nb_colors;i++) color_table[i]=0;
00046 
00047   zb->nb_colors=nb_colors;
00048   zb->ctable=gl_malloc(nb_colors * sizeof(int));
00049 
00050   for (r = 0; r < _R; r++) {
00051     for (g = 0; g < _G; g++) {
00052       for (b = 0; b < _B; b++) {
00053     r1=(r*255) / (_R - 1);
00054     g1=(g*255) / (_G - 1);
00055     b1=(b*255) / (_B - 1);
00056     index=DITHER_INDEX(r,g,b);
00057     c=(r1 << 16) | (g1 << 8) | b1;
00058     zb->ctable[index]=c;
00059     color_table[index]=c;
00060       }
00061     }
00062   }
00063 
00064   zb->dctable=gl_malloc( DITHER_TABLE_SIZE );
00065 
00066   for(i=0;i<DITHER_TABLE_SIZE;i++) {
00067     r=(i >> 12) & 0x7;
00068     g=(i >> 8) & 0xF;
00069     b=(i >> 3) & 0x7;
00070     index=DITHER_INDEX(r,g,b);
00071     zb->dctable[i]=color_indexes[index];
00072   }
00073 }
00074 
00075 void
00076 ZB_closeDither(ZBuffer *zb) {
00077   gl_free(zb->ctable);
00078   gl_free(zb->dctable);
00079 }
00080 
00081 #if 0
00082 int
00083 ZDither_lookupColor(int r,int g,int b) {
00084   unsigned char *ctable=zdither_color_table;
00085   return ctable[_MIX(_DITH0(_R, r), _DITH0(_G, g),_DITH0(_B, b))];
00086 }
00087 #endif
00088 
00089 
00090 #define DITHER_PIXEL2(a)            \
00091 { \
00092   register int v,t,r,g,c;           \
00093   v=*(unsigned int *)(pp+(a));                  \
00094   g=(v & 0x07DF07DF) + g_d; \
00095   r=(((v & 0xF800F800) >> 2) + r_d) & 0x70007000; \
00096   t=r | g; \
00097   c=ctable[t & 0xFFFF] | (ctable[t >> 16] << 8); \
00098   *(unsigned short *)(dest+(a))=c;  \
00099 }
00100 
00101 /* NOTE: all the memory access are 16 bit aligned, so if buf or
00102    linesize are not multiple of 2, it cannot work efficiently (or
00103    hang!) */
00104 
00105 void
00106 ZB_ditherFrameBuffer(ZBuffer *zb,unsigned char *buf,
00107                      int linesize) {
00108   int xk,yk,x,y,c1,c2;
00109   unsigned char *dest1;
00110   unsigned short *pp1;
00111   int r_d,g_d,b_d;
00112   unsigned char *ctable=zb->dctable;
00113   register unsigned char *dest;
00114   register unsigned short *pp;
00115 
00116   assert( ((long)buf & 1) == 0 && (linesize & 1) == 0);
00117 
00118   for(yk=0;yk<4;yk++) {
00119     for(xk=0;xk<4;xk+=2) {
00120 #if BYTE_ORDER == BIG_ENDIAN
00121       c1=kernel8[yk*4+xk+1];
00122       c2=kernel8[yk*4+xk];
00123 #else
00124       c1=kernel8[yk*4+xk];
00125       c2=kernel8[yk*4+xk+1];
00126 #endif
00127       r_d=((c1 << 2) & 0xF800) >> 2;
00128       g_d=(c1 >> 4) & 0x07C0;
00129       b_d=(c1 >> 9) & 0x001F;
00130       
00131       r_d|=(((c2 << 2) & 0xF800) >> 2) << 16;
00132       g_d|=((c2 >> 4) & 0x07C0) << 16;
00133       b_d|=((c2 >> 9) & 0x001F) << 16;
00134       g_d=b_d | g_d;
00135 
00136       dest1=buf + (yk * linesize) + xk;
00137       pp1=zb->pbuf + (yk * zb->xsize) + xk;
00138       
00139       for(y=yk;y<zb->ysize;y+=4) {
00140         dest=dest1;
00141         pp=pp1;
00142         for(x=xk;x<zb->xsize;x+=16) {
00143 
00144           DITHER_PIXEL2(0);
00145           DITHER_PIXEL2(1*4);
00146           DITHER_PIXEL2(2*4);
00147           DITHER_PIXEL2(3*4);
00148 
00149           pp+=16;
00150           dest+=16;
00151         }
00152         dest1+=linesize*4;
00153         pp1+=zb->xsize*4;
00154       }
00155     }
00156   }
00157 }
00158 
00159 #endif
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