Panda3D
zdither.cxx
1 /*
2  * Highly optimised dithering 16 bits -> 8 bits.
3  * The formulas were taken in Mesa (Bob Mercier mercier@hollywood.cinenet.net).
4  */
5 
6 #include <stdlib.h>
7 #include <stdio.h>
8 #include "zbuffer.h"
9 #include <assert.h>
10 
11 #if defined(TGL_FEATURE_8_BITS)
12 
13 #define _R 5
14 #define _G 9
15 #define _B 5
16 #define _DX 4
17 #define _DY 4
18 #define _D (_DX*_DY)
19 #define _MIX(r,g,b) ( ((g)<<6) | ((b)<<3) | (r) )
20 
21 #define DITHER_TABLE_SIZE (1 << 15)
22 
23 #define DITHER_INDEX(r,g,b) ((b) + (g) * _B + (r) * (_B * _G))
24 
25 #define MAXC 256
26 static int kernel8[_DY*_DX] = {
27  0 * MAXC, 8 * MAXC, 2 * MAXC, 10 * MAXC,
28  12 * MAXC, 4 * MAXC, 14 * MAXC, 6 * MAXC,
29  3 * MAXC, 11 * MAXC, 1 * MAXC, 9 * MAXC,
30  15 * MAXC, 7 * MAXC, 13 * MAXC, 5 * MAXC,
31 };
32 
33 /* we build the color table and the lookup table */
34 
35 void ZB_initDither(ZBuffer *zb,int nb_colors,
36  unsigned char *color_indexes,int *color_table)
37 {
38  int c,r,g,b,i,index,r1,g1,b1;
39 
40  if (nb_colors < (_R * _G * _B)) {
41  fprintf(stderr,"zdither: not enough colors\n");
42  exit(1);
43  }
44 
45  for(i=0;i<nb_colors;i++) color_table[i]=0;
46 
47  zb->nb_colors=nb_colors;
48  zb->ctable=gl_malloc(nb_colors * sizeof(int));
49 
50  for (r = 0; r < _R; r++) {
51  for (g = 0; g < _G; g++) {
52  for (b = 0; b < _B; b++) {
53  r1=(r*255) / (_R - 1);
54  g1=(g*255) / (_G - 1);
55  b1=(b*255) / (_B - 1);
56  index=DITHER_INDEX(r,g,b);
57  c=(r1 << 16) | (g1 << 8) | b1;
58  zb->ctable[index]=c;
59  color_table[index]=c;
60  }
61  }
62  }
63 
64  zb->dctable=gl_malloc( DITHER_TABLE_SIZE );
65 
66  for(i=0;i<DITHER_TABLE_SIZE;i++) {
67  r=(i >> 12) & 0x7;
68  g=(i >> 8) & 0xF;
69  b=(i >> 3) & 0x7;
70  index=DITHER_INDEX(r,g,b);
71  zb->dctable[i]=color_indexes[index];
72  }
73 }
74 
75 void
76 ZB_closeDither(ZBuffer *zb) {
77  gl_free(zb->ctable);
78  gl_free(zb->dctable);
79 }
80 
81 #if 0
82 int
83 ZDither_lookupColor(int r,int g,int b) {
84  unsigned char *ctable=zdither_color_table;
85  return ctable[_MIX(_DITH0(_R, r), _DITH0(_G, g),_DITH0(_B, b))];
86 }
87 #endif
88 
89 
90 #define DITHER_PIXEL2(a) \
91 { \
92  int v,t,r,g,c; \
93  v=*(unsigned int *)(pp+(a)); \
94  g=(v & 0x07DF07DF) + g_d; \
95  r=(((v & 0xF800F800) >> 2) + r_d) & 0x70007000; \
96  t=r | g; \
97  c=ctable[t & 0xFFFF] | (ctable[t >> 16] << 8); \
98  *(unsigned short *)(dest+(a))=c; \
99 }
100 
101 /* NOTE: all the memory access are 16 bit aligned, so if buf or
102  linesize are not multiple of 2, it cannot work efficiently (or
103  hang!) */
104 
105 void
106 ZB_ditherFrameBuffer(ZBuffer *zb,unsigned char *buf,
107  int linesize) {
108  int xk,yk,x,y,c1,c2;
109  unsigned char *dest1;
110  unsigned short *pp1;
111  int r_d,g_d,b_d;
112  unsigned char *ctable=zb->dctable;
113  unsigned char *dest;
114  unsigned short *pp;
115 
116  assert( ((long)buf & 1) == 0 && (linesize & 1) == 0);
117 
118  for(yk=0;yk<4;yk++) {
119  for(xk=0;xk<4;xk+=2) {
120 #if BYTE_ORDER == BIG_ENDIAN
121  c1=kernel8[yk*4+xk+1];
122  c2=kernel8[yk*4+xk];
123 #else
124  c1=kernel8[yk*4+xk];
125  c2=kernel8[yk*4+xk+1];
126 #endif
127  r_d=((c1 << 2) & 0xF800) >> 2;
128  g_d=(c1 >> 4) & 0x07C0;
129  b_d=(c1 >> 9) & 0x001F;
130 
131  r_d|=(((c2 << 2) & 0xF800) >> 2) << 16;
132  g_d|=((c2 >> 4) & 0x07C0) << 16;
133  b_d|=((c2 >> 9) & 0x001F) << 16;
134  g_d=b_d | g_d;
135 
136  dest1=buf + (yk * linesize) + xk;
137  pp1=zb->pbuf + (yk * zb->xsize) + xk;
138 
139  for(y=yk;y<zb->ysize;y+=4) {
140  dest=dest1;
141  pp=pp1;
142  for(x=xk;x<zb->xsize;x+=16) {
143 
144  DITHER_PIXEL2(0);
145  DITHER_PIXEL2(1*4);
146  DITHER_PIXEL2(2*4);
147  DITHER_PIXEL2(3*4);
148 
149  pp+=16;
150  dest+=16;
151  }
152  dest1+=linesize*4;
153  pp1+=zb->xsize*4;
154  }
155  }
156  }
157 }
158 
159 #endif