ref: 2298e130a5cf4bbf8d828cca6ed3902da8faaa83
dir: /src/zdither.c/
/*
* Highly optimised dithering 16 bits -> 8 bits.
* The formulas were taken in Mesa (Bob Mercier mercier@hollywood.cinenet.net).
*/
#include "../include/zbuffer.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.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 GLint 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, GLint nb_colors, GLubyte* color_indexes, GLint* color_table) {
GLint 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(GLint));
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(GLint r,GLint g,GLint b)
{
GLubyte *ctable=zdither_color_table;
return ctable[_MIX(_DITH0(_R, r), _DITH0(_G, g),_DITH0(_B, b))];
}
#endif
#define DITHER_PIXEL2(a) \
{ \
register GLint v, t, r, g, c; \
v = *(GLuint*)(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); \
*(GLushort*)(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, GLubyte* buf, GLint linesize) {
GLint xk, yk, x, y, c1, c2;
GLubyte* dest1;
GLushort* pp1;
GLint r_d, g_d, b_d;
GLubyte* ctable = zb->dctable;
register GLubyte* dest;
register GLushort* 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;
// NOTE BY GEK: The following line was modified to fix a compiler warning,
// casting zb->pbuf to GLushort*
pp1 = (GLushort*)(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