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#ifndef lint
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static const char RCSid[] = "$Id: rhd_ctab.c,v 3.6 2011/05/20 02:06:39 greg Exp $";
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#endif
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/*
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* Allocate and control dynamic color table.
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*
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* We start off with a uniform partition of color space.
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* As pixels are sent to the frame buffer, a histogram is built.
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* When a new color table is requested, the histogram is used
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* to make a pseudo-optimal partition, after which the
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* histogram is cleared. This algorithm
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* performs only as well as the next drawing's color
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* distribution is correlated to the last.
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*
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* This module is essentially identical to src/rt/colortab.c,
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* except there is no color mapping, since the tm library is used.
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*/
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#include <string.h>
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#include "standard.h"
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#include "rhdisp.h"
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#include "color.h"
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/* histogram resolution */
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#define NRED 24
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#define NGRN 32
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#define NBLU 16
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#define HMAX NGRN
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/* minimum box count for adaptive partition */
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#define MINSAMP 7
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/* maximum distance^2 before color reassign */
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#define MAXDST2 12
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/* color partition tree */
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#define CNODE short
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#define set_branch(p,c) ((c)<<2|(p))
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#define set_pval(pv) ((pv)<<2|3)
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#define is_branch(cn) (((cn)&3)!=3)
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#define is_pval(cn) (((cn)&3)==3)
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#define part(cn) ((cn)>>2)
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#define prim(cn) ((cn)&3)
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#define pval(cn) ((cn)>>2)
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/* our color table */
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static struct tabent {
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long sum[3]; /* sum of colors using this entry */
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int n; /* number of colors */
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uby8 ent[3]; /* current table value */
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} *clrtab = NULL;
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/* color cube partition */
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static CNODE *ctree = NULL;
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/* histogram of colors used */
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static unsigned short histo[NRED][NGRN][NBLU];
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/* initial color cube boundary */
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static int CLRCUBE[3][2] = {{0,NRED},{0,NGRN},{0,NBLU}};
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static void cut(CNODE *tree, int level, int box[3][2], int c0, int c1);
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static int split(int box[3][2]);
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int
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new_ctab( /* start new color table with max ncolors */
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int ncolors
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)
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{
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int treesize;
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if (ncolors < 1)
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return(0);
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/* free old tables */
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if (clrtab != NULL)
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free((void *)clrtab);
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if (ctree != NULL)
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free((void *)ctree);
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/* get new tables */
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for (treesize = 1; treesize < ncolors; treesize <<= 1)
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;
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treesize <<= 1;
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clrtab = (struct tabent *)calloc(ncolors, sizeof(struct tabent));
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ctree = (CNODE *)malloc(treesize*sizeof(CNODE));
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if (clrtab == NULL || ctree == NULL)
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return(0);
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/* partition color space */
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cut(ctree, 0, CLRCUBE, 0, ncolors);
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/* clear histogram */
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memset((void *)histo, '\0', sizeof(histo));
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/* return number of colors used */
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return(ncolors);
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}
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int
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get_pixel( /* get pixel for color */
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uby8 rgb[3],
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void (*set_pixel)(int h, int r, int g, int b)
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)
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{
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int r, g, b;
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int cv[3];
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CNODE *tp;
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int h;
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/* get desired color */
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r = rgb[RED];
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g = rgb[GRN];
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b = rgb[BLU];
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/* reduce resolution */
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cv[RED] = (r*NRED)>>8;
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cv[GRN] = (g*NGRN)>>8;
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cv[BLU] = (b*NBLU)>>8;
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/* add to histogram */
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histo[cv[RED]][cv[GRN]][cv[BLU]]++;
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/* find pixel in tree */
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for (tp = ctree, h = 0; is_branch(*tp); h++)
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if (cv[prim(*tp)] < part(*tp))
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tp += 1<<h; /* left branch */
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else
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tp += 1<<(h+1); /* right branch */
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h = pval(*tp);
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/* add to color table */
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clrtab[h].sum[RED] += r;
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clrtab[h].sum[GRN] += g;
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clrtab[h].sum[BLU] += b;
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clrtab[h].n++;
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/* recompute average */
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r = clrtab[h].sum[RED] / clrtab[h].n;
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g = clrtab[h].sum[GRN] / clrtab[h].n;
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b = clrtab[h].sum[BLU] / clrtab[h].n;
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/* check for movement */
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if (clrtab[h].n == 1 ||
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(r-clrtab[h].ent[RED])*(r-clrtab[h].ent[RED]) +
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(g-clrtab[h].ent[GRN])*(g-clrtab[h].ent[GRN]) +
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(b-clrtab[h].ent[BLU])*(b-clrtab[h].ent[BLU]) > MAXDST2) {
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clrtab[h].ent[RED] = r;
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clrtab[h].ent[GRN] = g; /* reassign pixel */
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clrtab[h].ent[BLU] = b;
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#ifdef DEBUG
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{
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extern char errmsg[];
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sprintf(errmsg, "pixel %d = (%d,%d,%d) (%d refs)\n",
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h, r, g, b, clrtab[h].n);
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eputs(errmsg);
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}
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#endif
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(*set_pixel)(h, r, g, b);
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}
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return(h); /* return pixel value */
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}
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static void
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cut( /* partition color space */
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CNODE *tree,
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int level,
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int box[3][2],
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int c0,
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int c1
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)
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{
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int kb[3][2];
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if (c1-c0 <= 1) { /* assign pixel */
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*tree = set_pval(c0);
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return;
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}
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/* split box */
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*tree = split(box);
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memcpy((void *)kb, (void *)box, sizeof(kb));
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/* do left (lesser) branch */
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kb[prim(*tree)][1] = part(*tree);
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cut(tree+(1<<level), level+1, kb, c0, (c0+c1)>>1);
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/* do right branch */
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kb[prim(*tree)][0] = part(*tree);
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kb[prim(*tree)][1] = box[prim(*tree)][1];
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cut(tree+(1<<(level+1)), level+1, kb, (c0+c1)>>1, c1);
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}
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static int
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split( /* find median cut for box */
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int box[3][2]
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)
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{
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#define c0 r
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int r, g, b;
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int pri;
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long t[HMAX], med;
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/* find dominant axis */
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pri = RED;
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if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
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pri = GRN;
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if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
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pri = BLU;
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/* sum histogram over box */
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med = 0;
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switch (pri) {
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case RED:
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for (r = box[RED][0]; r < box[RED][1]; r++) {
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t[r] = 0;
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for (g = box[GRN][0]; g < box[GRN][1]; g++)
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for (b = box[BLU][0]; b < box[BLU][1]; b++)
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t[r] += histo[r][g][b];
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med += t[r];
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}
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break;
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case GRN:
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for (g = box[GRN][0]; g < box[GRN][1]; g++) {
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t[g] = 0;
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for (b = box[BLU][0]; b < box[BLU][1]; b++)
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for (r = box[RED][0]; r < box[RED][1]; r++)
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t[g] += histo[r][g][b];
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med += t[g];
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}
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break;
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case BLU:
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for (b = box[BLU][0]; b < box[BLU][1]; b++) {
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t[b] = 0;
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for (r = box[RED][0]; r < box[RED][1]; r++)
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for (g = box[GRN][0]; g < box[GRN][1]; g++)
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t[b] += histo[r][g][b];
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med += t[b];
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}
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break;
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}
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if (med < MINSAMP) /* if too sparse, split at midpoint */
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return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
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/* find median position */
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med >>= 1;
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for (c0 = box[pri][0]; med > 0; c0++)
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med -= t[c0];
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if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */
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c0--; /* part left of median */
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return(set_branch(pri,c0));
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#undef c0
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}
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