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greg |
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/* Copyright (c) 1989 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* colortab.c - 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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#include "color.h"
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#define NULL 0
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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 18
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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 frame buffer depth */
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#define FBDEPTH 8
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/* color map resolution */
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#define MAPSIZ 128
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/* map a color */
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#define map_col(c,p) clrmap[p][ colval(c,p)<1. ? \
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(int)(colval(c,p)*MAPSIZ) : MAPSIZ-1 ]
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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_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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COLR clrtab[1<<FBDEPTH];
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/* our color correction map */
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static BYTE clrmap[3][MAPSIZ];
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/* histogram of colors used */
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static unsigned histo[NRED][NGRN][NBLU];
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/* initial color cube boundaries */
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static int CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU};
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/* color cube partition */
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static CNODE ctree[1<<(FBDEPTH+1)];
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COLR *
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get_ctab(ncolors) /* assign a color table with max ncolors */
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int ncolors;
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{
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if (ncolors < 1 || ncolors > 1<<FBDEPTH)
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return(NULL);
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/* partition color table */
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cut(ctree, FBDEPTH, CLRCUBE, 0, ncolors);
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/* clear histogram */
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bzero(histo, sizeof(histo));
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/* return color table */
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return(clrtab);
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}
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int
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get_pixel(col) /* get pixel for color */
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COLOR col;
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{
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int cv[3];
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register CNODE *tp;
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register int h;
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/* map color */
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cv[RED] = map_col(col,RED);
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cv[GRN] = map_col(col,GRN);
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cv[BLU] = map_col(col,BLU);
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/* add to histogram */
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histo[cv[RED]][cv[GRN]][cv[BLU]]++;
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/* find pixel value in tree */
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tp = ctree;
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for (h = FBDEPTH; h > 0; h--) {
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if (is_pval(*tp))
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break;
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if (cv[prim(*tp)] < part(*tp))
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tp++; /* left branch */
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else
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tp += 1<<h; /* right branch */
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}
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#ifdef notdef
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printf("distance (%d,%d,%d)\n",
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cv[RED] - clrtab[pval(*tp)][RED]*NRED/256,
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cv[GRN] - clrtab[pval(*tp)][GRN]*NGRN/256,
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cv[BLU] - clrtab[pval(*tp)][BLU]*NBLU/256);
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#endif
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return(pval(*tp));
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}
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make_cmap(gam) /* make gamma correction map */
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double gam;
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{
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extern double pow();
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double d;
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register int i;
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for (i = 0; i < MAPSIZ; i++) {
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d = pow(i/(double)MAPSIZ, 1.0/gam);
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clrmap[RED][i] = d * NRED;
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clrmap[GRN][i] = d * NGRN;
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clrmap[BLU][i] = d * NBLU;
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}
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}
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static
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cut(tree, height, box, c0, c1) /* partition color space */
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register CNODE *tree;
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int height;
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register int box[3][2];
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int c0, c1;
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{
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int kb[3][2];
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if (c1-c0 == 1) { /* assign color */
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clrtab[c0][RED] = ((box[RED][0]+box[RED][1])<<7)/NRED;
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clrtab[c0][GRN] = ((box[GRN][0]+box[GRN][1])<<7)/NGRN;
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clrtab[c0][BLU] = ((box[BLU][0]+box[BLU][1])<<7)/NBLU;
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clrtab[c0][EXP] = COLXS;
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*tree = set_pval(c0);
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#ifdef notdef
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printf("final box size = (%d,%d,%d)\n",
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box[RED][1] - box[RED][0],
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box[GRN][1] - box[GRN][0],
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box[BLU][1] - box[BLU][0]);
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#endif
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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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bcopy(box, kb, sizeof(kb));
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kb[prim(*tree)][1] = part(*tree);
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cut(tree+1, height-1, kb, c0, (c0+c1)>>1); /* lesser */
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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<<height), height-1, kb, (c0+c1)>>1, c1); /* greater */
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}
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static int
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split(box) /* find median cut for box */
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register int box[3][2];
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{
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#define c0 r
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register int r, g, b;
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int pri;
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int 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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