| 1 |
greg |
2.4 |
/* Copyright (c) 1993 Regents of the University of California */
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greg |
2.1 |
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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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* Simple median-cut color quantization based on colortab.c
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*/
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#include "standard.h"
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#include "color.h"
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/* histogram resolution */
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#define NRED 36
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#define NGRN 48
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#define NBLU 24
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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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/* color partition */
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#define set_branch(p,c) ((c)<<2|(p))
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#define part(cn) ((cn)>>2)
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#define prim(cn) ((cn)&3)
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/* our color table (global) */
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BYTE clrtab[256][3];
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/* histogram of colors / color assignments */
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static unsigned histo[NRED][NGRN][NBLU];
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#define cndx(c) histo[((c)[RED]*NRED)>>8][((c)[GRN]*NGRN)>>8][((c)[BLU]*NBLU)>>8]
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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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/* maximum propagated error during dithering */
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#define MAXERR 20
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greg |
2.2 |
/* define CLOSEST to get closest colors */
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greg |
2.4 |
#ifndef CLOSEST
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#ifdef SPEED
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#if SPEED > 8
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#define CLOSEST 1 /* this step takes a little longer */
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#endif
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#endif
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#endif
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greg |
2.1 |
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new_histo() /* clear our histogram */
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{
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bzero((char *)histo, sizeof(histo));
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}
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cnt_pixel(col) /* add pixel to our histogram */
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register BYTE col[];
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{
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cndx(col)++;
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}
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cnt_colrs(cs, n) /* add a scanline to our histogram */
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register COLR *cs;
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register int n;
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{
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while (n-- > 0) {
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cndx(cs[0])++;
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cs++;
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}
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}
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new_clrtab(ncolors) /* make new color table using ncolors */
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int ncolors;
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{
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if (ncolors < 1)
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return(0);
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if (ncolors > 256)
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ncolors = 256;
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/* partition color space */
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cut(CLRCUBE, 0, ncolors);
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greg |
2.2 |
#ifdef CLOSEST
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closest(ncolors); /* ensure colors picked are closest */
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#endif
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greg |
2.1 |
/* return new color table size */
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return(ncolors);
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}
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int
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map_pixel(col) /* get pixel for color */
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register BYTE col[];
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{
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return(cndx(col));
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}
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map_colrs(bs, cs, n) /* convert a scanline to color index values */
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register BYTE *bs;
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register COLR *cs;
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register int n;
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{
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while (n-- > 0) {
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*bs++ = cndx(cs[0]);
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cs++;
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}
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}
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dith_colrs(bs, cs, n) /* convert scanline to dithered index values */
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register BYTE *bs;
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register COLR *cs;
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int n;
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{
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static short (*cerr)[3];
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static int N = 0;
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int err[3], errp[3];
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register int x, i;
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if (n != N) { /* get error propogation array */
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if (N)
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cerr = (short (*)[3])realloc((char *)cerr,
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3*n*sizeof(short));
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else
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cerr = (short (*)[3])malloc(3*n*sizeof(short));
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if (cerr == NULL) {
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N = 0;
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map_colrs(bs, cs, n);
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return;
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}
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N = n;
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bzero((char *)cerr, 3*N*sizeof(short));
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}
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err[0] = err[1] = err[2] = 0;
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for (x = 0; x < n; x++) {
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for (i = 0; i < 3; i++) { /* dither value */
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errp[i] = err[i];
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err[i] += cerr[x][i];
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#ifdef MAXERR
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if (err[i] > MAXERR) err[i] = MAXERR;
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else if (err[i] < -MAXERR) err[i] = -MAXERR;
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#endif
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err[i] += cs[x][i];
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if (err[i] < 0) err[i] = 0;
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else if (err[i] > 255) err[i] = 255;
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}
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bs[x] = cndx(err);
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for (i = 0; i < 3; i++) { /* propagate error */
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err[i] -= clrtab[bs[x]][i];
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err[i] /= 3;
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cerr[x][i] = err[i] + errp[i];
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}
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}
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}
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static
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cut(box, c0, c1) /* partition color space */
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register int box[3][2];
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int c0, c1;
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{
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register int branch;
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int kb[3][2];
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if (c1-c0 <= 1) { /* assign pixel */
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mktabent(c0, box);
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return;
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}
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/* split box */
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branch = split(box);
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bcopy((char *)box, (char *)kb, sizeof(kb));
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/* do left (lesser) branch */
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kb[prim(branch)][1] = part(branch);
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cut(kb, c0, (c0+c1)>>1);
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/* do right branch */
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kb[prim(branch)][0] = part(branch);
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kb[prim(branch)][1] = box[prim(branch)][1];
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cut(kb, (c0+c1)>>1, c1);
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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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greg |
2.6 |
long t[HMAX], med;
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greg |
2.1 |
/* 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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| 218 |
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med += t[b];
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}
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break;
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| 221 |
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}
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| 222 |
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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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| 224 |
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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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| 231 |
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#undef c0
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| 232 |
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}
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| 233 |
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| 234 |
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| 235 |
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static
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mktabent(p, box) /* compute average color for box and assign */
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| 237 |
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int p;
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| 238 |
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register int box[3][2];
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| 239 |
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{
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| 240 |
greg |
2.5 |
unsigned long sum[3];
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| 241 |
greg |
2.7 |
unsigned r, g;
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| 242 |
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unsigned long n;
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| 243 |
greg |
2.5 |
register unsigned b, c;
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| 244 |
greg |
2.1 |
/* sum pixels in box */
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| 245 |
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n = 0;
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| 246 |
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sum[RED] = sum[GRN] = sum[BLU] = 0;
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| 247 |
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for (r = box[RED][0]; r < box[RED][1]; r++)
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| 248 |
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for (g = box[GRN][0]; g < box[GRN][1]; g++)
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| 249 |
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for (b = box[BLU][0]; b < box[BLU][1]; b++) {
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| 250 |
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if (c = histo[r][g][b]) {
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| 251 |
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n += c;
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| 252 |
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sum[RED] += (long)c*r;
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| 253 |
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sum[GRN] += (long)c*g;
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| 254 |
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sum[BLU] += (long)c*b;
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| 255 |
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}
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| 256 |
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histo[r][g][b] = p; /* assign pixel */
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| 257 |
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}
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| 258 |
greg |
2.7 |
if (n >= (1L<<23)/HMAX) { /* avoid overflow */
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| 259 |
greg |
2.5 |
sum[RED] /= n;
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| 260 |
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sum[GRN] /= n;
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| 261 |
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sum[BLU] /= n;
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| 262 |
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n = 1;
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| 263 |
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}
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| 264 |
greg |
2.1 |
if (n) { /* compute average */
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| 265 |
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clrtab[p][RED] = sum[RED]*256/NRED/n;
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| 266 |
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clrtab[p][GRN] = sum[GRN]*256/NGRN/n;
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| 267 |
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clrtab[p][BLU] = sum[BLU]*256/NBLU/n;
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| 268 |
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} else { /* empty box -- use midpoint */
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| 269 |
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clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2;
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| 270 |
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clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2;
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| 271 |
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clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2;
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| 272 |
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}
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| 273 |
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}
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| 274 |
greg |
2.2 |
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| 275 |
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| 276 |
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#ifdef CLOSEST
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| 277 |
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#define NBSIZ 32
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| 278 |
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static
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| 279 |
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closest(n) /* make sure we have the closest colors */
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| 280 |
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int n;
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| 281 |
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{
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| 282 |
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BYTE *neigh[256];
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| 283 |
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register int r, g, b;
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| 284 |
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#define i r
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| 285 |
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/* get space for neighbor lists */
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| 286 |
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for (i = 0; i < n; i++) {
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| 287 |
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if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) {
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| 288 |
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while (i--)
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| 289 |
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free(neigh[i]);
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| 290 |
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return; /* ENOMEM -- abandon effort */
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| 291 |
|
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}
|
| 292 |
|
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neigh[i][0] = i; /* identity is terminator */
|
| 293 |
|
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}
|
| 294 |
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/* make neighbor lists */
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| 295 |
greg |
2.3 |
for (r = 0; r < NRED; r++)
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| 296 |
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for (g = 0; g < NGRN; g++)
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| 297 |
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for (b = 0; b < NBLU; b++) {
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| 298 |
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if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b])
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| 299 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
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| 300 |
greg |
2.3 |
if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b])
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| 301 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
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| 302 |
greg |
2.3 |
if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1])
|
| 303 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r][g][b+1]);
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| 304 |
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}
|
| 305 |
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/* assign closest values */
|
| 306 |
|
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for (r = 0; r < NRED; r++)
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| 307 |
|
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for (g = 0; g < NGRN; g++)
|
| 308 |
|
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for (b = 0; b < NBLU; b++)
|
| 309 |
|
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setclosest(neigh, r, g, b);
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| 310 |
|
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/* free neighbor lists */
|
| 311 |
|
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for (i = 0; i < n; i++)
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| 312 |
|
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free(neigh[i]);
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| 313 |
|
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#undef i
|
| 314 |
|
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}
|
| 315 |
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| 316 |
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|
| 317 |
|
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static
|
| 318 |
|
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addneigh(nl, i, j) /* i and j are neighbors; add them to list */
|
| 319 |
|
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register BYTE *nl[];
|
| 320 |
|
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register int i;
|
| 321 |
|
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int j;
|
| 322 |
|
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{
|
| 323 |
|
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int nc;
|
| 324 |
|
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char *nnl;
|
| 325 |
|
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register int t;
|
| 326 |
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|
| 327 |
|
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for (nc = 0; nc < 2; nc++) { /* do both neighbors */
|
| 328 |
|
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for (t = 0; nl[i][t] != i; t++)
|
| 329 |
|
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if (nl[i][t] == j)
|
| 330 |
|
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break; /* in list already */
|
| 331 |
|
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if (nl[i][t] == i) { /* add to list */
|
| 332 |
|
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nl[i][t++] = j;
|
| 333 |
|
|
if (t % NBSIZ == 0) { /* enlarge list */
|
| 334 |
|
|
if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL)
|
| 335 |
|
|
t--;
|
| 336 |
|
|
else
|
| 337 |
|
|
nl[i] = (BYTE *)nnl;
|
| 338 |
|
|
}
|
| 339 |
|
|
nl[i][t] = i; /* terminator */
|
| 340 |
|
|
}
|
| 341 |
|
|
t = i; i = j; j = t; /* swap and do it again */
|
| 342 |
|
|
}
|
| 343 |
|
|
}
|
| 344 |
|
|
|
| 345 |
|
|
|
| 346 |
|
|
static unsigned
|
| 347 |
|
|
dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */
|
| 348 |
|
|
register BYTE col[3];
|
| 349 |
|
|
int r, g, b;
|
| 350 |
|
|
{
|
| 351 |
greg |
2.4 |
register int tmp;
|
| 352 |
greg |
2.2 |
register unsigned sum;
|
| 353 |
|
|
|
| 354 |
|
|
tmp = col[RED]*NRED/256 - r;
|
| 355 |
|
|
sum = tmp*tmp;
|
| 356 |
|
|
tmp = col[GRN]*NGRN/256 - g;
|
| 357 |
|
|
sum += tmp*tmp;
|
| 358 |
|
|
tmp = col[BLU]*NBLU/256 - b;
|
| 359 |
|
|
sum += tmp*tmp;
|
| 360 |
|
|
return(sum);
|
| 361 |
|
|
}
|
| 362 |
|
|
|
| 363 |
|
|
|
| 364 |
|
|
static
|
| 365 |
|
|
setclosest(nl, r, g, b) /* find index closest to color and assign */
|
| 366 |
|
|
BYTE *nl[];
|
| 367 |
|
|
int r, g, b;
|
| 368 |
|
|
{
|
| 369 |
|
|
int ident;
|
| 370 |
|
|
unsigned min;
|
| 371 |
|
|
register unsigned d;
|
| 372 |
|
|
register BYTE *p;
|
| 373 |
|
|
/* get starting value */
|
| 374 |
|
|
min = dist(clrtab[ident=histo[r][g][b]], r, g, b);
|
| 375 |
|
|
/* find minimum */
|
| 376 |
|
|
for (p = nl[ident]; *p != ident; p++)
|
| 377 |
|
|
if ((d = dist(clrtab[*p], r, g, b)) < min) {
|
| 378 |
|
|
min = d;
|
| 379 |
|
|
histo[r][g][b] = *p;
|
| 380 |
|
|
}
|
| 381 |
|
|
}
|
| 382 |
|
|
#endif
|
