src/px/clrtab.c

/* Copyright (c) 1993 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Simple median-cut color quantization based on colortab.c
 */

#include "standard.h"

#include "color.h"
                                /* histogram resolution */
#define NRED            36
#define NGRN            48
#define NBLU            24
#define HMAX            NGRN
                                /* minimum box count for adaptive partition */
#define MINSAMP         7
                                /* color partition */
#define set_branch(p,c) ((c)<<2|(p))
#define part(cn)        ((cn)>>2)
#define prim(cn)        ((cn)&3)
                                /* our color table (global) */
extern BYTE     clrtab[256][3];
                                /* histogram of colors / color assignments */
static unsigned histo[NRED][NGRN][NBLU];
#define cndx(c)         histo[((c)[RED]*NRED)>>8][((c)[GRN]*NGRN)>>8][((c)[BLU]*NBLU)>>8]
                                /* initial color cube boundary */
static int      CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU};
                                /* maximum propagated error during dithering */
#define MAXERR          20
                                /* define CLOSEST to get closest colors */
#ifndef CLOSEST
#ifdef SPEED
#if  SPEED > 8
#define CLOSEST         1       /* this step takes a little longer */
#endif
#endif
#endif


new_histo(n)            /* clear our histogram */
int     n;
{
        bzero((char *)histo, sizeof(histo));
        return(0);
}


cnt_pixel(col)          /* add pixel to our histogram */
register BYTE   col[];
{
        cndx(col)++;
}


cnt_colrs(cs, n)                /* add a scanline to our histogram */
register COLR   *cs;
register int    n;
{
        while (n-- > 0) {
                cndx(cs[0])++;
                cs++;
        }
}


new_clrtab(ncolors)             /* make new color table using ncolors */
int     ncolors;
{
        if (ncolors < 1)
                return(0);
        if (ncolors > 256)
                ncolors = 256;
                                /* partition color space */
        cut(CLRCUBE, 0, ncolors);
#ifdef CLOSEST
        closest(ncolors);       /* ensure colors picked are closest */
#endif
                                /* reset dithering function */
        dith_colrs((BYTE *)NULL, (COLR *)NULL, 0);
                                /* return new color table size */
        return(ncolors);
}


int
map_pixel(col)                  /* get pixel for color */
register BYTE   col[];
{
    return(cndx(col));
}


map_colrs(bs, cs, n)            /* convert a scanline to color index values */
register BYTE   *bs;
register COLR   *cs;
register int    n;
{
        while (n-- > 0) {
                *bs++ = cndx(cs[0]);
                cs++;
        }
}


dith_colrs(bs, cs, n)           /* convert scanline to dithered index values */
register BYTE   *bs;
register COLR   *cs;
int     n;
{
        static short    (*cerr)[3] = NULL;
        static int      N = 0;
        int     err[3], errp[3];
        register int    x, i;

        if (n != N) {           /* get error propogation array */
                if (N) {
                        free((char *)cerr);
                        cerr = NULL;
                }
                if (n)
                        cerr = (short (*)[3])malloc(3*n*sizeof(short));
                if (cerr == NULL) {
                        N = 0;
                        map_colrs(bs, cs, n);
                        return;
                }
                N = n;
                bzero((char *)cerr, 3*N*sizeof(short));
        }
        err[0] = err[1] = err[2] = 0;
        for (x = 0; x < n; x++) {
                for (i = 0; i < 3; i++) {       /* dither value */
                        errp[i] = err[i];
                        err[i] += cerr[x][i];
#ifdef MAXERR
                        if (err[i] > MAXERR) err[i] = MAXERR;
                        else if (err[i] < -MAXERR) err[i] = -MAXERR;
#endif
                        err[i] += cs[x][i];
                        if (err[i] < 0) err[i] = 0;
                        else if (err[i] > 255) err[i] = 255;
                }
                bs[x] = cndx(err);
                for (i = 0; i < 3; i++) {       /* propagate error */
                        err[i] -= clrtab[bs[x]][i];
                        err[i] /= 3;
                        cerr[x][i] = err[i] + errp[i];
                }
        }
}


static
cut(box, c0, c1)                        /* partition color space */
register int    box[3][2];
int     c0, c1;
{
        register int    branch;
        int     kb[3][2];
        
        if (c1-c0 <= 1) {               /* assign pixel */
                mktabent(c0, box);
                return;
        }
                                        /* split box */
        branch = split(box);
        bcopy((char *)box, (char *)kb, sizeof(kb));
                                                /* do left (lesser) branch */
        kb[prim(branch)][1] = part(branch);
        cut(kb, c0, (c0+c1)>>1);
                                                /* do right branch */
        kb[prim(branch)][0] = part(branch);
        kb[prim(branch)][1] = box[prim(branch)][1];
        cut(kb, (c0+c1)>>1, c1);
}


static int
split(box)                              /* find median cut for box */
register int    box[3][2];
{
#define c0      r
        register int    r, g, b;
        int     pri;
        long    t[HMAX], med;
                                        /* find dominant axis */
        pri = RED;
        if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
                pri = GRN;
        if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
                pri = BLU;
                                        /* sum histogram over box */
        med = 0;
        switch (pri) {
        case RED:
                for (r = box[RED][0]; r < box[RED][1]; r++) {
                        t[r] = 0;
                        for (g = box[GRN][0]; g < box[GRN][1]; g++)
                                for (b = box[BLU][0]; b < box[BLU][1]; b++)
                                        t[r] += histo[r][g][b];
                        med += t[r];
                }
                break;
        case GRN:
                for (g = box[GRN][0]; g < box[GRN][1]; g++) {
                        t[g] = 0;
                        for (b = box[BLU][0]; b < box[BLU][1]; b++)
                                for (r = box[RED][0]; r < box[RED][1]; r++)
                                        t[g] += histo[r][g][b];
                        med += t[g];
                }
                break;
        case BLU:
                for (b = box[BLU][0]; b < box[BLU][1]; b++) {
                        t[b] = 0;
                        for (r = box[RED][0]; r < box[RED][1]; r++)
                                for (g = box[GRN][0]; g < box[GRN][1]; g++)
                                        t[b] += histo[r][g][b];
                        med += t[b];
                }
                break;
        }
        if (med < MINSAMP)              /* if too sparse, split at midpoint */
                return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
                                        /* find median position */
        med >>= 1;
        for (c0 = box[pri][0]; med > 0; c0++)
                med -= t[c0];
        if (c0 > (box[pri][0]+box[pri][1])>>1)  /* if past the midpoint */
                c0--;                           /* part left of median */
        return(set_branch(pri,c0));
#undef c0
}


static
mktabent(p, box)        /* compute average color for box and assign */
int     p;
register int    box[3][2];
{
        unsigned long   sum[3];
        unsigned        r, g;
        unsigned long   n;
        register unsigned       b, c;
                                                /* sum pixels in box */
        n = 0;
        sum[RED] = sum[GRN] = sum[BLU] = 0;
        for (r = box[RED][0]; r < box[RED][1]; r++)
            for (g = box[GRN][0]; g < box[GRN][1]; g++)
                for (b = box[BLU][0]; b < box[BLU][1]; b++) {
                    if (c = histo[r][g][b]) {
                        n += c;
                        sum[RED] += (long)c*r;
                        sum[GRN] += (long)c*g;
                        sum[BLU] += (long)c*b;
                    }
                    histo[r][g][b] = p;         /* assign pixel */
                }
        if (n >= (1L<<23)/HMAX) {               /* avoid overflow */
                sum[RED] /= n;
                sum[GRN] /= n;
                sum[BLU] /= n;
                n = 1;
        }
        if (n) {                                /* compute average */
                clrtab[p][RED] = sum[RED]*256/NRED/n;
                clrtab[p][GRN] = sum[GRN]*256/NGRN/n;
                clrtab[p][BLU] = sum[BLU]*256/NBLU/n;
        } else {                                /* empty box -- use midpoint */
                clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2;
                clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2;
                clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2;
        }
}


#ifdef CLOSEST
#define NBSIZ           32
static
closest(n)                      /* make sure we have the closest colors */
int     n;
{
        BYTE    *neigh[256];
        register int    r, g, b;
#define i r
                                        /* get space for neighbor lists */
        for (i = 0; i < n; i++) {
                if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) {
                        while (i--)
                                free(neigh[i]);
                        return;                 /* ENOMEM -- abandon effort */
                }
                neigh[i][0] = i;                /* identity is terminator */
        }
                                        /* make neighbor lists */
        for (r = 0; r < NRED; r++)
            for (g = 0; g < NGRN; g++)
                for (b = 0; b < NBLU; b++) {
                    if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b])
                        addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
                    if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b])
                        addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
                    if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1])
                        addneigh(neigh, histo[r][g][b], histo[r][g][b+1]);
                }
                                        /* assign closest values */
        for (r = 0; r < NRED; r++)
            for (g = 0; g < NGRN; g++)
                for (b = 0; b < NBLU; b++)
                    setclosest(neigh, r, g, b);
                                        /* free neighbor lists */
        for (i = 0; i < n; i++)
                free(neigh[i]);
#undef i
}


static
addneigh(nl, i, j)              /* i and j are neighbors; add them to list */
register BYTE   *nl[];
register int    i;
int     j;
{
        int     nc;
        char    *nnl;
        register int    t;
        
        for (nc = 0; nc < 2; nc++) {            /* do both neighbors */
                for (t = 0; nl[i][t] != i; t++)
                        if (nl[i][t] == j)
                                break;          /* in list already */
                if (nl[i][t] == i) {            /* add to list */
                        nl[i][t++] = j;
                        if (t % NBSIZ == 0) {   /* enlarge list */
                                if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL)
                                        t--;
                                else
                                        nl[i] = (BYTE *)nnl;
                        }
                        nl[i][t] = i;           /* terminator */
                }
                t = i; i = j; j = t;            /* swap and do it again */
        }
}


static unsigned
dist(col, r, g, b)              /* find distance from clrtab entry to r,g,b */
register BYTE   col[3];
int     r, g, b;
{
        register int    tmp;
        register unsigned       sum;
        
        tmp = col[RED]*NRED/256 - r;
        sum = tmp*tmp;
        tmp = col[GRN]*NGRN/256 - g;
        sum += tmp*tmp;
        tmp = col[BLU]*NBLU/256 - b;
        sum += tmp*tmp;
        return(sum);
}


static
setclosest(nl, r, g, b)         /* find index closest to color and assign */
BYTE    *nl[];
int     r, g, b;
{
        int     ident;
        unsigned        min;
        register unsigned       d;
        register BYTE   *p;
                                        /* get starting value */
        min = dist(clrtab[ident=histo[r][g][b]], r, g, b);
                                        /* find minimum */
        for (p = nl[ident]; *p != ident; p++)
                if ((d = dist(clrtab[*p], r, g, b)) < min) {
                        min = d;
                        histo[r][g][b] = *p;
                }
}
#endif
Revision:	2.10
Committed:	Fri Jun 10 12:51:16 1994 UTC (29 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.9:	+4 -2 lines
Log Message:	added Anthony Dekker's neural net color quantization code
#	User	Rev	Content
1	greg	2.4	/* Copyright (c) 1993 Regents of the University of California */
2	greg	2.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Simple median-cut color quantization based on colortab.c
9			*/
10
11			#include "standard.h"
12
13			#include "color.h"
14			/* histogram resolution */
15			#define NRED 36
16			#define NGRN 48
17			#define NBLU 24
18			#define HMAX NGRN
19			/* minimum box count for adaptive partition */
20			#define MINSAMP 7
21			/* color partition */
22			#define set_branch(p,c) ((c)<<2\|(p))
23			#define part(cn) ((cn)>>2)
24			#define prim(cn) ((cn)&3)
25			/* our color table (global) */
26	greg	2.10	extern BYTE clrtab[256][3];
27	greg	2.1	/* histogram of colors / color assignments */
28			static unsigned histo[NRED][NGRN][NBLU];
29			#define cndx(c) histo[((c)[RED]NRED)>>8][((c)[GRN]NGRN)>>8][((c)[BLU]*NBLU)>>8]
30			/* initial color cube boundary */
31			static int CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU};
32			/* maximum propagated error during dithering */
33			#define MAXERR 20
34	greg	2.2	/* define CLOSEST to get closest colors */
35	greg	2.4	#ifndef CLOSEST
36			#ifdef SPEED
37			#if SPEED > 8
38			#define CLOSEST 1 /* this step takes a little longer */
39			#endif
40			#endif
41			#endif
42	greg	2.1
43
44	greg	2.10	new_histo(n) /* clear our histogram */
45			int n;
46	greg	2.1	{
47			bzero((char *)histo, sizeof(histo));
48	greg	2.10	return(0);
49	greg	2.1	}
50
51
52			cnt_pixel(col) /* add pixel to our histogram */
53			register BYTE col[];
54			{
55			cndx(col)++;
56			}
57
58
59			cnt_colrs(cs, n) /* add a scanline to our histogram */
60			register COLR *cs;
61			register int n;
62			{
63			while (n-- > 0) {
64			cndx(cs[0])++;
65			cs++;
66			}
67			}
68
69
70			new_clrtab(ncolors) /* make new color table using ncolors */
71			int ncolors;
72			{
73			if (ncolors < 1)
74			return(0);
75			if (ncolors > 256)
76			ncolors = 256;
77			/* partition color space */
78			cut(CLRCUBE, 0, ncolors);
79	greg	2.2	#ifdef CLOSEST
80			closest(ncolors); /* ensure colors picked are closest */
81			#endif
82	greg	2.9	/* reset dithering function */
83			dith_colrs((BYTE )NULL, (COLR )NULL, 0);
84	greg	2.1	/* return new color table size */
85			return(ncolors);
86			}
87
88
89			int
90			map_pixel(col) /* get pixel for color */
91			register BYTE col[];
92			{
93			return(cndx(col));
94			}
95
96
97			map_colrs(bs, cs, n) /* convert a scanline to color index values */
98			register BYTE *bs;
99			register COLR *cs;
100			register int n;
101			{
102			while (n-- > 0) {
103			*bs++ = cndx(cs[0]);
104			cs++;
105			}
106			}
107
108
109			dith_colrs(bs, cs, n) /* convert scanline to dithered index values */
110			register BYTE *bs;
111			register COLR *cs;
112			int n;
113			{
114	greg	2.8	static short (*cerr)[3] = NULL;
115	greg	2.1	static int N = 0;
116			int err[3], errp[3];
117			register int x, i;
118
119			if (n != N) { /* get error propogation array */
120	greg	2.8	if (N) {
121			free((char *)cerr);
122			cerr = NULL;
123			}
124			if (n)
125	greg	2.1	cerr = (short ()[3])malloc(3n*sizeof(short));
126			if (cerr == NULL) {
127			N = 0;
128			map_colrs(bs, cs, n);
129			return;
130			}
131			N = n;
132			bzero((char )cerr, 3N*sizeof(short));
133			}
134			err[0] = err[1] = err[2] = 0;
135			for (x = 0; x < n; x++) {
136			for (i = 0; i < 3; i++) { /* dither value */
137			errp[i] = err[i];
138			err[i] += cerr[x][i];
139			#ifdef MAXERR
140			if (err[i] > MAXERR) err[i] = MAXERR;
141			else if (err[i] < -MAXERR) err[i] = -MAXERR;
142			#endif
143			err[i] += cs[x][i];
144			if (err[i] < 0) err[i] = 0;
145			else if (err[i] > 255) err[i] = 255;
146			}
147			bs[x] = cndx(err);
148			for (i = 0; i < 3; i++) { /* propagate error */
149			err[i] -= clrtab[bs[x]][i];
150			err[i] /= 3;
151			cerr[x][i] = err[i] + errp[i];
152			}
153			}
154			}
155
156
157			static
158			cut(box, c0, c1) /* partition color space */
159			register int box[3][2];
160			int c0, c1;
161			{
162			register int branch;
163			int kb[3][2];
164
165			if (c1-c0 <= 1) { /* assign pixel */
166			mktabent(c0, box);
167			return;
168			}
169			/* split box */
170			branch = split(box);
171			bcopy((char )box, (char )kb, sizeof(kb));
172			/* do left (lesser) branch */
173			kb[prim(branch)][1] = part(branch);
174			cut(kb, c0, (c0+c1)>>1);
175			/* do right branch */
176			kb[prim(branch)][0] = part(branch);
177			kb[prim(branch)][1] = box[prim(branch)][1];
178			cut(kb, (c0+c1)>>1, c1);
179			}
180
181
182			static int
183			split(box) /* find median cut for box */
184			register int box[3][2];
185			{
186			#define c0 r
187			register int r, g, b;
188			int pri;
189	greg	2.6	long t[HMAX], med;
190	greg	2.1	/* find dominant axis */
191			pri = RED;
192			if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
193			pri = GRN;
194			if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
195			pri = BLU;
196			/* sum histogram over box */
197			med = 0;
198			switch (pri) {
199			case RED:
200			for (r = box[RED][0]; r < box[RED][1]; r++) {
201			t[r] = 0;
202			for (g = box[GRN][0]; g < box[GRN][1]; g++)
203			for (b = box[BLU][0]; b < box[BLU][1]; b++)
204			t[r] += histo[r][g][b];
205			med += t[r];
206			}
207			break;
208			case GRN:
209			for (g = box[GRN][0]; g < box[GRN][1]; g++) {
210			t[g] = 0;
211			for (b = box[BLU][0]; b < box[BLU][1]; b++)
212			for (r = box[RED][0]; r < box[RED][1]; r++)
213			t[g] += histo[r][g][b];
214			med += t[g];
215			}
216			break;
217			case BLU:
218			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
219			t[b] = 0;
220			for (r = box[RED][0]; r < box[RED][1]; r++)
221			for (g = box[GRN][0]; g < box[GRN][1]; g++)
222			t[b] += histo[r][g][b];
223			med += t[b];
224			}
225			break;
226			}
227			if (med < MINSAMP) /* if too sparse, split at midpoint */
228			return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
229			/* find median position */
230			med >>= 1;
231			for (c0 = box[pri][0]; med > 0; c0++)
232			med -= t[c0];
233			if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */
234			c0--; /* part left of median */
235			return(set_branch(pri,c0));
236			#undef c0
237			}
238
239
240			static
241			mktabent(p, box) /* compute average color for box and assign */
242			int p;
243			register int box[3][2];
244			{
245	greg	2.5	unsigned long sum[3];
246	greg	2.7	unsigned r, g;
247			unsigned long n;
248	greg	2.5	register unsigned b, c;
249	greg	2.1	/* sum pixels in box */
250			n = 0;
251			sum[RED] = sum[GRN] = sum[BLU] = 0;
252			for (r = box[RED][0]; r < box[RED][1]; r++)
253			for (g = box[GRN][0]; g < box[GRN][1]; g++)
254			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
255			if (c = histo[r][g][b]) {
256			n += c;
257			sum[RED] += (long)c*r;
258			sum[GRN] += (long)c*g;
259			sum[BLU] += (long)c*b;
260			}
261			histo[r][g][b] = p; /* assign pixel */
262			}
263	greg	2.7	if (n >= (1L<<23)/HMAX) { /* avoid overflow */
264	greg	2.5	sum[RED] /= n;
265			sum[GRN] /= n;
266			sum[BLU] /= n;
267			n = 1;
268			}
269	greg	2.1	if (n) { /* compute average */
270			clrtab[p][RED] = sum[RED]*256/NRED/n;
271			clrtab[p][GRN] = sum[GRN]*256/NGRN/n;
272			clrtab[p][BLU] = sum[BLU]*256/NBLU/n;
273			} else { /* empty box -- use midpoint */
274			clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2;
275			clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2;
276			clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2;
277			}
278			}
279	greg	2.2
280
281			#ifdef CLOSEST
282			#define NBSIZ 32
283			static
284			closest(n) /* make sure we have the closest colors */
285			int n;
286			{
287			BYTE *neigh[256];
288			register int r, g, b;
289			#define i r
290			/* get space for neighbor lists */
291			for (i = 0; i < n; i++) {
292			if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) {
293			while (i--)
294			free(neigh[i]);
295			return; /* ENOMEM -- abandon effort */
296			}
297			neigh[i][0] = i; /* identity is terminator */
298			}
299			/* make neighbor lists */
300	greg	2.3	for (r = 0; r < NRED; r++)
301			for (g = 0; g < NGRN; g++)
302			for (b = 0; b < NBLU; b++) {
303			if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b])
304	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
305	greg	2.3	if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b])
306	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
307	greg	2.3	if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1])
308	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r][g][b+1]);
309			}
310			/* assign closest values */
311			for (r = 0; r < NRED; r++)
312			for (g = 0; g < NGRN; g++)
313			for (b = 0; b < NBLU; b++)
314			setclosest(neigh, r, g, b);
315			/* free neighbor lists */
316			for (i = 0; i < n; i++)
317			free(neigh[i]);
318			#undef i
319			}
320
321
322			static
323			addneigh(nl, i, j) /* i and j are neighbors; add them to list */
324			register BYTE *nl[];
325			register int i;
326			int j;
327			{
328			int nc;
329			char *nnl;
330			register int t;
331
332			for (nc = 0; nc < 2; nc++) { /* do both neighbors */
333			for (t = 0; nl[i][t] != i; t++)
334			if (nl[i][t] == j)
335			break; /* in list already */
336			if (nl[i][t] == i) { /* add to list */
337			nl[i][t++] = j;
338			if (t % NBSIZ == 0) { /* enlarge list */
339			if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL)
340			t--;
341			else
342			nl[i] = (BYTE *)nnl;
343			}
344			nl[i][t] = i; /* terminator */
345			}
346			t = i; i = j; j = t; /* swap and do it again */
347			}
348			}
349
350
351			static unsigned
352			dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */
353			register BYTE col[3];
354			int r, g, b;
355			{
356	greg	2.4	register int tmp;
357	greg	2.2	register unsigned sum;
358
359			tmp = col[RED]*NRED/256 - r;
360			sum = tmp*tmp;
361			tmp = col[GRN]*NGRN/256 - g;
362			sum += tmp*tmp;
363			tmp = col[BLU]*NBLU/256 - b;
364			sum += tmp*tmp;
365			return(sum);
366			}
367
368
369			static
370			setclosest(nl, r, g, b) /* find index closest to color and assign */
371			BYTE *nl[];
372			int r, g, b;
373			{
374			int ident;
375			unsigned min;
376			register unsigned d;
377			register BYTE *p;
378			/* get starting value */
379			min = dist(clrtab[ident=histo[r][g][b]], r, g, b);
380			/* find minimum */
381			for (p = nl[ident]; *p != ident; p++)
382			if ((d = dist(clrtab[*p], r, g, b)) < min) {
383			min = d;
384			histo[r][g][b] = *p;
385			}
386			}
387			#endif