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

static  cut(), mktabent(), closest(), addneigh(), setclosest();
static int      split();
static unsigned dist();


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:	2.11
Committed:	Mon Dec 12 12:15:51 1994 UTC (29 years, 4 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.10:	+4 -0 lines
Log Message:	added static function definitions
#	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	greg	2.11	static cut(), mktabent(), closest(), addneigh(), setclosest();
44			static int split();
45			static unsigned dist();
46
47	greg	2.1
48	greg	2.10	new_histo(n) /* clear our histogram */
49			int n;
50	greg	2.1	{
51			bzero((char *)histo, sizeof(histo));
52	greg	2.10	return(0);
53	greg	2.1	}
54
55
56			cnt_pixel(col) /* add pixel to our histogram */
57			register BYTE col[];
58			{
59			cndx(col)++;
60			}
61
62
63			cnt_colrs(cs, n) /* add a scanline to our histogram */
64			register COLR *cs;
65			register int n;
66			{
67			while (n-- > 0) {
68			cndx(cs[0])++;
69			cs++;
70			}
71			}
72
73
74			new_clrtab(ncolors) /* make new color table using ncolors */
75			int ncolors;
76			{
77			if (ncolors < 1)
78			return(0);
79			if (ncolors > 256)
80			ncolors = 256;
81			/* partition color space */
82			cut(CLRCUBE, 0, ncolors);
83	greg	2.2	#ifdef CLOSEST
84			closest(ncolors); /* ensure colors picked are closest */
85			#endif
86	greg	2.9	/* reset dithering function */
87			dith_colrs((BYTE )NULL, (COLR )NULL, 0);
88	greg	2.1	/* return new color table size */
89			return(ncolors);
90			}
91
92
93			int
94			map_pixel(col) /* get pixel for color */
95			register BYTE col[];
96			{
97			return(cndx(col));
98			}
99
100
101			map_colrs(bs, cs, n) /* convert a scanline to color index values */
102			register BYTE *bs;
103			register COLR *cs;
104			register int n;
105			{
106			while (n-- > 0) {
107			*bs++ = cndx(cs[0]);
108			cs++;
109			}
110			}
111
112
113			dith_colrs(bs, cs, n) /* convert scanline to dithered index values */
114			register BYTE *bs;
115			register COLR *cs;
116			int n;
117			{
118	greg	2.8	static short (*cerr)[3] = NULL;
119	greg	2.1	static int N = 0;
120			int err[3], errp[3];
121			register int x, i;
122
123			if (n != N) { /* get error propogation array */
124	greg	2.8	if (N) {
125			free((char *)cerr);
126			cerr = NULL;
127			}
128			if (n)
129	greg	2.1	cerr = (short ()[3])malloc(3n*sizeof(short));
130			if (cerr == NULL) {
131			N = 0;
132			map_colrs(bs, cs, n);
133			return;
134			}
135			N = n;
136			bzero((char )cerr, 3N*sizeof(short));
137			}
138			err[0] = err[1] = err[2] = 0;
139			for (x = 0; x < n; x++) {
140			for (i = 0; i < 3; i++) { /* dither value */
141			errp[i] = err[i];
142			err[i] += cerr[x][i];
143			#ifdef MAXERR
144			if (err[i] > MAXERR) err[i] = MAXERR;
145			else if (err[i] < -MAXERR) err[i] = -MAXERR;
146			#endif
147			err[i] += cs[x][i];
148			if (err[i] < 0) err[i] = 0;
149			else if (err[i] > 255) err[i] = 255;
150			}
151			bs[x] = cndx(err);
152			for (i = 0; i < 3; i++) { /* propagate error */
153			err[i] -= clrtab[bs[x]][i];
154			err[i] /= 3;
155			cerr[x][i] = err[i] + errp[i];
156			}
157			}
158			}
159
160
161			static
162			cut(box, c0, c1) /* partition color space */
163			register int box[3][2];
164			int c0, c1;
165			{
166			register int branch;
167			int kb[3][2];
168
169			if (c1-c0 <= 1) { /* assign pixel */
170			mktabent(c0, box);
171			return;
172			}
173			/* split box */
174			branch = split(box);
175			bcopy((char )box, (char )kb, sizeof(kb));
176			/* do left (lesser) branch */
177			kb[prim(branch)][1] = part(branch);
178			cut(kb, c0, (c0+c1)>>1);
179			/* do right branch */
180			kb[prim(branch)][0] = part(branch);
181			kb[prim(branch)][1] = box[prim(branch)][1];
182			cut(kb, (c0+c1)>>1, c1);
183			}
184
185
186			static int
187			split(box) /* find median cut for box */
188			register int box[3][2];
189			{
190			#define c0 r
191			register int r, g, b;
192			int pri;
193	greg	2.6	long t[HMAX], med;
194	greg	2.1	/* find dominant axis */
195			pri = RED;
196			if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
197			pri = GRN;
198			if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
199			pri = BLU;
200			/* sum histogram over box */
201			med = 0;
202			switch (pri) {
203			case RED:
204			for (r = box[RED][0]; r < box[RED][1]; r++) {
205			t[r] = 0;
206			for (g = box[GRN][0]; g < box[GRN][1]; g++)
207			for (b = box[BLU][0]; b < box[BLU][1]; b++)
208			t[r] += histo[r][g][b];
209			med += t[r];
210			}
211			break;
212			case GRN:
213			for (g = box[GRN][0]; g < box[GRN][1]; g++) {
214			t[g] = 0;
215			for (b = box[BLU][0]; b < box[BLU][1]; b++)
216			for (r = box[RED][0]; r < box[RED][1]; r++)
217			t[g] += histo[r][g][b];
218			med += t[g];
219			}
220			break;
221			case BLU:
222			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
223			t[b] = 0;
224			for (r = box[RED][0]; r < box[RED][1]; r++)
225			for (g = box[GRN][0]; g < box[GRN][1]; g++)
226			t[b] += histo[r][g][b];
227			med += t[b];
228			}
229			break;
230			}
231			if (med < MINSAMP) /* if too sparse, split at midpoint */
232			return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
233			/* find median position */
234			med >>= 1;
235			for (c0 = box[pri][0]; med > 0; c0++)
236			med -= t[c0];
237			if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */
238			c0--; /* part left of median */
239			return(set_branch(pri,c0));
240			#undef c0
241			}
242
243
244			static
245			mktabent(p, box) /* compute average color for box and assign */
246			int p;
247			register int box[3][2];
248			{
249	greg	2.5	unsigned long sum[3];
250	greg	2.7	unsigned r, g;
251			unsigned long n;
252	greg	2.5	register unsigned b, c;
253	greg	2.1	/* sum pixels in box */
254			n = 0;
255			sum[RED] = sum[GRN] = sum[BLU] = 0;
256			for (r = box[RED][0]; r < box[RED][1]; r++)
257			for (g = box[GRN][0]; g < box[GRN][1]; g++)
258			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
259			if (c = histo[r][g][b]) {
260			n += c;
261			sum[RED] += (long)c*r;
262			sum[GRN] += (long)c*g;
263			sum[BLU] += (long)c*b;
264			}
265			histo[r][g][b] = p; /* assign pixel */
266			}
267	greg	2.7	if (n >= (1L<<23)/HMAX) { /* avoid overflow */
268	greg	2.5	sum[RED] /= n;
269			sum[GRN] /= n;
270			sum[BLU] /= n;
271			n = 1;
272			}
273	greg	2.1	if (n) { /* compute average */
274			clrtab[p][RED] = sum[RED]*256/NRED/n;
275			clrtab[p][GRN] = sum[GRN]*256/NGRN/n;
276			clrtab[p][BLU] = sum[BLU]*256/NBLU/n;
277			} else { /* empty box -- use midpoint */
278			clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2;
279			clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2;
280			clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2;
281			}
282			}
283	greg	2.2
284
285			#ifdef CLOSEST
286			#define NBSIZ 32
287			static
288			closest(n) /* make sure we have the closest colors */
289			int n;
290			{
291			BYTE *neigh[256];
292			register int r, g, b;
293			#define i r
294			/* get space for neighbor lists */
295			for (i = 0; i < n; i++) {
296			if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) {
297			while (i--)
298			free(neigh[i]);
299			return; /* ENOMEM -- abandon effort */
300			}
301			neigh[i][0] = i; /* identity is terminator */
302			}
303			/* make neighbor lists */
304	greg	2.3	for (r = 0; r < NRED; r++)
305			for (g = 0; g < NGRN; g++)
306			for (b = 0; b < NBLU; b++) {
307			if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b])
308	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
309	greg	2.3	if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b])
310	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
311	greg	2.3	if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1])
312	greg	2.2	addneigh(neigh, histo[r][g][b], histo[r][g][b+1]);
313			}
314			/* assign closest values */
315			for (r = 0; r < NRED; r++)
316			for (g = 0; g < NGRN; g++)
317			for (b = 0; b < NBLU; b++)
318			setclosest(neigh, r, g, b);
319			/* free neighbor lists */
320			for (i = 0; i < n; i++)
321			free(neigh[i]);
322			#undef i
323			}
324
325
326			static
327			addneigh(nl, i, j) /* i and j are neighbors; add them to list */
328			register BYTE *nl[];
329			register int i;
330			int j;
331			{
332			int nc;
333			char *nnl;
334			register int t;
335
336			for (nc = 0; nc < 2; nc++) { /* do both neighbors */
337			for (t = 0; nl[i][t] != i; t++)
338			if (nl[i][t] == j)
339			break; /* in list already */
340			if (nl[i][t] == i) { /* add to list */
341			nl[i][t++] = j;
342			if (t % NBSIZ == 0) { /* enlarge list */
343			if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL)
344			t--;
345			else
346			nl[i] = (BYTE *)nnl;
347			}
348			nl[i][t] = i; /* terminator */
349			}
350			t = i; i = j; j = t; /* swap and do it again */
351			}
352			}
353
354
355			static unsigned
356			dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */
357			register BYTE col[3];
358			int r, g, b;
359			{
360	greg	2.4	register int tmp;
361	greg	2.2	register unsigned sum;
362
363			tmp = col[RED]*NRED/256 - r;
364			sum = tmp*tmp;
365			tmp = col[GRN]*NGRN/256 - g;
366			sum += tmp*tmp;
367			tmp = col[BLU]*NBLU/256 - b;
368			sum += tmp*tmp;
369			return(sum);
370			}
371
372
373			static
374			setclosest(nl, r, g, b) /* find index closest to color and assign */
375			BYTE *nl[];
376			int r, g, b;
377			{
378			int ident;
379			unsigned min;
380			register unsigned d;
381			register BYTE *p;
382			/* get starting value */
383			min = dist(clrtab[ident=histo[r][g][b]], r, g, b);
384			/* find minimum */
385			for (p = nl[ident]; *p != ident; p++)
386			if ((d = dist(clrtab[*p], r, g, b)) < min) {
387			min = d;
388			histo[r][g][b] = *p;
389			}
390			}
391			#endif