src/px/clrtab.c

/* Copyright (c) 1992 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) */
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 */
#define CLOSEST         1


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


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
                                /* 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];
        static int      N = 0;
        int     err[3], errp[3];
        register int    x, i;

        if (n != N) {           /* get error propogation array */
                if (N)
                        cerr = (short (*)[3])realloc((char *)cerr,
                                        3*n*sizeof(short));
                else
                        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;
        int     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];
{
        long    sum[3];
        int     r, g, n;
        register int    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) {                                /* 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-1; r++)
            for (g = 0; g < NGRN-1; g++)
                for (b = 0; b < NBLU-1; b++) {
                    if (histo[r][g][b] != histo[r+1][g][b])
                        addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
                    if (histo[r][g][b] != histo[r][g+1][b])
                        addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
                    if (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 unsigned       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:	2.2
Committed:	Tue Oct 13 09:07:51 1992 UTC (31 years, 6 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+114 -0 lines
Log Message:	added closest color calculation
#	User	Rev	Content
1	greg	2.1	/* Copyright (c) 1992 Regents of the University of California */
2
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			BYTE clrtab[256][3];
27			/* 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			#define CLOSEST 1
36	greg	2.1
37
38			new_histo() /* clear our histogram */
39			{
40			bzero((char *)histo, sizeof(histo));
41			}
42
43
44			cnt_pixel(col) /* add pixel to our histogram */
45			register BYTE col[];
46			{
47			cndx(col)++;
48			}
49
50
51			cnt_colrs(cs, n) /* add a scanline to our histogram */
52			register COLR *cs;
53			register int n;
54			{
55			while (n-- > 0) {
56			cndx(cs[0])++;
57			cs++;
58			}
59			}
60
61
62			new_clrtab(ncolors) /* make new color table using ncolors */
63			int ncolors;
64			{
65			if (ncolors < 1)
66			return(0);
67			if (ncolors > 256)
68			ncolors = 256;
69			/* partition color space */
70			cut(CLRCUBE, 0, ncolors);
71	greg	2.2	#ifdef CLOSEST
72			closest(ncolors); /* ensure colors picked are closest */
73			#endif
74	greg	2.1	/* return new color table size */
75			return(ncolors);
76			}
77
78
79			int
80			map_pixel(col) /* get pixel for color */
81			register BYTE col[];
82			{
83			return(cndx(col));
84			}
85
86
87			map_colrs(bs, cs, n) /* convert a scanline to color index values */
88			register BYTE *bs;
89			register COLR *cs;
90			register int n;
91			{
92			while (n-- > 0) {
93			*bs++ = cndx(cs[0]);
94			cs++;
95			}
96			}
97
98
99			dith_colrs(bs, cs, n) /* convert scanline to dithered index values */
100			register BYTE *bs;
101			register COLR *cs;
102			int n;
103			{
104			static short (*cerr)[3];
105			static int N = 0;
106			int err[3], errp[3];
107			register int x, i;
108
109			if (n != N) { /* get error propogation array */
110			if (N)
111			cerr = (short ()[3])realloc((char )cerr,
112			3nsizeof(short));
113			else
114			cerr = (short ()[3])malloc(3n*sizeof(short));
115			if (cerr == NULL) {
116			N = 0;
117			map_colrs(bs, cs, n);
118			return;
119			}
120			N = n;
121			bzero((char )cerr, 3N*sizeof(short));
122			}
123			err[0] = err[1] = err[2] = 0;
124			for (x = 0; x < n; x++) {
125			for (i = 0; i < 3; i++) { /* dither value */
126			errp[i] = err[i];
127			err[i] += cerr[x][i];
128			#ifdef MAXERR
129			if (err[i] > MAXERR) err[i] = MAXERR;
130			else if (err[i] < -MAXERR) err[i] = -MAXERR;
131			#endif
132			err[i] += cs[x][i];
133			if (err[i] < 0) err[i] = 0;
134			else if (err[i] > 255) err[i] = 255;
135			}
136			bs[x] = cndx(err);
137			for (i = 0; i < 3; i++) { /* propagate error */
138			err[i] -= clrtab[bs[x]][i];
139			err[i] /= 3;
140			cerr[x][i] = err[i] + errp[i];
141			}
142			}
143			}
144
145
146			static
147			cut(box, c0, c1) /* partition color space */
148			register int box[3][2];
149			int c0, c1;
150			{
151			register int branch;
152			int kb[3][2];
153
154			if (c1-c0 <= 1) { /* assign pixel */
155			mktabent(c0, box);
156			return;
157			}
158			/* split box */
159			branch = split(box);
160			bcopy((char )box, (char )kb, sizeof(kb));
161			/* do left (lesser) branch */
162			kb[prim(branch)][1] = part(branch);
163			cut(kb, c0, (c0+c1)>>1);
164			/* do right branch */
165			kb[prim(branch)][0] = part(branch);
166			kb[prim(branch)][1] = box[prim(branch)][1];
167			cut(kb, (c0+c1)>>1, c1);
168			}
169
170
171			static int
172			split(box) /* find median cut for box */
173			register int box[3][2];
174			{
175			#define c0 r
176			register int r, g, b;
177			int pri;
178			int t[HMAX], med;
179			/* find dominant axis */
180			pri = RED;
181			if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
182			pri = GRN;
183			if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
184			pri = BLU;
185			/* sum histogram over box */
186			med = 0;
187			switch (pri) {
188			case RED:
189			for (r = box[RED][0]; r < box[RED][1]; r++) {
190			t[r] = 0;
191			for (g = box[GRN][0]; g < box[GRN][1]; g++)
192			for (b = box[BLU][0]; b < box[BLU][1]; b++)
193			t[r] += histo[r][g][b];
194			med += t[r];
195			}
196			break;
197			case GRN:
198			for (g = box[GRN][0]; g < box[GRN][1]; g++) {
199			t[g] = 0;
200			for (b = box[BLU][0]; b < box[BLU][1]; b++)
201			for (r = box[RED][0]; r < box[RED][1]; r++)
202			t[g] += histo[r][g][b];
203			med += t[g];
204			}
205			break;
206			case BLU:
207			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
208			t[b] = 0;
209			for (r = box[RED][0]; r < box[RED][1]; r++)
210			for (g = box[GRN][0]; g < box[GRN][1]; g++)
211			t[b] += histo[r][g][b];
212			med += t[b];
213			}
214			break;
215			}
216			if (med < MINSAMP) /* if too sparse, split at midpoint */
217			return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
218			/* find median position */
219			med >>= 1;
220			for (c0 = box[pri][0]; med > 0; c0++)
221			med -= t[c0];
222			if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */
223			c0--; /* part left of median */
224			return(set_branch(pri,c0));
225			#undef c0
226			}
227
228
229			static
230			mktabent(p, box) /* compute average color for box and assign */
231			int p;
232			register int box[3][2];
233			{
234			long sum[3];
235			int r, g, n;
236			register int b, c;
237			/* sum pixels in box */
238			n = 0;
239			sum[RED] = sum[GRN] = sum[BLU] = 0;
240			for (r = box[RED][0]; r < box[RED][1]; r++)
241			for (g = box[GRN][0]; g < box[GRN][1]; g++)
242			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
243			if (c = histo[r][g][b]) {
244			n += c;
245			sum[RED] += (long)c*r;
246			sum[GRN] += (long)c*g;
247			sum[BLU] += (long)c*b;
248			}
249			histo[r][g][b] = p; /* assign pixel */
250			}
251			if (n) { /* compute average */
252			clrtab[p][RED] = sum[RED]*256/NRED/n;
253			clrtab[p][GRN] = sum[GRN]*256/NGRN/n;
254			clrtab[p][BLU] = sum[BLU]*256/NBLU/n;
255			} else { /* empty box -- use midpoint */
256			clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2;
257			clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2;
258			clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2;
259			}
260			}
261	greg	2.2
262
263			#ifdef CLOSEST
264			#define NBSIZ 32
265			static
266			closest(n) /* make sure we have the closest colors */
267			int n;
268			{
269			BYTE *neigh[256];
270			register int r, g, b;
271			#define i r
272			/* get space for neighbor lists */
273			for (i = 0; i < n; i++) {
274			if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) {
275			while (i--)
276			free(neigh[i]);
277			return; /* ENOMEM -- abandon effort */
278			}
279			neigh[i][0] = i; /* identity is terminator */
280			}
281			/* make neighbor lists */
282			for (r = 0; r < NRED-1; r++)
283			for (g = 0; g < NGRN-1; g++)
284			for (b = 0; b < NBLU-1; b++) {
285			if (histo[r][g][b] != histo[r+1][g][b])
286			addneigh(neigh, histo[r][g][b], histo[r+1][g][b]);
287			if (histo[r][g][b] != histo[r][g+1][b])
288			addneigh(neigh, histo[r][g][b], histo[r][g+1][b]);
289			if (histo[r][g][b] != histo[r][g][b+1])
290			addneigh(neigh, histo[r][g][b], histo[r][g][b+1]);
291			}
292			/* assign closest values */
293			for (r = 0; r < NRED; r++)
294			for (g = 0; g < NGRN; g++)
295			for (b = 0; b < NBLU; b++)
296			setclosest(neigh, r, g, b);
297			/* free neighbor lists */
298			for (i = 0; i < n; i++)
299			free(neigh[i]);
300			#undef i
301			}
302
303
304			static
305			addneigh(nl, i, j) /* i and j are neighbors; add them to list */
306			register BYTE *nl[];
307			register int i;
308			int j;
309			{
310			int nc;
311			char *nnl;
312			register int t;
313
314			for (nc = 0; nc < 2; nc++) { /* do both neighbors */
315			for (t = 0; nl[i][t] != i; t++)
316			if (nl[i][t] == j)
317			break; /* in list already */
318			if (nl[i][t] == i) { /* add to list */
319			nl[i][t++] = j;
320			if (t % NBSIZ == 0) { /* enlarge list */
321			if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL)
322			t--;
323			else
324			nl[i] = (BYTE *)nnl;
325			}
326			nl[i][t] = i; /* terminator */
327			}
328			t = i; i = j; j = t; /* swap and do it again */
329			}
330			}
331
332
333			static unsigned
334			dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */
335			register BYTE col[3];
336			int r, g, b;
337			{
338			register unsigned tmp;
339			register unsigned sum;
340
341			tmp = col[RED]*NRED/256 - r;
342			sum = tmp*tmp;
343			tmp = col[GRN]*NGRN/256 - g;
344			sum += tmp*tmp;
345			tmp = col[BLU]*NBLU/256 - b;
346			sum += tmp*tmp;
347			return(sum);
348			}
349
350
351			static
352			setclosest(nl, r, g, b) /* find index closest to color and assign */
353			BYTE *nl[];
354			int r, g, b;
355			{
356			int ident;
357			unsigned min;
358			register unsigned d;
359			register BYTE *p;
360			/* get starting value */
361			min = dist(clrtab[ident=histo[r][g][b]], r, g, b);
362			/* find minimum */
363			for (p = nl[ident]; *p != ident; p++)
364			if ((d = dist(clrtab[*p], r, g, b)) < min) {
365			min = d;
366			histo[r][g][b] = *p;
367			}
368			}
369			#endif