src/rt/colortab.c

/* Copyright (c) 1989 Regents of the University of California */

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

/*
 * colortab.c - allocate and control dynamic color table.
 *
 *      We start off with a uniform partition of color space.
 *      As pixels are sent to the frame buffer, a histogram is built.
 *      When a new color table is requested, the histogram is used
 *      to make a pseudo-optimal partition, after which the
 *      histogram is cleared.  This algorithm
 *      performs only as well as the next drawing's color
 *      distribution is correlated to the last.
 */

#include "standard.h"

#include "color.h"
                                /* histogram resolution */
#define NRED            24
#define NGRN            32
#define NBLU            16
#define HMAX            NGRN
                                /* minimum box count for adaptive partition */
#define MINSAMP         7
                                /* maximum distance^2 before color reassign */
#define MAXDST2         12
                                /* map a color */
#define map_col(c,p)    clrmap[p][ colval(c,p)<1. ? \
                                (int)(colval(c,p)*256.) : 255 ]
                                /* color partition tree */
#define CNODE           short
#define set_branch(p,c) ((c)<<2|(p))
#define set_pval(pv)    ((pv)<<2|3)
#define is_branch(cn)   (((cn)&3)!=3)
#define is_pval(cn)     (((cn)&3)==3)
#define part(cn)        ((cn)>>2)
#define prim(cn)        ((cn)&3)
#define pval(cn)        ((cn)>>2)
                                /* our color table */
static struct tabent {
        long    sum[3];         /* sum of colors using this entry */
        int     n;              /* number of colors */
        BYTE    ent[3];         /* current table value */
}       *clrtab = NULL;
                                /* color cube partition */
static CNODE    *ctree = NULL;
                                /* our color correction map */
static BYTE     clrmap[3][256];
                                /* histogram of colors used */
static unsigned short   histo[NRED][NGRN][NBLU];
                                /* initial color cube boundary */
static int      CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU};


int
new_ctab(ncolors)               /* start new color table with max ncolors */
int     ncolors;
{
        int     treesize;

        if (ncolors < 1)
                return(0);
                                /* free old tables */
        if (clrtab != NULL)
                free((char *)clrtab);
        if (ctree != NULL)
                free((char *)ctree);
                                /* get new tables */
        for (treesize = 1; treesize < ncolors; treesize <<= 1)
                ;
        treesize <<= 1;
        clrtab = (struct tabent *)calloc(ncolors, sizeof(struct tabent));
        ctree = (CNODE *)malloc(treesize*sizeof(CNODE));
        if (clrtab == NULL || ctree == NULL)
                return(0);
                                /* partition color space */
        cut(ctree, 0, CLRCUBE, 0, ncolors);
                                /* clear histogram */
        bzero((char *)histo, sizeof(histo));
                                /* return number of colors used */
        return(ncolors);
}


int
get_pixel(col, set_pixel)       /* get pixel for color */
COLOR   col;
int     (*set_pixel)();
{
        extern char     errmsg[];
        int     r, g, b;
        int     cv[3];
        register CNODE  *tp;
        register int    h;
                                                /* map color */
        r = map_col(col,RED);
        g = map_col(col,GRN);
        b = map_col(col,BLU);
                                                /* reduce resolution */
        cv[RED] = (r*NRED)>>8;
        cv[GRN] = (g*NGRN)>>8;
        cv[BLU] = (b*NBLU)>>8;
                                                /* add to histogram */
        histo[cv[RED]][cv[GRN]][cv[BLU]]++;
                                                /* find pixel in tree */
        for (tp = ctree, h = 0; is_branch(*tp); h++)
                if (cv[prim(*tp)] < part(*tp))
                        tp += 1<<h;             /* left branch */
                else
                        tp += 1<<(h+1);         /* right branch */
        h = pval(*tp);
                                                /* add to color table */
        clrtab[h].sum[RED] += r;
        clrtab[h].sum[GRN] += g;
        clrtab[h].sum[BLU] += b;
        clrtab[h].n++;
                                        /* recompute average */
        r = clrtab[h].sum[RED] / clrtab[h].n;
        g = clrtab[h].sum[GRN] / clrtab[h].n;
        b = clrtab[h].sum[BLU] / clrtab[h].n;
                                        /* check for movement */
        if (clrtab[h].n == 1 ||
                        (r-clrtab[h].ent[RED])*(r-clrtab[h].ent[RED]) +
                        (g-clrtab[h].ent[GRN])*(g-clrtab[h].ent[GRN]) +
                        (b-clrtab[h].ent[BLU])*(b-clrtab[h].ent[BLU]) > MAXDST2) {
                clrtab[h].ent[RED] = r;
                clrtab[h].ent[GRN] = g; /* reassign pixel */
                clrtab[h].ent[BLU] = b;
#ifdef DEBUG
                sprintf(errmsg, "pixel %d = (%d,%d,%d) (%d refs)\n",
                                h, r, g, b, clrtab[h].n);
                eputs(errmsg);
#endif
                (*set_pixel)(h, r, g, b);
        }
        return(h);                              /* return pixel value */
}


make_gmap(gam)                  /* make gamma correction map */
double  gam;
{
        extern double   pow();
        register int    i;
        
        for (i = 0; i < 256; i++)
                clrmap[RED][i] =
                clrmap[GRN][i] =
                clrmap[BLU][i] = 256.0 * pow((i+0.5)/256.0, 1.0/gam);
}


set_cmap(rmap, gmap, bmap)      /* set custom color correction map */
BYTE    *rmap, *gmap, *bmap;
{
        bcopy((char *)rmap, (char *)clrmap[RED], 256);
        bcopy((char *)gmap, (char *)clrmap[GRN], 256);
        bcopy((char *)bmap, (char *)clrmap[BLU], 256);
}


map_color(rgb, col)             /* map a color to a byte triplet */
BYTE    rgb[3];
COLOR   col;
{
        rgb[RED] = map_col(col,RED);
        rgb[GRN] = map_col(col,GRN);
        rgb[BLU] = map_col(col,BLU);
}


static
cut(tree, level, box, c0, c1)           /* partition color space */
register CNODE  *tree;
int     level;
register int    box[3][2];
int     c0, c1;
{
        int     kb[3][2];
        
        if (c1-c0 <= 1) {               /* assign pixel */
                *tree = set_pval(c0);
                return;
        }
                                        /* split box */
        *tree = split(box);
        bcopy((char *)box, (char *)kb, sizeof(kb));
                                                /* do left (lesser) branch */
        kb[prim(*tree)][1] = part(*tree);
        cut(tree+(1<<level), level+1, kb, c0, (c0+c1)>>1);
                                                /* do right branch */
        kb[prim(*tree)][0] = part(*tree);
        kb[prim(*tree)][1] = box[prim(*tree)][1];
        cut(tree+(1<<(level+1)), level+1, 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
}
Revision:	1.15
Committed:	Wed Nov 7 17:16:58 1990 UTC (33 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.14:	+6 -6 lines
Log Message:	minor fixes to gamma correction
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1989 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* colortab.c - allocate and control dynamic color table.
9			*
10			* We start off with a uniform partition of color space.
11			* As pixels are sent to the frame buffer, a histogram is built.
12			* When a new color table is requested, the histogram is used
13			* to make a pseudo-optimal partition, after which the
14			* histogram is cleared. This algorithm
15			* performs only as well as the next drawing's color
16			* distribution is correlated to the last.
17			*/
18
19	greg	1.15	#include "standard.h"
20
21	greg	1.1	#include "color.h"
22			/* histogram resolution */
23	greg	1.3	#define NRED 24
24	greg	1.1	#define NGRN 32
25	greg	1.3	#define NBLU 16
26	greg	1.1	#define HMAX NGRN
27			/* minimum box count for adaptive partition */
28			#define MINSAMP 7
29	greg	1.3	/* maximum distance^2 before color reassign */
30	greg	1.5	#define MAXDST2 12
31	greg	1.1	/* map a color */
32	greg	1.4	#define map_col(c,p) clrmap[p][ colval(c,p)<1. ? \
33			(int)(colval(c,p)*256.) : 255 ]
34	greg	1.1	/* color partition tree */
35			#define CNODE short
36			#define set_branch(p,c) ((c)<<2\|(p))
37			#define set_pval(pv) ((pv)<<2\|3)
38	greg	1.7	#define is_branch(cn) (((cn)&3)!=3)
39	greg	1.1	#define is_pval(cn) (((cn)&3)==3)
40			#define part(cn) ((cn)>>2)
41			#define prim(cn) ((cn)&3)
42			#define pval(cn) ((cn)>>2)
43			/* our color table */
44	greg	1.6	static struct tabent {
45	greg	1.3	long sum[3]; /* sum of colors using this entry */
46	greg	1.15	int n; /* number of colors */
47			BYTE ent[3]; /* current table value */
48	greg	1.8	} *clrtab = NULL;
49			/* color cube partition */
50			static CNODE *ctree = NULL;
51	greg	1.1	/* our color correction map */
52	greg	1.4	static BYTE clrmap[3][256];
53	greg	1.1	/* histogram of colors used */
54	greg	1.9	static unsigned short histo[NRED][NGRN][NBLU];
55	greg	1.8	/* initial color cube boundary */
56	greg	1.1	static int CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU};
57
58
59	greg	1.3	int
60	greg	1.4	new_ctab(ncolors) /* start new color table with max ncolors */
61	greg	1.1	int ncolors;
62			{
63	greg	1.8	int treesize;
64
65	greg	1.6	if (ncolors < 1)
66	greg	1.3	return(0);
67	greg	1.8	/* free old tables */
68			if (clrtab != NULL)
69			free((char *)clrtab);
70			if (ctree != NULL)
71			free((char *)ctree);
72			/* get new tables */
73			for (treesize = 1; treesize < ncolors; treesize <<= 1)
74			;
75			treesize <<= 1;
76			clrtab = (struct tabent *)calloc(ncolors, sizeof(struct tabent));
77			ctree = (CNODE )malloc(treesizesizeof(CNODE));
78			if (clrtab == NULL \|\| ctree == NULL)
79			return(0);
80	greg	1.3	/* partition color space */
81	greg	1.7	cut(ctree, 0, CLRCUBE, 0, ncolors);
82	greg	1.1	/* clear histogram */
83	greg	1.11	bzero((char *)histo, sizeof(histo));
84	greg	1.3	/* return number of colors used */
85			return(ncolors);
86	greg	1.1	}
87
88
89			int
90	greg	1.4	get_pixel(col, set_pixel) /* get pixel for color */
91	greg	1.1	COLOR col;
92	greg	1.4	int (*set_pixel)();
93	greg	1.1	{
94	greg	1.14	extern char errmsg[];
95	greg	1.3	int r, g, b;
96	greg	1.1	int cv[3];
97	greg	1.10	register CNODE *tp;
98	greg	1.1	register int h;
99	greg	1.3	/* map color */
100			r = map_col(col,RED);
101			g = map_col(col,GRN);
102			b = map_col(col,BLU);
103			/* reduce resolution */
104			cv[RED] = (r*NRED)>>8;
105			cv[GRN] = (g*NGRN)>>8;
106			cv[BLU] = (b*NBLU)>>8;
107			/* add to histogram */
108	greg	1.1	histo[cv[RED]][cv[GRN]][cv[BLU]]++;
109	greg	1.3	/* find pixel in tree */
110	greg	1.10	for (tp = ctree, h = 0; is_branch(*tp); h++)
111			if (cv[prim(tp)] < part(tp))
112			tp += 1<<h; /* left branch */
113	greg	1.1	else
114	greg	1.15	tp += 1<<(h+1); /* right branch */
115	greg	1.10	h = pval(*tp);
116	greg	1.3	/* add to color table */
117	greg	1.10	clrtab[h].sum[RED] += r;
118			clrtab[h].sum[GRN] += g;
119			clrtab[h].sum[BLU] += b;
120			clrtab[h].n++;
121	greg	1.3	/* recompute average */
122	greg	1.10	r = clrtab[h].sum[RED] / clrtab[h].n;
123			g = clrtab[h].sum[GRN] / clrtab[h].n;
124			b = clrtab[h].sum[BLU] / clrtab[h].n;
125	greg	1.3	/* check for movement */
126	greg	1.10	if (clrtab[h].n == 1 \|\|
127			(r-clrtab[h].ent[RED])*(r-clrtab[h].ent[RED]) +
128			(g-clrtab[h].ent[GRN])*(g-clrtab[h].ent[GRN]) +
129			(b-clrtab[h].ent[BLU])*(b-clrtab[h].ent[BLU]) > MAXDST2) {
130			clrtab[h].ent[RED] = r;
131			clrtab[h].ent[GRN] = g; /* reassign pixel */
132			clrtab[h].ent[BLU] = b;
133	greg	1.12	#ifdef DEBUG
134			sprintf(errmsg, "pixel %d = (%d,%d,%d) (%d refs)\n",
135	greg	1.10	h, r, g, b, clrtab[h].n);
136	greg	1.12	eputs(errmsg);
137	greg	1.1	#endif
138	greg	1.3	(*set_pixel)(h, r, g, b);
139			}
140			return(h); /* return pixel value */
141	greg	1.1	}
142
143
144	greg	1.4	make_gmap(gam) /* make gamma correction map */
145	greg	1.1	double gam;
146			{
147			extern double pow();
148			register int i;
149
150	greg	1.4	for (i = 0; i < 256; i++)
151			clrmap[RED][i] =
152			clrmap[GRN][i] =
153	greg	1.15	clrmap[BLU][i] = 256.0 * pow((i+0.5)/256.0, 1.0/gam);
154	greg	1.4	}
155
156
157			set_cmap(rmap, gmap, bmap) /* set custom color correction map */
158			BYTE rmap, gmap, *bmap;
159			{
160	greg	1.11	bcopy((char )rmap, (char )clrmap[RED], 256);
161			bcopy((char )gmap, (char )clrmap[GRN], 256);
162			bcopy((char )bmap, (char )clrmap[BLU], 256);
163	greg	1.1	}
164
165
166	greg	1.13	map_color(rgb, col) /* map a color to a byte triplet */
167			BYTE rgb[3];
168			COLOR col;
169			{
170			rgb[RED] = map_col(col,RED);
171			rgb[GRN] = map_col(col,GRN);
172			rgb[BLU] = map_col(col,BLU);
173			}
174
175
176	greg	1.1	static
177	greg	1.7	cut(tree, level, box, c0, c1) /* partition color space */
178	greg	1.1	register CNODE *tree;
179	greg	1.7	int level;
180	greg	1.1	register int box[3][2];
181			int c0, c1;
182			{
183			int kb[3][2];
184
185	greg	1.3	if (c1-c0 <= 1) { /* assign pixel */
186	greg	1.1	*tree = set_pval(c0);
187			return;
188			}
189			/* split box */
190			*tree = split(box);
191	greg	1.11	bcopy((char )box, (char )kb, sizeof(kb));
192	greg	1.3	/* do left (lesser) branch */
193	greg	1.1	kb[prim(tree)][1] = part(tree);
194	greg	1.7	cut(tree+(1<<level), level+1, kb, c0, (c0+c1)>>1);
195	greg	1.3	/* do right branch */
196	greg	1.1	kb[prim(tree)][0] = part(tree);
197			kb[prim(tree)][1] = box[prim(tree)][1];
198	greg	1.7	cut(tree+(1<<(level+1)), level+1, kb, (c0+c1)>>1, c1);
199	greg	1.1	}
200
201
202			static int
203			split(box) /* find median cut for box */
204			register int box[3][2];
205			{
206			#define c0 r
207			register int r, g, b;
208			int pri;
209			int t[HMAX], med;
210			/* find dominant axis */
211			pri = RED;
212			if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0])
213			pri = GRN;
214			if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0])
215			pri = BLU;
216			/* sum histogram over box */
217			med = 0;
218			switch (pri) {
219			case RED:
220			for (r = box[RED][0]; r < box[RED][1]; r++) {
221			t[r] = 0;
222			for (g = box[GRN][0]; g < box[GRN][1]; g++)
223			for (b = box[BLU][0]; b < box[BLU][1]; b++)
224			t[r] += histo[r][g][b];
225			med += t[r];
226			}
227			break;
228			case GRN:
229			for (g = box[GRN][0]; g < box[GRN][1]; g++) {
230			t[g] = 0;
231			for (b = box[BLU][0]; b < box[BLU][1]; b++)
232			for (r = box[RED][0]; r < box[RED][1]; r++)
233			t[g] += histo[r][g][b];
234			med += t[g];
235			}
236			break;
237			case BLU:
238			for (b = box[BLU][0]; b < box[BLU][1]; b++) {
239			t[b] = 0;
240			for (r = box[RED][0]; r < box[RED][1]; r++)
241			for (g = box[GRN][0]; g < box[GRN][1]; g++)
242			t[b] += histo[r][g][b];
243			med += t[b];
244			}
245			break;
246			}
247			if (med < MINSAMP) /* if too sparse, split at midpoint */
248			return(set_branch(pri,(box[pri][0]+box[pri][1])>>1));
249			/* find median position */
250			med >>= 1;
251			for (c0 = box[pri][0]; med > 0; c0++)
252			med -= t[c0];
253			if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */
254			c0--; /* part left of median */
255			return(set_branch(pri,c0));
256			#undef c0
257			}