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/* Copyright (c) 1989 Regents of the University of California */ |
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|
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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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/* |
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* colortab.c - allocate and control dynamic color table. |
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* |
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* We start off with a uniform partition of color space. |
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* As pixels are sent to the frame buffer, a histogram is built. |
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* When a new color table is requested, the histogram is used |
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* to make a pseudo-optimal partition, after which the |
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* histogram is cleared. This algorithm |
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* performs only as well as the next drawing's color |
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* distribution is correlated to the last. |
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*/ |
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|
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#include "color.h" |
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|
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#define NULL 0 |
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/* histogram resolution */ |
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#define NRED 24 |
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#define NGRN 32 |
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#define NBLU 16 |
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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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/* maximum distance^2 before color reassign */ |
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#define MAXDST2 5 |
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/* maximum frame buffer depth */ |
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#define FBDEPTH 8 |
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/* color map resolution */ |
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#define MAPSIZ 256 |
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/* map a color */ |
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#define map_col(c,p) clrmap[ colval(c,p)<1. ? \ |
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(int)(colval(c,p)*MAPSIZ) : MAPSIZ-1 ] |
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/* color partition tree */ |
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#define CNODE short |
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#define set_branch(p,c) ((c)<<2|(p)) |
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#define set_pval(pv) ((pv)<<2|3) |
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#define is_pval(cn) (((cn)&3)==3) |
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#define part(cn) ((cn)>>2) |
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#define prim(cn) ((cn)&3) |
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#define pval(cn) ((cn)>>2) |
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/* our color table */ |
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struct tabent { |
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long sum[3]; /* sum of colors using this entry */ |
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long n; /* number of colors */ |
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short ent[3]; /* current table value */ |
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} clrtab[1<<FBDEPTH]; |
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/* our color correction map */ |
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static BYTE clrmap[MAPSIZ]; |
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/* histogram of colors used */ |
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static unsigned histo[NRED][NGRN][NBLU]; |
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/* initial color cube boundaries */ |
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static int CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU}; |
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/* color cube partition */ |
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static CNODE ctree[1<<(FBDEPTH+1)]; |
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/* callback for pixel assignment */ |
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static int (*set_pixel)(); |
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|
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|
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int |
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new_ctab(ncolors, cset) /* start new color table with max ncolors */ |
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int ncolors; |
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int (*cset)(); |
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{ |
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if (ncolors < 1 || ncolors > 1<<FBDEPTH || cset == NULL) |
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return(0); |
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/* assign pixel callback routine */ |
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set_pixel = cset; |
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/* clear color table */ |
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bzero(clrtab, sizeof(clrtab)); |
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/* partition color space */ |
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cut(ctree, FBDEPTH, CLRCUBE, 0, ncolors); |
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/* clear histogram */ |
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bzero(histo, sizeof(histo)); |
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/* return number of colors used */ |
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return(ncolors); |
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} |
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|
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|
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int |
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get_pixel(col) /* get pixel for color */ |
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COLOR col; |
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{ |
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int r, g, b; |
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int cv[3]; |
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register union { CNODE *t; struct tabent *e; } p; |
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register int h; |
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/* map color */ |
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r = map_col(col,RED); |
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g = map_col(col,GRN); |
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b = map_col(col,BLU); |
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/* reduce resolution */ |
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cv[RED] = (r*NRED)>>8; |
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cv[GRN] = (g*NGRN)>>8; |
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cv[BLU] = (b*NBLU)>>8; |
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/* add to histogram */ |
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histo[cv[RED]][cv[GRN]][cv[BLU]]++; |
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/* find pixel in tree */ |
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p.t = ctree; |
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for (h = FBDEPTH; h > 0; h--) { |
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if (is_pval(*p.t)) |
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break; |
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if (cv[prim(*p.t)] < part(*p.t)) |
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p.t++; /* left branch */ |
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else |
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p.t += 1<<h; /* right branch */ |
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} |
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h = pval(*p.t); |
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/* add to color table */ |
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p.e = clrtab + h; |
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/* add to sum */ |
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p.e->sum[RED] += r; |
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p.e->sum[GRN] += g; |
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p.e->sum[BLU] += b; |
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p.e->n++; |
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/* recompute average */ |
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r = p.e->sum[RED] / p.e->n; |
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g = p.e->sum[GRN] / p.e->n; |
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b = p.e->sum[BLU] / p.e->n; |
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/* check for movement */ |
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if (p.e->n == 1 || |
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(r-p.e->ent[RED])*(r-p.e->ent[RED]) + |
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(g-p.e->ent[GRN])*(g-p.e->ent[GRN]) + |
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(b-p.e->ent[BLU])*(b-p.e->ent[BLU]) > MAXDST2) { |
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p.e->ent[RED] = r; |
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p.e->ent[GRN] = g; /* reassign pixel */ |
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p.e->ent[BLU] = b; |
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#ifdef notdef |
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printf("pixel %d = (%d,%d,%d) (%d refs)\n", |
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h, r, g, b, p.e->n); |
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#endif |
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(*set_pixel)(h, r, g, b); |
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} |
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return(h); /* return pixel value */ |
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} |
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|
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|
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make_cmap(gam) /* make gamma correction map */ |
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double gam; |
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{ |
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extern double pow(); |
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register int i; |
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|
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for (i = 0; i < MAPSIZ; i++) |
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clrmap[i] = 256.0 * pow(i/(double)MAPSIZ, 1.0/gam); |
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} |
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|
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|
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static |
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cut(tree, height, box, c0, c1) /* partition color space */ |
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register CNODE *tree; |
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int height; |
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register int box[3][2]; |
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int c0, c1; |
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{ |
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int kb[3][2]; |
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|
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if (c1-c0 <= 1) { /* assign pixel */ |
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*tree = set_pval(c0); |
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return; |
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} |
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/* split box */ |
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*tree = split(box); |
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bcopy(box, kb, sizeof(kb)); |
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/* do left (lesser) branch */ |
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kb[prim(*tree)][1] = part(*tree); |
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cut(tree+1, height-1, kb, c0, (c0+c1)>>1); |
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/* do right branch */ |
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kb[prim(*tree)][0] = part(*tree); |
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kb[prim(*tree)][1] = box[prim(*tree)][1]; |
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cut(tree+(1<<height), height-1, kb, (c0+c1)>>1, c1); |
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} |
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|
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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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int t[HMAX], med; |
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/* 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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med += t[b]; |
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} |
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break; |
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} |
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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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/* 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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#undef c0 |
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} |
