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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 18 |
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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 frame buffer depth */ |
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#define FBDEPTH 8 |
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/* color map resolution */ |
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#define MAPSIZ 128 |
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/* map a color */ |
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#define map_col(c,p) clrmap[p][ 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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COLR clrtab[1<<FBDEPTH]; |
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/* our color correction map */ |
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static BYTE clrmap[3][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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|
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|
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COLR * |
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get_ctab(ncolors) /* assign a color table with max ncolors */ |
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int ncolors; |
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{ |
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if (ncolors < 1 || ncolors > 1<<FBDEPTH) |
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return(NULL); |
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/* partition color table */ |
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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 color table */ |
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return(clrtab); |
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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 cv[3]; |
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register CNODE *tp; |
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register int h; |
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/* map color */ |
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cv[RED] = map_col(col,RED); |
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cv[GRN] = map_col(col,GRN); |
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cv[BLU] = map_col(col,BLU); |
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/* add to histogram */ |
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histo[cv[RED]][cv[GRN]][cv[BLU]]++; |
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/* find pixel value in tree */ |
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tp = ctree; |
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for (h = FBDEPTH; h > 0; h--) { |
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if (is_pval(*tp)) |
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break; |
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if (cv[prim(*tp)] < part(*tp)) |
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tp++; /* left branch */ |
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else |
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tp += 1<<h; /* right branch */ |
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} |
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#ifdef notdef |
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printf("distance (%d,%d,%d)\n", |
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cv[RED] - clrtab[pval(*tp)][RED]*NRED/256, |
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cv[GRN] - clrtab[pval(*tp)][GRN]*NGRN/256, |
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cv[BLU] - clrtab[pval(*tp)][BLU]*NBLU/256); |
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#endif |
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return(pval(*tp)); |
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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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double d; |
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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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d = pow(i/(double)MAPSIZ, 1.0/gam); |
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clrmap[RED][i] = d * NRED; |
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clrmap[GRN][i] = d * NGRN; |
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clrmap[BLU][i] = d * NBLU; |
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} |
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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 color */ |
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clrtab[c0][RED] = ((box[RED][0]+box[RED][1])<<7)/NRED; |
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clrtab[c0][GRN] = ((box[GRN][0]+box[GRN][1])<<7)/NGRN; |
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clrtab[c0][BLU] = ((box[BLU][0]+box[BLU][1])<<7)/NBLU; |
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clrtab[c0][EXP] = COLXS; |
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*tree = set_pval(c0); |
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#ifdef notdef |
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printf("final box size = (%d,%d,%d)\n", |
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box[RED][1] - box[RED][0], |
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box[GRN][1] - box[GRN][0], |
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box[BLU][1] - box[BLU][0]); |
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#endif |
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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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kb[prim(*tree)][1] = part(*tree); |
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cut(tree+1, height-1, kb, c0, (c0+c1)>>1); /* lesser */ |
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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); /* greater */ |
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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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} |
