1 |
greg |
2.1 |
#ifndef lint |
2 |
greg |
2.12 |
static const char RCSid[] = "$Id$"; |
3 |
greg |
2.1 |
#endif |
4 |
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/* |
5 |
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* Simple median-cut color quantization based on colortab.c |
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*/ |
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#include "standard.h" |
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#include "color.h" |
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/* histogram resolution */ |
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#define NRED 36 |
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#define NGRN 48 |
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#define NBLU 24 |
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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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/* color partition */ |
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#define set_branch(p,c) ((c)<<2|(p)) |
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#define part(cn) ((cn)>>2) |
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#define prim(cn) ((cn)&3) |
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/* our color table (global) */ |
23 |
greg |
2.10 |
extern BYTE clrtab[256][3]; |
24 |
greg |
2.1 |
/* histogram of colors / color assignments */ |
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static unsigned histo[NRED][NGRN][NBLU]; |
26 |
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#define cndx(c) histo[((c)[RED]*NRED)>>8][((c)[GRN]*NGRN)>>8][((c)[BLU]*NBLU)>>8] |
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/* initial color cube boundary */ |
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static int CLRCUBE[3][2] = {0,NRED,0,NGRN,0,NBLU}; |
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/* maximum propagated error during dithering */ |
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#define MAXERR 20 |
31 |
greg |
2.2 |
/* define CLOSEST to get closest colors */ |
32 |
greg |
2.4 |
#ifndef CLOSEST |
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#ifdef SPEED |
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#if SPEED > 8 |
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#define CLOSEST 1 /* this step takes a little longer */ |
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#endif |
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#endif |
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#endif |
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greg |
2.1 |
|
40 |
greg |
2.11 |
static cut(), mktabent(), closest(), addneigh(), setclosest(); |
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static int split(); |
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static unsigned dist(); |
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44 |
greg |
2.1 |
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45 |
greg |
2.10 |
new_histo(n) /* clear our histogram */ |
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int n; |
47 |
greg |
2.1 |
{ |
48 |
greg |
2.14 |
bzero((void *)histo, sizeof(histo)); |
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greg |
2.10 |
return(0); |
50 |
greg |
2.1 |
} |
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cnt_pixel(col) /* add pixel to our histogram */ |
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register BYTE col[]; |
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{ |
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cndx(col)++; |
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} |
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cnt_colrs(cs, n) /* add a scanline to our histogram */ |
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register COLR *cs; |
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register int n; |
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{ |
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while (n-- > 0) { |
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cndx(cs[0])++; |
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cs++; |
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} |
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} |
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new_clrtab(ncolors) /* make new color table using ncolors */ |
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int ncolors; |
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{ |
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if (ncolors < 1) |
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return(0); |
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if (ncolors > 256) |
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ncolors = 256; |
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/* partition color space */ |
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cut(CLRCUBE, 0, ncolors); |
80 |
greg |
2.2 |
#ifdef CLOSEST |
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closest(ncolors); /* ensure colors picked are closest */ |
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#endif |
83 |
greg |
2.9 |
/* reset dithering function */ |
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dith_colrs((BYTE *)NULL, (COLR *)NULL, 0); |
85 |
greg |
2.1 |
/* return new color table size */ |
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return(ncolors); |
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} |
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90 |
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int |
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map_pixel(col) /* get pixel for color */ |
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register BYTE col[]; |
93 |
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{ |
94 |
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return(cndx(col)); |
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} |
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map_colrs(bs, cs, n) /* convert a scanline to color index values */ |
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register BYTE *bs; |
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register COLR *cs; |
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register int n; |
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{ |
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while (n-- > 0) { |
104 |
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*bs++ = cndx(cs[0]); |
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cs++; |
106 |
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} |
107 |
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} |
108 |
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109 |
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110 |
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dith_colrs(bs, cs, n) /* convert scanline to dithered index values */ |
111 |
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register BYTE *bs; |
112 |
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register COLR *cs; |
113 |
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int n; |
114 |
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{ |
115 |
greg |
2.8 |
static short (*cerr)[3] = NULL; |
116 |
greg |
2.1 |
static int N = 0; |
117 |
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int err[3], errp[3]; |
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register int x, i; |
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120 |
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if (n != N) { /* get error propogation array */ |
121 |
greg |
2.8 |
if (N) { |
122 |
greg |
2.12 |
free((void *)cerr); |
123 |
greg |
2.8 |
cerr = NULL; |
124 |
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} |
125 |
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if (n) |
126 |
greg |
2.1 |
cerr = (short (*)[3])malloc(3*n*sizeof(short)); |
127 |
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if (cerr == NULL) { |
128 |
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N = 0; |
129 |
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map_colrs(bs, cs, n); |
130 |
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return; |
131 |
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} |
132 |
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N = n; |
133 |
greg |
2.14 |
bzero((void *)cerr, 3*N*sizeof(short)); |
134 |
greg |
2.1 |
} |
135 |
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err[0] = err[1] = err[2] = 0; |
136 |
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for (x = 0; x < n; x++) { |
137 |
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for (i = 0; i < 3; i++) { /* dither value */ |
138 |
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errp[i] = err[i]; |
139 |
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err[i] += cerr[x][i]; |
140 |
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#ifdef MAXERR |
141 |
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if (err[i] > MAXERR) err[i] = MAXERR; |
142 |
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else if (err[i] < -MAXERR) err[i] = -MAXERR; |
143 |
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#endif |
144 |
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err[i] += cs[x][i]; |
145 |
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if (err[i] < 0) err[i] = 0; |
146 |
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else if (err[i] > 255) err[i] = 255; |
147 |
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} |
148 |
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bs[x] = cndx(err); |
149 |
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for (i = 0; i < 3; i++) { /* propagate error */ |
150 |
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err[i] -= clrtab[bs[x]][i]; |
151 |
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err[i] /= 3; |
152 |
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cerr[x][i] = err[i] + errp[i]; |
153 |
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} |
154 |
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} |
155 |
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} |
156 |
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157 |
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158 |
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static |
159 |
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cut(box, c0, c1) /* partition color space */ |
160 |
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register int box[3][2]; |
161 |
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int c0, c1; |
162 |
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{ |
163 |
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register int branch; |
164 |
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int kb[3][2]; |
165 |
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166 |
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if (c1-c0 <= 1) { /* assign pixel */ |
167 |
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mktabent(c0, box); |
168 |
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return; |
169 |
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} |
170 |
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/* split box */ |
171 |
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branch = split(box); |
172 |
greg |
2.14 |
bcopy((void *)box, (void *)kb, sizeof(kb)); |
173 |
greg |
2.1 |
/* do left (lesser) branch */ |
174 |
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kb[prim(branch)][1] = part(branch); |
175 |
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cut(kb, c0, (c0+c1)>>1); |
176 |
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/* do right branch */ |
177 |
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kb[prim(branch)][0] = part(branch); |
178 |
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kb[prim(branch)][1] = box[prim(branch)][1]; |
179 |
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cut(kb, (c0+c1)>>1, c1); |
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} |
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182 |
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183 |
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static int |
184 |
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split(box) /* find median cut for box */ |
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register int box[3][2]; |
186 |
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{ |
187 |
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#define c0 r |
188 |
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register int r, g, b; |
189 |
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int pri; |
190 |
greg |
2.6 |
long t[HMAX], med; |
191 |
greg |
2.1 |
/* find dominant axis */ |
192 |
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pri = RED; |
193 |
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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; |
197 |
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/* sum histogram over box */ |
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med = 0; |
199 |
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switch (pri) { |
200 |
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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; |
203 |
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for (g = box[GRN][0]; g < box[GRN][1]; g++) |
204 |
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for (b = box[BLU][0]; b < box[BLU][1]; b++) |
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t[r] += histo[r][g][b]; |
206 |
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med += t[r]; |
207 |
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} |
208 |
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break; |
209 |
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case GRN: |
210 |
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for (g = box[GRN][0]; g < box[GRN][1]; g++) { |
211 |
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t[g] = 0; |
212 |
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for (b = box[BLU][0]; b < box[BLU][1]; b++) |
213 |
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for (r = box[RED][0]; r < box[RED][1]; r++) |
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t[g] += histo[r][g][b]; |
215 |
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med += t[g]; |
216 |
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} |
217 |
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break; |
218 |
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case BLU: |
219 |
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for (b = box[BLU][0]; b < box[BLU][1]; b++) { |
220 |
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t[b] = 0; |
221 |
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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++) |
223 |
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t[b] += histo[r][g][b]; |
224 |
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med += t[b]; |
225 |
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} |
226 |
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break; |
227 |
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} |
228 |
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if (med < MINSAMP) /* if too sparse, split at midpoint */ |
229 |
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return(set_branch(pri,(box[pri][0]+box[pri][1])>>1)); |
230 |
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/* find median position */ |
231 |
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med >>= 1; |
232 |
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for (c0 = box[pri][0]; med > 0; c0++) |
233 |
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med -= t[c0]; |
234 |
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if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */ |
235 |
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c0--; /* part left of median */ |
236 |
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return(set_branch(pri,c0)); |
237 |
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#undef c0 |
238 |
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} |
239 |
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240 |
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241 |
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static |
242 |
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mktabent(p, box) /* compute average color for box and assign */ |
243 |
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int p; |
244 |
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register int box[3][2]; |
245 |
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{ |
246 |
greg |
2.5 |
unsigned long sum[3]; |
247 |
greg |
2.7 |
unsigned r, g; |
248 |
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unsigned long n; |
249 |
greg |
2.5 |
register unsigned b, c; |
250 |
greg |
2.1 |
/* sum pixels in box */ |
251 |
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n = 0; |
252 |
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sum[RED] = sum[GRN] = sum[BLU] = 0; |
253 |
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for (r = box[RED][0]; r < box[RED][1]; r++) |
254 |
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for (g = box[GRN][0]; g < box[GRN][1]; g++) |
255 |
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for (b = box[BLU][0]; b < box[BLU][1]; b++) { |
256 |
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if (c = histo[r][g][b]) { |
257 |
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n += c; |
258 |
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sum[RED] += (long)c*r; |
259 |
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sum[GRN] += (long)c*g; |
260 |
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sum[BLU] += (long)c*b; |
261 |
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} |
262 |
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histo[r][g][b] = p; /* assign pixel */ |
263 |
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} |
264 |
greg |
2.7 |
if (n >= (1L<<23)/HMAX) { /* avoid overflow */ |
265 |
greg |
2.5 |
sum[RED] /= n; |
266 |
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sum[GRN] /= n; |
267 |
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sum[BLU] /= n; |
268 |
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n = 1; |
269 |
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} |
270 |
greg |
2.1 |
if (n) { /* compute average */ |
271 |
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clrtab[p][RED] = sum[RED]*256/NRED/n; |
272 |
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clrtab[p][GRN] = sum[GRN]*256/NGRN/n; |
273 |
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clrtab[p][BLU] = sum[BLU]*256/NBLU/n; |
274 |
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} else { /* empty box -- use midpoint */ |
275 |
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clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2; |
276 |
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clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2; |
277 |
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clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2; |
278 |
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} |
279 |
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} |
280 |
greg |
2.2 |
|
281 |
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282 |
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#ifdef CLOSEST |
283 |
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#define NBSIZ 32 |
284 |
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static |
285 |
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closest(n) /* make sure we have the closest colors */ |
286 |
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int n; |
287 |
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{ |
288 |
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BYTE *neigh[256]; |
289 |
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register int r, g, b; |
290 |
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#define i r |
291 |
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/* get space for neighbor lists */ |
292 |
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for (i = 0; i < n; i++) { |
293 |
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if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) { |
294 |
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while (i--) |
295 |
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free(neigh[i]); |
296 |
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return; /* ENOMEM -- abandon effort */ |
297 |
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} |
298 |
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neigh[i][0] = i; /* identity is terminator */ |
299 |
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} |
300 |
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/* make neighbor lists */ |
301 |
greg |
2.3 |
for (r = 0; r < NRED; r++) |
302 |
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for (g = 0; g < NGRN; g++) |
303 |
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for (b = 0; b < NBLU; b++) { |
304 |
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if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b]) |
305 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r+1][g][b]); |
306 |
greg |
2.3 |
if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b]) |
307 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r][g+1][b]); |
308 |
greg |
2.3 |
if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1]) |
309 |
greg |
2.2 |
addneigh(neigh, histo[r][g][b], histo[r][g][b+1]); |
310 |
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} |
311 |
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/* assign closest values */ |
312 |
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for (r = 0; r < NRED; r++) |
313 |
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for (g = 0; g < NGRN; g++) |
314 |
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for (b = 0; b < NBLU; b++) |
315 |
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setclosest(neigh, r, g, b); |
316 |
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/* free neighbor lists */ |
317 |
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for (i = 0; i < n; i++) |
318 |
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free(neigh[i]); |
319 |
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#undef i |
320 |
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} |
321 |
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322 |
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323 |
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static |
324 |
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addneigh(nl, i, j) /* i and j are neighbors; add them to list */ |
325 |
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register BYTE *nl[]; |
326 |
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register int i; |
327 |
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int j; |
328 |
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{ |
329 |
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int nc; |
330 |
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char *nnl; |
331 |
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register int t; |
332 |
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333 |
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for (nc = 0; nc < 2; nc++) { /* do both neighbors */ |
334 |
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for (t = 0; nl[i][t] != i; t++) |
335 |
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if (nl[i][t] == j) |
336 |
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break; /* in list already */ |
337 |
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if (nl[i][t] == i) { /* add to list */ |
338 |
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nl[i][t++] = j; |
339 |
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if (t % NBSIZ == 0) { /* enlarge list */ |
340 |
greg |
2.13 |
if ((nnl = realloc((void *)nl[i], |
341 |
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t+NBSIZ)) == NULL) |
342 |
greg |
2.2 |
t--; |
343 |
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else |
344 |
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nl[i] = (BYTE *)nnl; |
345 |
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} |
346 |
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nl[i][t] = i; /* terminator */ |
347 |
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} |
348 |
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t = i; i = j; j = t; /* swap and do it again */ |
349 |
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} |
350 |
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} |
351 |
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352 |
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353 |
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static unsigned |
354 |
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dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */ |
355 |
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register BYTE col[3]; |
356 |
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int r, g, b; |
357 |
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{ |
358 |
greg |
2.4 |
register int tmp; |
359 |
greg |
2.2 |
register unsigned sum; |
360 |
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361 |
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tmp = col[RED]*NRED/256 - r; |
362 |
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sum = tmp*tmp; |
363 |
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tmp = col[GRN]*NGRN/256 - g; |
364 |
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sum += tmp*tmp; |
365 |
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tmp = col[BLU]*NBLU/256 - b; |
366 |
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sum += tmp*tmp; |
367 |
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return(sum); |
368 |
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} |
369 |
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370 |
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371 |
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static |
372 |
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setclosest(nl, r, g, b) /* find index closest to color and assign */ |
373 |
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BYTE *nl[]; |
374 |
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int r, g, b; |
375 |
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{ |
376 |
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int ident; |
377 |
|
|
unsigned min; |
378 |
|
|
register unsigned d; |
379 |
|
|
register BYTE *p; |
380 |
|
|
/* get starting value */ |
381 |
|
|
min = dist(clrtab[ident=histo[r][g][b]], r, g, b); |
382 |
|
|
/* find minimum */ |
383 |
|
|
for (p = nl[ident]; *p != ident; p++) |
384 |
|
|
if ((d = dist(clrtab[*p], r, g, b)) < min) { |
385 |
|
|
min = d; |
386 |
|
|
histo[r][g][b] = *p; |
387 |
|
|
} |
388 |
|
|
} |
389 |
|
|
#endif |