| 1 |
/* Copyright (c) 1993 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 |
/* define CLOSEST to get closest colors */ |
| 35 |
#ifndef CLOSEST |
| 36 |
#ifdef SPEED |
| 37 |
#if SPEED > 8 |
| 38 |
#define CLOSEST 1 /* this step takes a little longer */ |
| 39 |
#endif |
| 40 |
#endif |
| 41 |
#endif |
| 42 |
|
| 43 |
|
| 44 |
new_histo() /* clear our histogram */ |
| 45 |
{ |
| 46 |
bzero((char *)histo, sizeof(histo)); |
| 47 |
} |
| 48 |
|
| 49 |
|
| 50 |
cnt_pixel(col) /* add pixel to our histogram */ |
| 51 |
register BYTE col[]; |
| 52 |
{ |
| 53 |
cndx(col)++; |
| 54 |
} |
| 55 |
|
| 56 |
|
| 57 |
cnt_colrs(cs, n) /* add a scanline to our histogram */ |
| 58 |
register COLR *cs; |
| 59 |
register int n; |
| 60 |
{ |
| 61 |
while (n-- > 0) { |
| 62 |
cndx(cs[0])++; |
| 63 |
cs++; |
| 64 |
} |
| 65 |
} |
| 66 |
|
| 67 |
|
| 68 |
new_clrtab(ncolors) /* make new color table using ncolors */ |
| 69 |
int ncolors; |
| 70 |
{ |
| 71 |
if (ncolors < 1) |
| 72 |
return(0); |
| 73 |
if (ncolors > 256) |
| 74 |
ncolors = 256; |
| 75 |
/* partition color space */ |
| 76 |
cut(CLRCUBE, 0, ncolors); |
| 77 |
#ifdef CLOSEST |
| 78 |
closest(ncolors); /* ensure colors picked are closest */ |
| 79 |
#endif |
| 80 |
/* return new color table size */ |
| 81 |
return(ncolors); |
| 82 |
} |
| 83 |
|
| 84 |
|
| 85 |
int |
| 86 |
map_pixel(col) /* get pixel for color */ |
| 87 |
register BYTE col[]; |
| 88 |
{ |
| 89 |
return(cndx(col)); |
| 90 |
} |
| 91 |
|
| 92 |
|
| 93 |
map_colrs(bs, cs, n) /* convert a scanline to color index values */ |
| 94 |
register BYTE *bs; |
| 95 |
register COLR *cs; |
| 96 |
register int n; |
| 97 |
{ |
| 98 |
while (n-- > 0) { |
| 99 |
*bs++ = cndx(cs[0]); |
| 100 |
cs++; |
| 101 |
} |
| 102 |
} |
| 103 |
|
| 104 |
|
| 105 |
dith_colrs(bs, cs, n) /* convert scanline to dithered index values */ |
| 106 |
register BYTE *bs; |
| 107 |
register COLR *cs; |
| 108 |
int n; |
| 109 |
{ |
| 110 |
static short (*cerr)[3]; |
| 111 |
static int N = 0; |
| 112 |
int err[3], errp[3]; |
| 113 |
register int x, i; |
| 114 |
|
| 115 |
if (n != N) { /* get error propogation array */ |
| 116 |
if (N) |
| 117 |
cerr = (short (*)[3])realloc((char *)cerr, |
| 118 |
3*n*sizeof(short)); |
| 119 |
else |
| 120 |
cerr = (short (*)[3])malloc(3*n*sizeof(short)); |
| 121 |
if (cerr == NULL) { |
| 122 |
N = 0; |
| 123 |
map_colrs(bs, cs, n); |
| 124 |
return; |
| 125 |
} |
| 126 |
N = n; |
| 127 |
bzero((char *)cerr, 3*N*sizeof(short)); |
| 128 |
} |
| 129 |
err[0] = err[1] = err[2] = 0; |
| 130 |
for (x = 0; x < n; x++) { |
| 131 |
for (i = 0; i < 3; i++) { /* dither value */ |
| 132 |
errp[i] = err[i]; |
| 133 |
err[i] += cerr[x][i]; |
| 134 |
#ifdef MAXERR |
| 135 |
if (err[i] > MAXERR) err[i] = MAXERR; |
| 136 |
else if (err[i] < -MAXERR) err[i] = -MAXERR; |
| 137 |
#endif |
| 138 |
err[i] += cs[x][i]; |
| 139 |
if (err[i] < 0) err[i] = 0; |
| 140 |
else if (err[i] > 255) err[i] = 255; |
| 141 |
} |
| 142 |
bs[x] = cndx(err); |
| 143 |
for (i = 0; i < 3; i++) { /* propagate error */ |
| 144 |
err[i] -= clrtab[bs[x]][i]; |
| 145 |
err[i] /= 3; |
| 146 |
cerr[x][i] = err[i] + errp[i]; |
| 147 |
} |
| 148 |
} |
| 149 |
} |
| 150 |
|
| 151 |
|
| 152 |
static |
| 153 |
cut(box, c0, c1) /* partition color space */ |
| 154 |
register int box[3][2]; |
| 155 |
int c0, c1; |
| 156 |
{ |
| 157 |
register int branch; |
| 158 |
int kb[3][2]; |
| 159 |
|
| 160 |
if (c1-c0 <= 1) { /* assign pixel */ |
| 161 |
mktabent(c0, box); |
| 162 |
return; |
| 163 |
} |
| 164 |
/* split box */ |
| 165 |
branch = split(box); |
| 166 |
bcopy((char *)box, (char *)kb, sizeof(kb)); |
| 167 |
/* do left (lesser) branch */ |
| 168 |
kb[prim(branch)][1] = part(branch); |
| 169 |
cut(kb, c0, (c0+c1)>>1); |
| 170 |
/* do right branch */ |
| 171 |
kb[prim(branch)][0] = part(branch); |
| 172 |
kb[prim(branch)][1] = box[prim(branch)][1]; |
| 173 |
cut(kb, (c0+c1)>>1, c1); |
| 174 |
} |
| 175 |
|
| 176 |
|
| 177 |
static int |
| 178 |
split(box) /* find median cut for box */ |
| 179 |
register int box[3][2]; |
| 180 |
{ |
| 181 |
#define c0 r |
| 182 |
register int r, g, b; |
| 183 |
int pri; |
| 184 |
long t[HMAX], med; |
| 185 |
/* find dominant axis */ |
| 186 |
pri = RED; |
| 187 |
if (box[GRN][1]-box[GRN][0] > box[pri][1]-box[pri][0]) |
| 188 |
pri = GRN; |
| 189 |
if (box[BLU][1]-box[BLU][0] > box[pri][1]-box[pri][0]) |
| 190 |
pri = BLU; |
| 191 |
/* sum histogram over box */ |
| 192 |
med = 0; |
| 193 |
switch (pri) { |
| 194 |
case RED: |
| 195 |
for (r = box[RED][0]; r < box[RED][1]; r++) { |
| 196 |
t[r] = 0; |
| 197 |
for (g = box[GRN][0]; g < box[GRN][1]; g++) |
| 198 |
for (b = box[BLU][0]; b < box[BLU][1]; b++) |
| 199 |
t[r] += histo[r][g][b]; |
| 200 |
med += t[r]; |
| 201 |
} |
| 202 |
break; |
| 203 |
case GRN: |
| 204 |
for (g = box[GRN][0]; g < box[GRN][1]; g++) { |
| 205 |
t[g] = 0; |
| 206 |
for (b = box[BLU][0]; b < box[BLU][1]; b++) |
| 207 |
for (r = box[RED][0]; r < box[RED][1]; r++) |
| 208 |
t[g] += histo[r][g][b]; |
| 209 |
med += t[g]; |
| 210 |
} |
| 211 |
break; |
| 212 |
case BLU: |
| 213 |
for (b = box[BLU][0]; b < box[BLU][1]; b++) { |
| 214 |
t[b] = 0; |
| 215 |
for (r = box[RED][0]; r < box[RED][1]; r++) |
| 216 |
for (g = box[GRN][0]; g < box[GRN][1]; g++) |
| 217 |
t[b] += histo[r][g][b]; |
| 218 |
med += t[b]; |
| 219 |
} |
| 220 |
break; |
| 221 |
} |
| 222 |
if (med < MINSAMP) /* if too sparse, split at midpoint */ |
| 223 |
return(set_branch(pri,(box[pri][0]+box[pri][1])>>1)); |
| 224 |
/* find median position */ |
| 225 |
med >>= 1; |
| 226 |
for (c0 = box[pri][0]; med > 0; c0++) |
| 227 |
med -= t[c0]; |
| 228 |
if (c0 > (box[pri][0]+box[pri][1])>>1) /* if past the midpoint */ |
| 229 |
c0--; /* part left of median */ |
| 230 |
return(set_branch(pri,c0)); |
| 231 |
#undef c0 |
| 232 |
} |
| 233 |
|
| 234 |
|
| 235 |
static |
| 236 |
mktabent(p, box) /* compute average color for box and assign */ |
| 237 |
int p; |
| 238 |
register int box[3][2]; |
| 239 |
{ |
| 240 |
unsigned long sum[3]; |
| 241 |
unsigned r, g; |
| 242 |
unsigned long n; |
| 243 |
register unsigned b, c; |
| 244 |
/* sum pixels in box */ |
| 245 |
n = 0; |
| 246 |
sum[RED] = sum[GRN] = sum[BLU] = 0; |
| 247 |
for (r = box[RED][0]; r < box[RED][1]; r++) |
| 248 |
for (g = box[GRN][0]; g < box[GRN][1]; g++) |
| 249 |
for (b = box[BLU][0]; b < box[BLU][1]; b++) { |
| 250 |
if (c = histo[r][g][b]) { |
| 251 |
n += c; |
| 252 |
sum[RED] += (long)c*r; |
| 253 |
sum[GRN] += (long)c*g; |
| 254 |
sum[BLU] += (long)c*b; |
| 255 |
} |
| 256 |
histo[r][g][b] = p; /* assign pixel */ |
| 257 |
} |
| 258 |
if (n >= (1L<<23)/HMAX) { /* avoid overflow */ |
| 259 |
sum[RED] /= n; |
| 260 |
sum[GRN] /= n; |
| 261 |
sum[BLU] /= n; |
| 262 |
n = 1; |
| 263 |
} |
| 264 |
if (n) { /* compute average */ |
| 265 |
clrtab[p][RED] = sum[RED]*256/NRED/n; |
| 266 |
clrtab[p][GRN] = sum[GRN]*256/NGRN/n; |
| 267 |
clrtab[p][BLU] = sum[BLU]*256/NBLU/n; |
| 268 |
} else { /* empty box -- use midpoint */ |
| 269 |
clrtab[p][RED] = (box[RED][0]+box[RED][1])*256/NRED/2; |
| 270 |
clrtab[p][GRN] = (box[GRN][0]+box[GRN][1])*256/NGRN/2; |
| 271 |
clrtab[p][BLU] = (box[BLU][0]+box[BLU][1])*256/NBLU/2; |
| 272 |
} |
| 273 |
} |
| 274 |
|
| 275 |
|
| 276 |
#ifdef CLOSEST |
| 277 |
#define NBSIZ 32 |
| 278 |
static |
| 279 |
closest(n) /* make sure we have the closest colors */ |
| 280 |
int n; |
| 281 |
{ |
| 282 |
BYTE *neigh[256]; |
| 283 |
register int r, g, b; |
| 284 |
#define i r |
| 285 |
/* get space for neighbor lists */ |
| 286 |
for (i = 0; i < n; i++) { |
| 287 |
if ((neigh[i] = (BYTE *)malloc(NBSIZ)) == NULL) { |
| 288 |
while (i--) |
| 289 |
free(neigh[i]); |
| 290 |
return; /* ENOMEM -- abandon effort */ |
| 291 |
} |
| 292 |
neigh[i][0] = i; /* identity is terminator */ |
| 293 |
} |
| 294 |
/* make neighbor lists */ |
| 295 |
for (r = 0; r < NRED; r++) |
| 296 |
for (g = 0; g < NGRN; g++) |
| 297 |
for (b = 0; b < NBLU; b++) { |
| 298 |
if (r < NRED-1 && histo[r][g][b] != histo[r+1][g][b]) |
| 299 |
addneigh(neigh, histo[r][g][b], histo[r+1][g][b]); |
| 300 |
if (g < NGRN-1 && histo[r][g][b] != histo[r][g+1][b]) |
| 301 |
addneigh(neigh, histo[r][g][b], histo[r][g+1][b]); |
| 302 |
if (b < NBLU-1 && histo[r][g][b] != histo[r][g][b+1]) |
| 303 |
addneigh(neigh, histo[r][g][b], histo[r][g][b+1]); |
| 304 |
} |
| 305 |
/* assign closest values */ |
| 306 |
for (r = 0; r < NRED; r++) |
| 307 |
for (g = 0; g < NGRN; g++) |
| 308 |
for (b = 0; b < NBLU; b++) |
| 309 |
setclosest(neigh, r, g, b); |
| 310 |
/* free neighbor lists */ |
| 311 |
for (i = 0; i < n; i++) |
| 312 |
free(neigh[i]); |
| 313 |
#undef i |
| 314 |
} |
| 315 |
|
| 316 |
|
| 317 |
static |
| 318 |
addneigh(nl, i, j) /* i and j are neighbors; add them to list */ |
| 319 |
register BYTE *nl[]; |
| 320 |
register int i; |
| 321 |
int j; |
| 322 |
{ |
| 323 |
int nc; |
| 324 |
char *nnl; |
| 325 |
register int t; |
| 326 |
|
| 327 |
for (nc = 0; nc < 2; nc++) { /* do both neighbors */ |
| 328 |
for (t = 0; nl[i][t] != i; t++) |
| 329 |
if (nl[i][t] == j) |
| 330 |
break; /* in list already */ |
| 331 |
if (nl[i][t] == i) { /* add to list */ |
| 332 |
nl[i][t++] = j; |
| 333 |
if (t % NBSIZ == 0) { /* enlarge list */ |
| 334 |
if ((nnl = realloc(nl[i], t+NBSIZ)) == NULL) |
| 335 |
t--; |
| 336 |
else |
| 337 |
nl[i] = (BYTE *)nnl; |
| 338 |
} |
| 339 |
nl[i][t] = i; /* terminator */ |
| 340 |
} |
| 341 |
t = i; i = j; j = t; /* swap and do it again */ |
| 342 |
} |
| 343 |
} |
| 344 |
|
| 345 |
|
| 346 |
static unsigned |
| 347 |
dist(col, r, g, b) /* find distance from clrtab entry to r,g,b */ |
| 348 |
register BYTE col[3]; |
| 349 |
int r, g, b; |
| 350 |
{ |
| 351 |
register int tmp; |
| 352 |
register unsigned sum; |
| 353 |
|
| 354 |
tmp = col[RED]*NRED/256 - r; |
| 355 |
sum = tmp*tmp; |
| 356 |
tmp = col[GRN]*NGRN/256 - g; |
| 357 |
sum += tmp*tmp; |
| 358 |
tmp = col[BLU]*NBLU/256 - b; |
| 359 |
sum += tmp*tmp; |
| 360 |
return(sum); |
| 361 |
} |
| 362 |
|
| 363 |
|
| 364 |
static |
| 365 |
setclosest(nl, r, g, b) /* find index closest to color and assign */ |
| 366 |
BYTE *nl[]; |
| 367 |
int r, g, b; |
| 368 |
{ |
| 369 |
int ident; |
| 370 |
unsigned min; |
| 371 |
register unsigned d; |
| 372 |
register BYTE *p; |
| 373 |
/* get starting value */ |
| 374 |
min = dist(clrtab[ident=histo[r][g][b]], r, g, b); |
| 375 |
/* find minimum */ |
| 376 |
for (p = nl[ident]; *p != ident; p++) |
| 377 |
if ((d = dist(clrtab[*p], r, g, b)) < min) { |
| 378 |
min = d; |
| 379 |
histo[r][g][b] = *p; |
| 380 |
} |
| 381 |
} |
| 382 |
#endif |
