-
Notifications
You must be signed in to change notification settings - Fork 0
/
xv24to8.c
1754 lines (1443 loc) · 49.3 KB
/
xv24to8.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* xv24to8.c - contains the 24-to-8-bit Conv24to8() procedure
* and the 8-to-24-bit Conv8to24() procedure
*
* The Conv24to8 procedure takes a pointer to a 24-bit image (loaded
* previously). The image will be a w * h * 3 byte array of
* bytes. The image will be arranged with 3 bytes per pixel (in order
* R, G, and B), pixel 0 at the top left corner. (As normal.)
* The procedure also takes a maximum number of colors to use (numcols)
* and pointers to three 256-long arrays of bytes (to hold the returned
* colormap)
*
* Note that Conv24to8() does NOT free the pic24 image under any circumstances
*
* The Conv24to8 procedure will set up the following: it will allocate, make
* & return 'pic8', a 'w' by 'h' (passed in values) 8-bit picture.
* it will load up the rmap, gmap and bmap colormap arrays. it will NOT
* calculate numcols, since the cmap sort procedure has to be called anyway
*
* Conv24to8 returns 'pic8' if successful, 'NULL' on failure (presumably on a
* malloc())
*
* The 'slow' code, while still based on Heckbert's Median Cut algorithm,
* has been shamelessly lifted from the Independent JPEG Group's software
* (jquant2.c), as (for a variety of reasons) theirs was far better than
* the version I was previously using. Thanks guys!
*
* Also, as is my way, I've stripped out most of the IJG's well-written
* comments regarding their algorithm. Folks interested in learning how it
* works are encouraged to look at the original source. (jpeg/jquant2.c)
*
* contains:
* Cont24to8()
* Init24to8()
*/
#include "copyright.h"
/*
* Portions Copyright (C) 1989, 1991 by Jef Poskanzer. See copyright notice
* below, at the beginning of the relevant code.
*/
#include "xv.h"
static int quick_check PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
static int quick_quant PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
static int ppm_quant PARM((byte *,int,int, byte*, byte*,byte*,byte*,int));
static int slow_quant PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
/****************************/
void Init24to8()
{
/* doesn't do anything anymore... */
}
/****************************/
byte *Conv24to8(pic24,w,h,nc,rm,gm,bm)
byte *pic24;
byte *rm, *gm, *bm;
int w,h,nc;
{
/* returns pointer to new 8-bit-per-pixel image (w*h) if successful, or
NULL if unsuccessful */
int i;
byte *pic8;
if (!pic24) return NULL;
pic8 = (byte *) malloc((size_t) (w * h));
if (!pic8) {
fprintf(stderr,"%s: Conv24to8() - failed to allocate 'pic8'\n",cmd);
return pic8;
}
if (nc<=0) nc = 255; /* 'nc == 0' breaks code */
if (!noqcheck && quick_check(pic24, w,h, pic8, rm,gm,bm, nc)) {
SetISTR(ISTR_INFO,"No color compression was necessary.\n");
return pic8;
}
switch (conv24) {
case CONV24_FAST:
SetISTR(ISTR_INFO,"Doing 'quick' 24-bit to 8-bit conversion.");
i = quick_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
case CONV24_BEST:
SetISTR(ISTR_INFO,"Doing 'best' 24-bit to 8-bit conversion.");
i = ppm_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
case CONV24_SLOW:
default:
SetISTR(ISTR_INFO,"Doing 'slow' 24-bit to 8-bit conversion.");
i = slow_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
}
if (i) { free(pic8); pic8 = NULL; }
return pic8;
}
/***************************************************************/
byte *Conv8to24(pic8, w, h, rmap,gmap,bmap)
byte *pic8, *rmap, *gmap, *bmap;
int w, h;
{
/* converts an w*h 8-bit image (with colormap rmap,gmap,bmap) into a
* 24-bit image. Note, 'pic8' could be NULL
*
* returns pointer to new 24-bits-per-pixel image (w*h) if successful,
* or NULL if unsuccessful
*/
int i;
byte *pic24, *sp, *dp;
pic24 = (byte *) malloc((size_t) (w * h * 3));
if (!pic24) return pic24;
for (i=w*h, sp=pic8, dp=pic24; i; i--, sp++) {
if ((i&0x1ffff)==0) WaitCursor();
*dp++ = rmap[*sp];
*dp++ = gmap[*sp];
*dp++ = bmap[*sp];
}
return pic24;
}
/****************************/
static int quick_check(pic24, w,h, pic8, rmap,gmap,bmap, maxcol)
byte *pic24, *pic8, *rmap, *gmap, *bmap;
int w,h,maxcol;
{
/* scans picture until it finds more than 'maxcol' different colors. If it
finds more than 'maxcol' colors, it returns '0'. If it DOESN'T, it does
the 24-to-8 conversion by simply sticking the colors it found into
a colormap, and changing instances of a color in pic24 into colormap
indicies (in pic8) */
unsigned long colors[256],col;
int i, nc, low, high, mid;
byte *p, *pix;
if (maxcol>256) maxcol = 256;
/* put the first color in the table by hand */
nc = 0; mid = 0;
for (i=w*h,p=pic24; i; i--) {
col = (((u_long) *p++) << 16);
col += (((u_long) *p++) << 8);
col += *p++;
/* binary search the 'colors' array to see if it's in there */
low = 0; high = nc-1;
while (low <= high) {
mid = (low+high)/2;
if (col < colors[mid]) high = mid - 1;
else if (col > colors[mid]) low = mid + 1;
else break;
}
if (high < low) { /* didn't find color in list, add it. */
if (nc>=maxcol) return 0;
xvbcopy((char *) &colors[low], (char *) &colors[low+1],
(nc - low) * sizeof(u_long));
colors[low] = col;
nc++;
}
}
/* run through the data a second time, this time mapping pixel values in
pic24 into colormap offsets into 'colors' */
for (i=w*h,p=pic24, pix=pic8; i; i--,pix++) {
col = (((u_long) *p++) << 16);
col += (((u_long) *p++) << 8);
col += *p++;
/* binary search the 'colors' array. It *IS* in there */
low = 0; high = nc-1;
while (low <= high) {
mid = (low+high)/2;
if (col < colors[mid]) high = mid - 1;
else if (col > colors[mid]) low = mid + 1;
else break;
}
if (high < low) {
fprintf(stderr,"quick_check: impossible situation!\n");
exit(1);
}
*pix = mid;
}
/* and load up the 'desired colormap' */
for (i=0; i<nc; i++) {
rmap[i] = colors[i]>>16;
gmap[i] = (colors[i]>>8) & 0xff;
bmap[i] = colors[i] & 0xff;
}
return 1;
}
/************************************/
static int quick_quant(p24,w,h, p8, rmap,gmap,bmap, nc)
byte *p24, *p8, *rmap, *gmap, *bmap;
int w,h,nc;
{
/* called after 'pic8' has been alloced, pWIDE,pHIGH set up, mono/1-bit
checked already */
/* up to 256 colors: 3 bits R, 3 bits G, 2 bits B (RRRGGGBB) */
#define RMASK 0xe0
#define RSHIFT 0
#define GMASK 0xe0
#define GSHIFT 3
#define BMASK 0xc0
#define BSHIFT 6
byte *pp;
int r1, g1, b1;
int *thisline, *nextline, *thisptr, *nextptr, *tmpptr;
int i, j, val, pwide3;
int imax, jmax;
pp = p8; pwide3 = w * 3; imax = h-1; jmax = w-1;
/* load up colormap:
* note that 0 and 255 of each color are always in the map;
* intermediate values are evenly spaced.
*/
for (i=0; i<256; i++) {
rmap[i] = (((i<<RSHIFT) & RMASK) * 255 + RMASK/2) / RMASK;
gmap[i] = (((i<<GSHIFT) & GMASK) * 255 + GMASK/2) / GMASK;
bmap[i] = (((i<<BSHIFT) & BMASK) * 255 + BMASK/2) / BMASK;
}
thisline = (int *) malloc(pwide3 * sizeof(int));
nextline = (int *) malloc(pwide3 * sizeof(int));
if (!thisline || !nextline) {
if (thisline) free(thisline);
if (nextline) free(nextline);
fprintf(stderr,"%s: unable to allocate memory in quick_quant()\n", cmd);
return(1);
}
/* get first line of picture */
for (j=pwide3, tmpptr=nextline; j; j--) *tmpptr++ = (int) *p24++;
for (i=0; i<h; i++) {
tmpptr = thisline; thisline = nextline; nextline = tmpptr; /* swap */
if ((i&0x3f) == 0) WaitCursor();
if (i!=imax) /* get next line */
for (j=pwide3, tmpptr=nextline; j; j--)
*tmpptr++ = (int) *p24++;
for (j=0, thisptr=thisline, nextptr=nextline; j<w; j++,pp++) {
r1 = *thisptr++; g1 = *thisptr++; b1 = *thisptr++;
RANGE(r1,0,255); RANGE(g1,0,255); RANGE(b1,0,255);
/* choose actual pixel value */
val = (((r1&RMASK)>>RSHIFT) | ((g1&GMASK)>>GSHIFT) |
((b1&BMASK)>>BSHIFT));
*pp = val;
/* compute color errors */
r1 -= rmap[val];
g1 -= gmap[val];
b1 -= bmap[val];
/* Add fractions of errors to adjacent pixels */
if (j!=jmax) { /* adjust RIGHT pixel */
thisptr[0] += (r1*7) / 16;
thisptr[1] += (g1*7) / 16;
thisptr[2] += (b1*7) / 16;
}
if (i!=imax) { /* do BOTTOM pixel */
nextptr[0] += (r1*5) / 16;
nextptr[1] += (g1*5) / 16;
nextptr[2] += (b1*5) / 16;
if (j>0) { /* do BOTTOM LEFT pixel */
nextptr[-3] += (r1*3) / 16;
nextptr[-2] += (g1*3) / 16;
nextptr[-1] += (b1*3) / 16;
}
if (j!=jmax) { /* do BOTTOM RIGHT pixel */
nextptr[3] += (r1)/16;
nextptr[4] += (g1)/16;
nextptr[5] += (b1)/16;
}
nextptr += 3;
}
}
}
free(thisline);
free(nextline);
return 0;
#undef RMASK
#undef RSHIFT
#undef GMASK
#undef GSHIFT
#undef BMASK
#undef BSHIFT
}
/***************************************************************/
/* The following code based on code from the 'pbmplus' package */
/* written by Jef Poskanzer */
/***************************************************************/
/* ppmquant.c - quantize the colors in a pixmap down to a specified number
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
typedef unsigned char pixval;
#define PPM_MAXMAXVAL 255
typedef struct { pixval r, g, b; } pixel;
#define PPM_GETR(p) ((p).r)
#define PPM_GETG(p) ((p).g)
#define PPM_GETB(p) ((p).b)
#define PPM_ASSIGN(p,red,grn,blu) \
{ (p).r = (red); (p).g = (grn); (p).b = (blu); }
#define PPM_EQUAL(p,q) ( (p).r == (q).r && (p).g == (q).g && (p).b == (q).b )
/* Color scaling macro -- to make writing ppmtowhatever easier. */
#define PPM_DEPTH(newp,p,oldmaxval,newmaxval) \
PPM_ASSIGN( (newp), \
((int) PPM_GETR(p)) * ((int)newmaxval) / ((int)oldmaxval), \
((int) PPM_GETG(p)) * ((int)newmaxval) / ((int)oldmaxval), \
((int) PPM_GETB(p)) * ((int)newmaxval) / ((int)oldmaxval) )
/* Luminance macro. */
/*
* #define PPM_LUMIN(p) \
* ( 0.299 * PPM_GETR(p) + 0.587 * PPM_GETG(p) + 0.114 * PPM_GETB(p) )
*/
/* Luminance macro, using only integer ops. Returns an int (*256) JHB */
#define PPM_LUMIN(p) \
( 77 * PPM_GETR(p) + 150 * PPM_GETG(p) + 29 * PPM_GETB(p) )
/* Color histogram stuff. */
typedef struct chist_item* chist_vec;
struct chist_item { pixel color;
int value;
};
typedef struct chist_list_item* chist_list;
struct chist_list_item { struct chist_item ch;
chist_list next;
};
typedef chist_list* chash_table;
typedef struct box* box_vector;
struct box {
int index;
int colors;
int sum;
};
#define MAXCOLORS 32767
#define CLUSTER_MAXVAL 63
#define LARGE_LUM
#define REP_AVERAGE_PIXELS
#define FS_SCALE 1024
#define HASH_SIZE 6553
#define ppm_hashpixel(p) ((((int) PPM_GETR(p) * 33023 + \
(int) PPM_GETG(p) * 30013 + \
(int) PPM_GETB(p) * 27011) & 0x7fffffff) \
% HASH_SIZE)
/*** function defs ***/
static chist_vec mediancut PARM((chist_vec, int, int, int, int));
static int redcompare PARM((const void *, const void *));
static int greencompare PARM((const void *, const void *));
static int bluecompare PARM((const void *, const void *));
static int sumcompare PARM((const void *, const void *));
static chist_vec ppm_computechist PARM((pixel **, int,int,int,int *));
static chash_table ppm_computechash PARM((pixel **, int,int,int,int *));
static chist_vec ppm_chashtochist PARM((chash_table, int));
static chash_table ppm_allocchash PARM((void));
static void ppm_freechist PARM((chist_vec));
static void ppm_freechash PARM((chash_table));
/****************************************************************************/
static int ppm_quant(pic24, cols, rows, pic8, rmap, gmap, bmap, newcolors)
byte *pic24, *pic8, *rmap, *gmap, *bmap;
int cols, rows, newcolors;
{
pixel** pixels;
register pixel* pP;
int row;
register int col, limitcol;
pixval maxval, newmaxval;
int colors;
register int index;
chist_vec chv, colormap;
chash_table cht;
int i;
unsigned char *picptr;
static const char *fn = "ppmquant()";
index = 0;
maxval = 255;
/*
* reformat 24-bit pic24 image (3 bytes per pixel) into 2-dimensional
* array of pixel structures
*/
if (DEBUG) fprintf(stderr,"%s: remapping to ppm-style internal fmt\n", fn);
WaitCursor();
pixels = (pixel **) malloc(rows * sizeof(pixel *));
if (!pixels) FatalError("couldn't allocate 'pixels' array");
for (row=0; row<rows; row++) {
pixels[row] = (pixel *) malloc(cols * sizeof(pixel));
if (!pixels[row]) FatalError("couldn't allocate a row of pixels array");
for (col=0, pP=pixels[row]; col<cols; col++, pP++) {
pP->r = *pic24++;
pP->g = *pic24++;
pP->b = *pic24++;
}
}
if (DEBUG) fprintf(stderr,"%s: done format remapping\n", fn);
/*
* attempt to make a histogram of the colors, unclustered.
* If at first we don't succeed, lower maxval to increase color
* coherence and try again. This will eventually terminate, with
* maxval at worst 15, since 32^3 is approximately MAXCOLORS.
*/
WaitCursor();
for ( ; ; ) {
if (DEBUG) fprintf(stderr, "%s: making histogram\n", fn);
chv = ppm_computechist(pixels, cols, rows, MAXCOLORS, &colors);
if (chv != (chist_vec) 0) break;
if (DEBUG) fprintf(stderr, "%s: too many colors!\n", fn);
newmaxval = maxval / 2;
if (DEBUG) fprintf(stderr, "%s: rescaling colors (maxval=%d) %s\n",
fn, newmaxval, "to improve clustering");
for (row=0; row<rows; ++row)
for (col=0, pP=pixels[row]; col<cols; ++col, ++pP)
PPM_DEPTH( *pP, *pP, maxval, newmaxval );
maxval = newmaxval;
}
if (DEBUG) fprintf(stderr,"%s: %d colors found\n", fn, colors);
/*
* Step 3: apply median-cut to histogram, making the new colormap.
*/
WaitCursor();
if (DEBUG) fprintf(stderr, "%s: choosing %d colors\n", fn, newcolors);
colormap = mediancut(chv, colors, rows * cols, maxval, newcolors);
ppm_freechist(chv);
/*
* Step 4: map the colors in the image to their closest match in the
* new colormap, and write 'em out.
*/
if (DEBUG) fprintf(stderr,"%s: mapping image to new colors\n", fn);
cht = ppm_allocchash();
picptr = pic8;
for (row = 0; row < rows; ++row) {
col = 0; limitcol = cols; pP = pixels[row];
ProgressMeter(0, rows-1, row, "24 -> 8");
if ((row & 0x1f) == 0) WaitCursor();
do {
int hash;
chist_list chl;
/* Check hash table to see if we have already matched this color. */
hash = ppm_hashpixel(*pP);
for (chl = cht[hash]; chl; chl = chl->next)
if (PPM_EQUAL(chl->ch.color, *pP)) {index = chl->ch.value; break;}
if (!chl /*index = -1*/) {/* No; search colormap for closest match. */
register int i, r1, g1, b1, r2, g2, b2;
register long dist, newdist;
r1 = PPM_GETR( *pP );
g1 = PPM_GETG( *pP );
b1 = PPM_GETB( *pP );
dist = 2000000000;
for (i=0; i<newcolors; i++) {
r2 = PPM_GETR( colormap[i].color );
g2 = PPM_GETG( colormap[i].color );
b2 = PPM_GETB( colormap[i].color );
newdist = ( r1 - r2 ) * ( r1 - r2 ) +
( g1 - g2 ) * ( g1 - g2 ) +
( b1 - b2 ) * ( b1 - b2 );
if (newdist<dist) { index = i; dist = newdist; }
}
hash = ppm_hashpixel(*pP);
chl = (chist_list) malloc(sizeof(struct chist_list_item));
if (!chl) FatalError("ran out of memory adding to hash table");
chl->ch.color = *pP;
chl->ch.value = index;
chl->next = cht[hash];
cht[hash] = chl;
}
*picptr++ = index;
++col;
++pP;
}
while (col != limitcol);
}
/* rescale the colormap and load the XV colormap */
for (i=0; i<newcolors; i++) {
PPM_DEPTH(colormap[i].color, colormap[i].color, maxval, 255);
rmap[i] = PPM_GETR( colormap[i].color );
gmap[i] = PPM_GETG( colormap[i].color );
bmap[i] = PPM_GETB( colormap[i].color );
}
/* free the pixels array */
for (i=0; i<rows; i++) free(pixels[i]);
free(pixels);
/* free cht and colormap */
ppm_freechist(colormap);
ppm_freechash(cht);
return 0;
}
/*
** Here is the fun part, the median-cut colormap generator. This is based
** on Paul Heckbert's paper "Color Image Quantization for Frame Buffer
** Display", SIGGRAPH '82 Proceedings, page 297.
*/
/****************************************************************************/
static chist_vec mediancut( chv, colors, sum, maxval, newcolors )
chist_vec chv;
int colors, sum, newcolors;
int maxval;
{
chist_vec colormap;
box_vector bv;
register int bi, i;
int boxes;
bv = (box_vector) malloc(sizeof(struct box) * newcolors);
colormap = (chist_vec)
malloc(sizeof(struct chist_item) * newcolors );
if (!bv || !colormap) FatalError("unable to malloc in mediancut()");
for (i=0; i<newcolors; i++)
PPM_ASSIGN(colormap[i].color, 0, 0, 0);
/*
* Set up the initial box.
*/
bv[0].index = 0;
bv[0].colors = colors;
bv[0].sum = sum;
boxes = 1;
/*
** Main loop: split boxes until we have enough.
*/
while ( boxes < newcolors ) {
register int indx, clrs;
int sm;
register int minr, maxr, ming, maxg, minb, maxb, v;
int halfsum, lowersum;
/*
** Find the first splittable box.
*/
for (bi=0; bv[bi].colors<2 && bi<boxes; bi++) ;
if (bi == boxes) break; /* ran out of colors! */
indx = bv[bi].index;
clrs = bv[bi].colors;
sm = bv[bi].sum;
/*
** Go through the box finding the minimum and maximum of each
** component - the boundaries of the box.
*/
minr = maxr = PPM_GETR( chv[indx].color );
ming = maxg = PPM_GETG( chv[indx].color );
minb = maxb = PPM_GETB( chv[indx].color );
for (i=1; i<clrs; i++) {
v = PPM_GETR( chv[indx + i].color );
if (v < minr) minr = v;
if (v > maxr) maxr = v;
v = PPM_GETG( chv[indx + i].color );
if (v < ming) ming = v;
if (v > maxg) maxg = v;
v = PPM_GETB( chv[indx + i].color );
if (v < minb) minb = v;
if (v > maxb) maxb = v;
}
/*
** Find the largest dimension, and sort by that component. I have
** included two methods for determining the "largest" dimension;
** first by simply comparing the range in RGB space, and second
** by transforming into luminosities before the comparison. You
** can switch which method is used by switching the commenting on
** the LARGE_ defines at the beginning of this source file.
*/
{
/* LARGE_LUM version */
pixel p;
int rl, gl, bl;
PPM_ASSIGN(p, maxr - minr, 0, 0);
rl = PPM_LUMIN(p);
PPM_ASSIGN(p, 0, maxg - ming, 0);
gl = PPM_LUMIN(p);
PPM_ASSIGN(p, 0, 0, maxb - minb);
bl = PPM_LUMIN(p);
if (rl >= gl && rl >= bl)
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
redcompare );
else if (gl >= bl)
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
greencompare );
else
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
bluecompare );
}
/*
** Now find the median based on the counts, so that about half the
** pixels (not colors, pixels) are in each subdivision.
*/
lowersum = chv[indx].value;
halfsum = sm / 2;
for (i=1; i<clrs-1; i++) {
if (lowersum >= halfsum) break;
lowersum += chv[indx + i].value;
}
/*
** Split the box, and sort to bring the biggest boxes to the top.
*/
bv[bi].colors = i;
bv[bi].sum = lowersum;
bv[boxes].index = indx + i;
bv[boxes].colors = clrs - i;
bv[boxes].sum = sm - lowersum;
++boxes;
qsort((char*) bv, (size_t) boxes, sizeof(struct box), sumcompare);
} /* while (boxes ... */
/*
** Ok, we've got enough boxes. Now choose a representative color for
** each box. There are a number of possible ways to make this choice.
** One would be to choose the center of the box; this ignores any structure
** within the boxes. Another method would be to average all the colors in
** the box - this is the method specified in Heckbert's paper. A third
** method is to average all the pixels in the box. You can switch which
** method is used by switching the commenting on the REP_ defines at
** the beginning of this source file.
*/
for (bi=0; bi<boxes; bi++) {
/* REP_AVERAGE_PIXELS version */
register int indx = bv[bi].index;
register int clrs = bv[bi].colors;
register long r = 0, g = 0, b = 0, sum = 0;
for (i=0; i<clrs; i++) {
r += PPM_GETR( chv[indx + i].color ) * chv[indx + i].value;
g += PPM_GETG( chv[indx + i].color ) * chv[indx + i].value;
b += PPM_GETB( chv[indx + i].color ) * chv[indx + i].value;
sum += chv[indx + i].value;
}
r = r / sum; if (r>maxval) r = maxval; /* avoid math errors */
g = g / sum; if (g>maxval) g = maxval;
b = b / sum; if (b>maxval) b = maxval;
PPM_ASSIGN( colormap[bi].color, r, g, b );
}
free(bv);
return colormap;
}
/**********************************/
static int redcompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETR( ((chist_vec)p1)->color ) -
(int) PPM_GETR( ((chist_vec)p2)->color );
}
/**********************************/
static int greencompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETG( ((chist_vec)p1)->color ) -
(int) PPM_GETG( ((chist_vec)p2)->color );
}
/**********************************/
static int bluecompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETB( ((chist_vec)p1)->color ) -
(int) PPM_GETB( ((chist_vec)p2)->color );
}
/**********************************/
static int sumcompare(p1, p2)
const void *p1, *p2;
{
return ((box_vector) p2)->sum - ((box_vector) p1)->sum;
}
/****************************************************************************/
static chist_vec
ppm_computechist(pixels, cols, rows, maxcolors, colorsP)
pixel** pixels;
int cols, rows, maxcolors;
int* colorsP;
{
chash_table cht;
chist_vec chv;
cht = ppm_computechash(pixels, cols, rows, maxcolors, colorsP);
if (!cht) return (chist_vec) 0;
chv = ppm_chashtochist(cht, maxcolors);
ppm_freechash(cht);
return chv;
}
/****************************************************************************/
static chash_table ppm_computechash(pixels, cols, rows,
maxcolors, colorsP )
pixel** pixels;
int cols, rows, maxcolors;
int* colorsP;
{
chash_table cht;
register pixel* pP;
chist_list chl;
int col, row, hash;
cht = ppm_allocchash( );
*colorsP = 0;
/* Go through the entire image, building a hash table of colors. */
for (row=0; row<rows; row++)
for (col=0, pP=pixels[row]; col<cols; col++, pP++) {
hash = ppm_hashpixel(*pP);
for (chl = cht[hash]; chl != (chist_list) 0; chl = chl->next)
if (PPM_EQUAL(chl->ch.color, *pP)) break;
if (chl != (chist_list) 0) ++(chl->ch.value);
else {
if ((*colorsP)++ > maxcolors) {
ppm_freechash(cht);
return (chash_table) 0;
}
chl = (chist_list) malloc(sizeof(struct chist_list_item));
if (!chl) FatalError("ran out of memory computing hash table");
chl->ch.color = *pP;
chl->ch.value = 1;
chl->next = cht[hash];
cht[hash] = chl;
}
}
return cht;
}
/****************************************************************************/
static chash_table ppm_allocchash()
{
chash_table cht;
int i;
cht = (chash_table) malloc( HASH_SIZE * sizeof(chist_list) );
if (!cht) FatalError("ran out of memory allocating hash table");
for (i=0; i<HASH_SIZE; i++ )
cht[i] = (chist_list) 0;
return cht;
}
/****************************************************************************/
static chist_vec ppm_chashtochist( cht, maxcolors )
chash_table cht;
int maxcolors;
{
chist_vec chv;
chist_list chl;
int i, j;
/* Now collate the hash table into a simple chist array. */
chv = (chist_vec) malloc( maxcolors * sizeof(struct chist_item) );
/* (Leave room for expansion by caller.) */
if (!chv) FatalError("ran out of memory generating histogram");
/* Loop through the hash table. */
j = 0;
for (i=0; i<HASH_SIZE; i++)
for (chl = cht[i]; chl != (chist_list) 0; chl = chl->next) {
/* Add the new entry. */
chv[j] = chl->ch;
++j;
}
return chv;
}
/****************************************************************************/
static void ppm_freechist( chv )
chist_vec chv;
{
free( (char*) chv );
}
/****************************************************************************/
static void ppm_freechash( cht )
chash_table cht;
{
int i;
chist_list chl, chlnext;
for (i=0; i<HASH_SIZE; i++)
for (chl = cht[i]; chl != (chist_list) 0; chl = chlnext) {
chlnext = chl->next;
free( (char*) chl );
}
free( (char*) cht );
}
/***************************************************************/
/* The following is based on jquant2.c from version 5 */
/* of the IJG JPEG software, which is */
/* Copyright (C) 1991-1994, Thomas G. Lane. */
/***************************************************************/
#define MAXNUMCOLORS 256 /* maximum size of colormap */
#define C0_SCALE 2 /* scale R distances by this much */
#define C1_SCALE 3 /* scale G distances by this much */
#define C2_SCALE 1 /* and B by this much */
#define HIST_C0_BITS 5 /* bits of precision in R histogram */
#define HIST_C1_BITS 6 /* bits of precision in G histogram */
#define HIST_C2_BITS 5 /* bits of precision in B histogram */
/* Number of elements along histogram axes. */
#define HIST_C0_ELEMS (1<<HIST_C0_BITS)
#define HIST_C1_ELEMS (1<<HIST_C1_BITS)
#define HIST_C2_ELEMS (1<<HIST_C2_BITS)
/* These are the amounts to shift an input value to get a histogram index. */
#define C0_SHIFT (8-HIST_C0_BITS)
#define C1_SHIFT (8-HIST_C1_BITS)
#define C2_SHIFT (8-HIST_C2_BITS)
typedef unsigned char JSAMPLE;
typedef JSAMPLE * JSAMPROW;
typedef u_short histcell; /* histogram cell; prefer an unsigned type */
typedef histcell * histptr; /* for pointers to histogram cells */
typedef histcell hist1d[HIST_C2_ELEMS]; /* typedefs for the histogram array */
typedef hist1d hist2d[HIST_C1_ELEMS];
typedef hist2d hist3d[HIST_C0_ELEMS];
typedef short FSERROR; /* 16 bits should be enough */
typedef int LOCFSERROR; /* use 'int' for calculation temps */
typedef FSERROR *FSERRPTR; /* pointer to error array */