1 /*
2 * xvgifwr.c - handles writing of GIF files. based on flgife.c and
3 * flgifc.c from the FBM Library, by Michael Maudlin
4 *
5 * Contains:
6 * WriteGIF(fp, pic, ptype, w, h, rmap, gmap, bmap, numcols, colorstyle,
7 * comment)
8 *
9 * Note: slightly brain-damaged, in that it'll only write non-interlaced
10 * GIF files (in the interests of speed, or something)
11 *
12 */
13
14
15
16 /*****************************************************************
17 * Portions of this code Copyright (C) 1989 by Michael Mauldin.
18 * Permission is granted to use this file in whole or in
19 * part for any purpose, educational, recreational or commercial,
20 * provided that this copyright notice is retained unchanged.
21 * This software is available to all free of charge by anonymous
22 * FTP and in the UUNET archives.
23 *
24 *
25 * Authors: Michael Mauldin (mlm@cs.cmu.edu)
26 * David Rowley (mgardi@watdcsu.waterloo.edu)
27 *
28 * Based on: compress.c - File compression ala IEEE Computer, June 1984.
29 *
30 * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
31 * Jim McKie (decvax!mcvax!jim)
32 * Steve Davies (decvax!vax135!petsd!peora!srd)
33 * Ken Turkowski (decvax!decwrl!turtlevax!ken)
34 * James A. Woods (decvax!ihnp4!ames!jaw)
35 * Joe Orost (decvax!vax135!petsd!joe)
36 *****************************************************************/
37
38
39 #include "xv.h"
40
41 typedef long int count_int;
42
43 static int Width, Height;
44 static int curx, cury;
45 static long CountDown;
46 static int Interlace;
47
48 static void putword PARM((int, FILE *));
49 static void compress PARM((int, FILE *, byte *, int));
50 static void output PARM((int));
51 static void cl_block PARM((void));
52 static void cl_hash PARM((count_int));
53 static void char_init PARM((void));
54 static void char_out PARM((int));
55 static void flush_char PARM((void));
56
57
58 static byte pc2nc[256];
59
60
61 /*************************************************************/
WriteGIF(fp,pic,ptype,w,h,rmap,gmap,bmap,numcols,colorstyle,comment)62 int WriteGIF(fp, pic, ptype, w, h, rmap, gmap, bmap, numcols, colorstyle,
63 comment)
64 FILE *fp;
65 byte *pic;
66 int ptype, w,h;
67 byte *rmap, *gmap, *bmap;
68 int numcols, colorstyle;
69 char *comment;
70 {
71 int RWidth, RHeight;
72 int LeftOfs, TopOfs;
73 int ColorMapSize, InitCodeSize, Background, BitsPerPixel;
74 int i,j,nc;
75 byte *pic8;
76 byte rtemp[256],gtemp[256],btemp[256]; /* for 24-bit to 8-bit conversion */
77 byte r1[256],g1[256],b1[256]; /* for duplicated-color remapping */
78
79 if (ptype == PIC24) { /* have to quantize down to 8 bits */
80 pic8 = Conv24to8(pic, w, h, 256, rtemp,gtemp,btemp);
81 if (!pic8) FatalError("Unable to malloc in WriteGIF()");
82 rmap = rtemp; gmap = gtemp; bmap = btemp; numcols=256;
83 }
84 else pic8 = pic;
85
86
87
88 Interlace = 0;
89 Background = 0;
90
91
92 for (i=0; i<256; i++) { pc2nc[i] = r1[i] = g1[i] = b1[i] = 0; }
93
94 /* compute number of unique colors */
95 nc = 0;
96
97 for (i=0; i<numcols; i++) {
98 /* see if color #i is already used */
99 for (j=0; j<i; j++) {
100 if (rmap[i] == rmap[j] && gmap[i] == gmap[j] &&
101 bmap[i] == bmap[j]) break;
102 }
103
104 if (j==i) { /* wasn't found */
105 pc2nc[i] = nc;
106 r1[nc] = rmap[i];
107 g1[nc] = gmap[i];
108 b1[nc] = bmap[i];
109 nc++;
110 }
111 else pc2nc[i] = pc2nc[j];
112 }
113
114
115 /* figure out 'BitsPerPixel' */
116 for (i=1; i<8; i++)
117 if ( (1<<i) >= nc) break;
118
119 BitsPerPixel = i;
120
121 ColorMapSize = 1 << BitsPerPixel;
122
123 RWidth = Width = w;
124 RHeight = Height = h;
125 LeftOfs = TopOfs = 0;
126
127 CountDown = w * h; /* # of pixels we'll be doing */
128
129 if (BitsPerPixel <= 1) InitCodeSize = 2;
130 else InitCodeSize = BitsPerPixel;
131
132 curx = cury = 0;
133
134 if (!fp) {
135 fprintf(stderr, "WriteGIF: file not open for writing\n" );
136 if (ptype == PIC24) free(pic8);
137 return (1);
138 }
139
140 if (DEBUG)
141 fprintf(stderr,"WrGIF: pic=%lx, w,h=%dx%d, numcols=%d, Bits%d,Cmap=%d\n",
142 (u_long) pic8, w,h,numcols,BitsPerPixel,ColorMapSize);
143
144 if (comment && strlen(comment) > (size_t) 0)
145 fwrite("GIF89a", (size_t) 1, (size_t) 6, fp); /* the GIF magic number */
146 else
147 fwrite("GIF87a", (size_t) 1, (size_t) 6, fp); /* the GIF magic number */
148
149 putword(RWidth, fp); /* screen descriptor */
150 putword(RHeight, fp);
151
152 i = 0x80; /* Yes, there is a color map */
153 i |= (8-1)<<4; /* OR in the color resolution (hardwired 8) */
154 i |= (BitsPerPixel - 1); /* OR in the # of bits per pixel */
155 fputc(i,fp);
156
157 fputc(Background, fp); /* background color */
158
159 fputc(0, fp); /* future expansion byte */
160
161
162 if (colorstyle == 1) { /* greyscale */
163 for (i=0; i<ColorMapSize; i++) {
164 j = MONO(r1[i], g1[i], b1[i]);
165 fputc(j, fp);
166 fputc(j, fp);
167 fputc(j, fp);
168 }
169 }
170 else {
171 for (i=0; i<ColorMapSize; i++) { /* write out Global colormap */
172 fputc(r1[i], fp);
173 fputc(g1[i], fp);
174 fputc(b1[i], fp);
175 }
176 }
177
178 if (comment && strlen(comment) > (size_t) 0) { /* write comment blocks */
179 char *sp;
180 int i, blen;
181
182 fputc(0x21, fp); /* EXTENSION block */
183 fputc(0xFE, fp); /* comment extension */
184
185 sp = comment;
186 while ( (blen=strlen(sp)) > 0) {
187 if (blen>255) blen = 255;
188 fputc(blen, fp);
189 for (i=0; i<blen; i++, sp++) fputc(*sp, fp);
190 }
191 fputc(0, fp); /* zero-length data subblock to end extension */
192 }
193
194
195 fputc( ',', fp ); /* image separator */
196
197 /* Write the Image header */
198 putword(LeftOfs, fp);
199 putword(TopOfs, fp);
200 putword(Width, fp);
201 putword(Height, fp);
202 if (Interlace) fputc(0x40, fp); /* Use Global Colormap, maybe Interlace */
203 else fputc(0x00, fp);
204
205 fputc(InitCodeSize, fp);
206 compress(InitCodeSize+1, fp, pic8, w*h);
207
208 fputc(0,fp); /* Write out a Zero-length packet (EOF) */
209 fputc(';',fp); /* Write GIF file terminator */
210
211 if (ptype == PIC24) free(pic8);
212
213 if (ferror(fp)) return -1;
214 return (0);
215 }
216
217
218
219
220 /******************************/
putword(w,fp)221 static void putword(w, fp)
222 int w;
223 FILE *fp;
224 {
225 /* writes a 16-bit integer in GIF order (LSB first) */
226 fputc(w & 0xff, fp);
227 fputc((w>>8)&0xff, fp);
228 }
229
230
231
232
233 /***********************************************************************/
234
235
236 static unsigned long cur_accum = 0;
237 static int cur_bits = 0;
238
239
240
241
242 #define min(a,b) ((a>b) ? b : a)
243
244 #define XV_BITS 12 /* BITS was already defined on some systems */
245 #define MSDOS 1
246
247 #define HSIZE 5003 /* 80% occupancy */
248
249 typedef unsigned char char_type;
250
251
252 static int n_bits; /* number of bits/code */
253 static int maxbits = XV_BITS; /* user settable max # bits/code */
254 static int maxcode; /* maximum code, given n_bits */
255 static int maxmaxcode = 1 << XV_BITS; /* NEVER generate this */
256
257 #define MAXCODE(n_bits) ( (1 << (n_bits)) - 1)
258
259 static count_int htab [HSIZE];
260 static unsigned short codetab [HSIZE];
261 #define HashTabOf(i) htab[i]
262 #define CodeTabOf(i) codetab[i]
263
264 static int hsize = HSIZE; /* for dynamic table sizing */
265
266 /*
267 * To save much memory, we overlay the table used by compress() with those
268 * used by decompress(). The tab_prefix table is the same size and type
269 * as the codetab. The tab_suffix table needs 2**BITS characters. We
270 * get this from the beginning of htab. The output stack uses the rest
271 * of htab, and contains characters. There is plenty of room for any
272 * possible stack (stack used to be 8000 characters).
273 */
274
275 #define tab_prefixof(i) CodeTabOf(i)
276 #define tab_suffixof(i) ((char_type *)(htab))[i]
277 #define de_stack ((char_type *)&tab_suffixof(1<<XV_BITS))
278
279 static int free_ent = 0; /* first unused entry */
280
281 /*
282 * block compression parameters -- after all codes are used up,
283 * and compression rate changes, start over.
284 */
285 static int clear_flg = 0;
286
287 static long int in_count = 1; /* length of input */
288 static long int out_count = 0; /* # of codes output (for debugging) */
289
290 /*
291 * compress stdin to stdout
292 *
293 * Algorithm: use open addressing double hashing (no chaining) on the
294 * prefix code / next character combination. We do a variant of Knuth's
295 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
296 * secondary probe. Here, the modular division first probe is gives way
297 * to a faster exclusive-or manipulation. Also do block compression with
298 * an adaptive reset, whereby the code table is cleared when the compression
299 * ratio decreases, but after the table fills. The variable-length output
300 * codes are re-sized at this point, and a special CLEAR code is generated
301 * for the decompressor. Late addition: construct the table according to
302 * file size for noticeable speed improvement on small files. Please direct
303 * questions about this implementation to ames!jaw.
304 */
305
306 static int g_init_bits;
307 static FILE *g_outfile;
308
309 static int ClearCode;
310 static int EOFCode;
311
312
313 /********************************************************/
compress(init_bits,outfile,data,len)314 static void compress(init_bits, outfile, data, len)
315 int init_bits;
316 FILE *outfile;
317 byte *data;
318 int len;
319 {
320 register long fcode;
321 register int i = 0;
322 register int c;
323 register int ent;
324 register int disp;
325 register int hsize_reg;
326 register int hshift;
327
328 /*
329 * Set up the globals: g_init_bits - initial number of bits
330 * g_outfile - pointer to output file
331 */
332 g_init_bits = init_bits;
333 g_outfile = outfile;
334
335 /* initialize 'compress' globals */
336 maxbits = XV_BITS;
337 maxmaxcode = 1<<XV_BITS;
338 xvbzero((char *) htab, sizeof(htab));
339 xvbzero((char *) codetab, sizeof(codetab));
340 hsize = HSIZE;
341 free_ent = 0;
342 clear_flg = 0;
343 in_count = 1;
344 out_count = 0;
345 cur_accum = 0;
346 cur_bits = 0;
347
348
349 /*
350 * Set up the necessary values
351 */
352 out_count = 0;
353 clear_flg = 0;
354 in_count = 1;
355 maxcode = MAXCODE(n_bits = g_init_bits);
356
357 ClearCode = (1 << (init_bits - 1));
358 EOFCode = ClearCode + 1;
359 free_ent = ClearCode + 2;
360
361 char_init();
362 ent = pc2nc[*data++]; len--;
363
364 hshift = 0;
365 for ( fcode = (long) hsize; fcode < 65536L; fcode *= 2L )
366 hshift++;
367 hshift = 8 - hshift; /* set hash code range bound */
368
369 hsize_reg = hsize;
370 cl_hash( (count_int) hsize_reg); /* clear hash table */
371
372 output(ClearCode);
373
374 while (len) {
375 c = pc2nc[*data++]; len--;
376 in_count++;
377
378 fcode = (long) ( ( (long) c << maxbits) + ent);
379 i = (((int) c << hshift) ^ ent); /* xor hashing */
380
381 if ( HashTabOf (i) == fcode ) {
382 ent = CodeTabOf (i);
383 continue;
384 }
385
386 else if ( (long)HashTabOf (i) < 0 ) /* empty slot */
387 goto nomatch;
388
389 disp = hsize_reg - i; /* secondary hash (after G. Knott) */
390 if ( i == 0 )
391 disp = 1;
392
393 probe:
394 if ( (i -= disp) < 0 )
395 i += hsize_reg;
396
397 if ( HashTabOf (i) == fcode ) {
398 ent = CodeTabOf (i);
399 continue;
400 }
401
402 if ( (long)HashTabOf (i) >= 0 )
403 goto probe;
404
405 nomatch:
406 output(ent);
407 out_count++;
408 ent = c;
409
410 if ( free_ent < maxmaxcode ) {
411 CodeTabOf (i) = free_ent++; /* code -> hashtable */
412 HashTabOf (i) = fcode;
413 }
414 else
415 cl_block();
416 }
417
418 /* Put out the final code */
419 output(ent);
420 out_count++;
421 output(EOFCode);
422 }
423
424
425 /*****************************************************************
426 * TAG( output )
427 *
428 * Output the given code.
429 * Inputs:
430 * code: A n_bits-bit integer. If == -1, then EOF. This assumes
431 * that n_bits =< (long)wordsize - 1.
432 * Outputs:
433 * Outputs code to the file.
434 * Assumptions:
435 * Chars are 8 bits long.
436 * Algorithm:
437 * Maintain a BITS character long buffer (so that 8 codes will
438 * fit in it exactly). Use the VAX insv instruction to insert each
439 * code in turn. When the buffer fills up empty it and start over.
440 */
441
442 static
443 unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
444 0x001F, 0x003F, 0x007F, 0x00FF,
445 0x01FF, 0x03FF, 0x07FF, 0x0FFF,
446 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };
447
output(code)448 static void output(code)
449 int code;
450 {
451 cur_accum &= masks[cur_bits];
452
453 if (cur_bits > 0)
454 cur_accum |= ((long)code << cur_bits);
455 else
456 cur_accum = code;
457
458 cur_bits += n_bits;
459
460 while( cur_bits >= 8 ) {
461 char_out( (int) (cur_accum & 0xff) );
462 cur_accum >>= 8;
463 cur_bits -= 8;
464 }
465
466 /*
467 * If the next entry is going to be too big for the code size,
468 * then increase it, if possible.
469 */
470
471 if (free_ent > maxcode || clear_flg) {
472
473 if( clear_flg ) {
474 maxcode = MAXCODE (n_bits = g_init_bits);
475 clear_flg = 0;
476 }
477 else {
478 n_bits++;
479 if ( n_bits == maxbits )
480 maxcode = maxmaxcode;
481 else
482 maxcode = MAXCODE(n_bits);
483 }
484 }
485
486 if( code == EOFCode ) {
487 /* At EOF, write the rest of the buffer */
488 while( cur_bits > 0 ) {
489 char_out( (int)(cur_accum & 0xff) );
490 cur_accum >>= 8;
491 cur_bits -= 8;
492 }
493
494 flush_char();
495
496 fflush( g_outfile );
497
498 #ifdef FOO
499 if( ferror( g_outfile ) )
500 FatalError("unable to write GIF file");
501 #endif
502 }
503 }
504
505
506 /********************************/
cl_block()507 static void cl_block () /* table clear for block compress */
508 {
509 /* Clear out the hash table */
510
511 cl_hash ( (count_int) hsize );
512 free_ent = ClearCode + 2;
513 clear_flg = 1;
514
515 output(ClearCode);
516 }
517
518
519 /********************************/
cl_hash(hsize)520 static void cl_hash(hsize) /* reset code table */
521 register count_int hsize;
522 {
523 register count_int *htab_p = htab+hsize;
524 register long i;
525 register long m1 = -1;
526
527 i = hsize - 16;
528 do { /* might use Sys V memset(3) here */
529 *(htab_p-16) = m1;
530 *(htab_p-15) = m1;
531 *(htab_p-14) = m1;
532 *(htab_p-13) = m1;
533 *(htab_p-12) = m1;
534 *(htab_p-11) = m1;
535 *(htab_p-10) = m1;
536 *(htab_p-9) = m1;
537 *(htab_p-8) = m1;
538 *(htab_p-7) = m1;
539 *(htab_p-6) = m1;
540 *(htab_p-5) = m1;
541 *(htab_p-4) = m1;
542 *(htab_p-3) = m1;
543 *(htab_p-2) = m1;
544 *(htab_p-1) = m1;
545 htab_p -= 16;
546 } while ((i -= 16) >= 0);
547
548 for ( i += 16; i > 0; i-- )
549 *--htab_p = m1;
550 }
551
552
553 /******************************************************************************
554 *
555 * GIF Specific routines
556 *
557 ******************************************************************************/
558
559 /*
560 * Number of characters so far in this 'packet'
561 */
562 static int a_count;
563
564 /*
565 * Set up the 'byte output' routine
566 */
char_init()567 static void char_init()
568 {
569 a_count = 0;
570 }
571
572 /*
573 * Define the storage for the packet accumulator
574 */
575 static char accum[ 256 ];
576
577 /*
578 * Add a character to the end of the current packet, and if it is 254
579 * characters, flush the packet to disk.
580 */
char_out(c)581 static void char_out(c)
582 int c;
583 {
584 accum[ a_count++ ] = c;
585 if( a_count >= 254 )
586 flush_char();
587 }
588
589 /*
590 * Flush the packet to disk, and reset the accumulator
591 */
flush_char()592 static void flush_char()
593 {
594 if( a_count > 0 ) {
595 fputc(a_count, g_outfile );
596 fwrite(accum, (size_t) 1, (size_t) a_count, g_outfile );
597 a_count = 0;
598 }
599 }
600