1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.8 2002/03/09 19:42:47 jongfoster Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/deanimate.c,v $
6 * Purpose : Declares functions to deanimate GIF images on the fly.
8 * Functions declared include: gif_deanimate, buf_free,
9 * buf_copy, buf_getbyte, gif_skip_data_block, and
12 * Copyright : Written by and Copyright (C) 2001 by the the SourceForge
13 * IJBSWA team. http://ijbswa.sourceforge.net
15 * Based on the GIF file format specification (see
16 * http://tronche.com/computer-graphics/gif/gif89a.html)
17 * and ideas from the Image::DeAnim Perl module by
18 * Ken MacFarlane, <ksm+cpan@universal.dca.net>
20 * This program is free software; you can redistribute it
21 * and/or modify it under the terms of the GNU General
22 * Public License as published by the Free Software
23 * Foundation; either version 2 of the License, or (at
24 * your option) any later version.
26 * This program is distributed in the hope that it will
27 * be useful, but WITHOUT ANY WARRANTY; without even the
28 * implied warranty of MERCHANTABILITY or FITNESS FOR A
29 * PARTICULAR PURPOSE. See the GNU General Public
30 * License for more details.
32 * The GNU General Public License should be included with
33 * this file. If not, you can view it at
34 * http://www.gnu.org/copyleft/gpl.html
35 * or write to the Free Software Foundation, Inc., 59
36 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
39 * $Log: deanimate.c,v $
40 * Revision 1.8 2002/03/09 19:42:47 jongfoster
41 * Fixing more warnings
43 * Revision 1.7 2002/03/08 17:46:04 jongfoster
44 * Fixing int/size_t warnings
46 * Revision 1.6 2002/03/07 03:46:17 oes
47 * Fixed compiler warnings
49 * Revision 1.5 2001/09/10 10:16:06 oes
50 * Silenced compiler warnings
52 * Revision 1.4 2001/07/18 12:28:49 oes
53 * - Added feature for extracting the first frame
55 * - Separated image buffer extension into buf_extend
56 * - Extended gif deanimation to GIF87a (untested!)
59 * Revision 1.3 2001/07/15 13:57:50 jongfoster
60 * Adding #includes string.h and miscutil.h
62 * Revision 1.2 2001/07/13 13:46:20 oes
63 * Introduced GIF deanimation feature
66 **********************************************************************/
75 #include "deanimate.h"
78 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
80 /*********************************************************************
84 * Description : Safely frees a struct binbuffer
87 * 1 : buf = Pointer to the binbuffer to be freed
91 *********************************************************************/
92 void buf_free(struct binbuffer *buf)
94 if (buf == NULL) return;
96 if (buf->buffer != NULL)
106 /*********************************************************************
108 * Function : buf_extend
110 * Description : Ensure that a given binbuffer can hold a given amount
111 * of bytes, by reallocating its buffer if necessary.
112 * Allocate new mem in chunks of 1024 bytes, so we don't
113 * have to realloc() too often.
116 * 1 : buf = Pointer to the binbuffer
117 * 2 : length = Desired minimum size
120 * Returns : 0 on success, 1 on failiure.
122 *********************************************************************/
123 int buf_extend(struct binbuffer *buf, size_t length)
127 if (buf->offset + length > buf->size)
129 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
130 newbuf = (char *)realloc(buf->buffer, buf->size);
139 buf->buffer = newbuf;
148 /*********************************************************************
150 * Function : buf_copy
152 * Description : Safely copies a given amount of bytes from one
153 * struct binbuffer to another, advancing the
154 * offsets appropriately.
157 * 1 : src = Pointer to the source binbuffer
158 * 2 : dst = Pointer to the destination binbuffer
159 * 3 : length = Number of bytes to be copied
161 * Returns : 0 on success, 1 on failiure.
163 *********************************************************************/
164 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
168 * Sanity check: Can't copy more data than we have
170 if (src->offset + length > src->size)
176 * Ensure that dst can hold the new data
178 if (buf_extend(dst, length))
184 * Now that it's safe, memcpy() the desired amount of
185 * data from src to dst and adjust the offsets
187 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
188 src->offset += length;
189 dst->offset += length;
196 /*********************************************************************
198 * Function : buf_getbyte
200 * Description : Safely gets a byte from a given binbuffer at a
204 * 1 : buf = Pointer to the source binbuffer
205 * 2 : offset = Offset to the desired byte
207 * Returns : The byte on success, or 0 on failiure
209 *********************************************************************/
210 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
212 if (src->offset + offset < src->size)
214 return (unsigned char)*(src->buffer + src->offset + offset);
224 /*********************************************************************
226 * Function : gif_skip_data_block
228 * Description : Safely advances the offset of a given struct binbuffer
229 * that contains a GIF image and whose offset is
230 * positioned at the start of a data block, behind
234 * 1 : buf = Pointer to the binbuffer
236 * Returns : 0 on success, or 1 on failiure
238 *********************************************************************/
239 int gif_skip_data_block(struct binbuffer *buf)
244 * Data blocks are sequences of chunks, which are headed
245 * by a one-byte length field, with the last chunk having
248 while((c = buf_getbyte(buf, 0)) != '\0')
250 if ((buf->offset += c + 1) >= buf->size - 1)
262 /*********************************************************************
264 * Function : gif_extract_image
266 * Description : Safely extracts an image data block from a given
267 * struct binbuffer that contains a GIF image and whose
268 * offset is positioned at the start of a data block
269 * into a given destination binbuffer.
272 * 1 : src = Pointer to the source binbuffer
273 * 2 : dst = Pointer to the destination binbuffer
275 * Returns : 0 on success, or 1 on failiure
277 *********************************************************************/
278 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
283 * Remember the colormap flag and copy the image head
285 c = buf_getbyte(src, 9);
286 if (buf_copy(src, dst, 10))
292 * If the image has a local colormap, copy it.
296 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
301 if (buf_copy(src, dst, 1)) return 1;
304 * Copy the image chunk by chunk.
306 while((c = buf_getbyte(src, 0)) != '\0')
308 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
310 if (buf_copy(src, dst, 1)) return 1;
313 * Trim and rewind the dst buffer
315 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
316 dst->size = dst->offset;
323 /*********************************************************************
325 * Function : gif_deanimate
327 * Description : Deanimate a given GIF image, i.e. given a GIF with
328 * an (optional) image block and an arbitrary number
329 * of image extension blocks, produce an output GIF with
330 * only one image block that contains the last image
331 * (extenstion) block of the original.
332 * Also strip Comments, Application extenstions, etc.
335 * 1 : src = Pointer to the source binbuffer
336 * 2 : dst = Pointer to the destination binbuffer
337 * 3 : get_first_image = Flag: If set, get the first image
338 * If unset (default), get the last
340 * Returns : 0 on success, or 1 on failiure
342 *********************************************************************/
343 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
346 struct binbuffer *image;
348 if (NULL == src || NULL == dst)
353 c = buf_getbyte(src, 10);
356 * Check & copy GIF header
358 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
364 if (buf_copy(src, dst, 13))
371 * Look for global colormap and copy if found.
375 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
382 * Reserve a buffer for the current image block
384 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
390 * Parse the GIF block by block and copy the relevant
393 while(src->offset < src->size)
395 switch(buf_getbyte(src, 0))
398 * End-of-GIF Marker: Append current image and return
404 * Image block: Extract to current image buffer.
408 if (gif_extract_image(src, image)) goto failed;
409 if (get_first_image) goto write;
413 * Extension block: Look at next byte and decide
416 switch (buf_getbyte(src, 1))
419 * Image extension: Copy extension header and image
420 * to the current image buffer
424 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
425 if (gif_extract_image(src, image)) goto failed;
426 if (get_first_image) goto write;
430 * Application extension: Skip
433 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
437 * Comment extension: Skip
440 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
444 * Plain text extension: Skip
447 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
451 * Ooops, what type of extension is that?
459 * Ooops, what type of block is that?
465 } /* -END- while src */
468 * Either we got here by goto, or because the GIF is
469 * bogus and EOF was reached before an end-of-gif marker
478 * Append the current image to dst and return
482 if (buf_copy(image, dst, image->size)) goto failed;
483 if (buf_extend(dst, 1)) goto failed;
484 *(dst->buffer + dst->offset++) = 0x3b;