1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.7 2002/03/08 17:46:04 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 1.7 2002/03/08 17:46:04 jongfoster
41 * Fixing int/size_t warnings
43 * Revision 1.6 2002/03/07 03:46:17 oes
44 * Fixed compiler warnings
46 * Revision 1.5 2001/09/10 10:16:06 oes
47 * Silenced compiler warnings
49 * Revision 1.4 2001/07/18 12:28:49 oes
50 * - Added feature for extracting the first frame
52 * - Separated image buffer extension into buf_extend
53 * - Extended gif deanimation to GIF87a (untested!)
56 * Revision 1.3 2001/07/15 13:57:50 jongfoster
57 * Adding #includes string.h and miscutil.h
59 * Revision 1.2 2001/07/13 13:46:20 oes
60 * Introduced GIF deanimation feature
63 **********************************************************************/
72 #include "deanimate.h"
75 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
77 /*********************************************************************
81 * Description : Safely frees a struct binbuffer
84 * 1 : buf = Pointer to the binbuffer to be freed
88 *********************************************************************/
89 void buf_free(struct binbuffer *buf)
91 if (buf == NULL) return;
93 if (buf->buffer != NULL)
103 /*********************************************************************
105 * Function : buf_extend
107 * Description : Ensure that a given binbuffer can hold a given amount
108 * of bytes, by reallocating its buffer if necessary.
109 * Allocate new mem in chunks of 1024 bytes, so we don't
110 * have to realloc() too often.
113 * 1 : buf = Pointer to the binbuffer
114 * 2 : length = Desired minimum size
117 * Returns : 0 on success, 1 on failiure.
119 *********************************************************************/
120 int buf_extend(struct binbuffer *buf, size_t length)
124 if (buf->offset + length > buf->size)
126 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
127 newbuf = (char *)realloc(buf->buffer, buf->size);
136 buf->buffer = newbuf;
145 /*********************************************************************
147 * Function : buf_copy
149 * Description : Safely copies a given amount of bytes from one
150 * struct binbuffer to another, advancing the
151 * offsets appropriately.
154 * 1 : src = Pointer to the source binbuffer
155 * 2 : dst = Pointer to the destination binbuffer
156 * 3 : length = Number of bytes to be copied
158 * Returns : 0 on success, 1 on failiure.
160 *********************************************************************/
161 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
165 * Sanity check: Can't copy more data than we have
167 if (src->offset + length > src->size)
173 * Ensure that dst can hold the new data
175 if (buf_extend(dst, length))
181 * Now that it's safe, memcpy() the desired amount of
182 * data from src to dst and adjust the offsets
184 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
185 src->offset += length;
186 dst->offset += length;
193 /*********************************************************************
195 * Function : buf_getbyte
197 * Description : Safely gets a byte from a given binbuffer at a
201 * 1 : buf = Pointer to the source binbuffer
202 * 2 : offset = Offset to the desired byte
204 * Returns : The byte on success, or 0 on failiure
206 *********************************************************************/
207 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
209 if (src->offset + offset < src->size)
211 return (unsigned char)*(src->buffer + src->offset + offset);
221 /*********************************************************************
223 * Function : gif_skip_data_block
225 * Description : Safely advances the offset of a given struct binbuffer
226 * that contains a GIF image and whose offset is
227 * positioned at the start of a data block, behind
231 * 1 : buf = Pointer to the binbuffer
233 * Returns : 0 on success, or 1 on failiure
235 *********************************************************************/
236 int gif_skip_data_block(struct binbuffer *buf)
241 * Data blocks are sequences of chunks, which are headed
242 * by a one-byte length field, with the last chunk having
245 while((c = buf_getbyte(buf, 0)))
247 if ((buf->offset += c + 1) >= buf->size - 1)
259 /*********************************************************************
261 * Function : gif_extract_image
263 * Description : Safely extracts an image data block from a given
264 * struct binbuffer that contains a GIF image and whose
265 * offset is positioned at the start of a data block
266 * into a given destination binbuffer.
269 * 1 : src = Pointer to the source binbuffer
270 * 2 : dst = Pointer to the destination binbuffer
272 * Returns : 0 on success, or 1 on failiure
274 *********************************************************************/
275 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
280 * Remember the colormap flag and copy the image head
282 c = buf_getbyte(src, 9);
283 if (buf_copy(src, dst, 10))
289 * If the image has a local colormap, copy it.
293 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
298 if (buf_copy(src, dst, 1)) return 1;
301 * Copy the image chunk by chunk.
303 while((c = buf_getbyte(src, 0)))
305 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
307 if (buf_copy(src, dst, 1)) return 1;
310 * Trim and rewind the dst buffer
312 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
313 dst->size = dst->offset;
320 /*********************************************************************
322 * Function : gif_deanimate
324 * Description : Deanimate a given GIF image, i.e. given a GIF with
325 * an (optional) image block and an arbitrary number
326 * of image extension blocks, produce an output GIF with
327 * only one image block that contains the last image
328 * (extenstion) block of the original.
329 * Also strip Comments, Application extenstions, etc.
332 * 1 : src = Pointer to the source binbuffer
333 * 2 : dst = Pointer to the destination binbuffer
334 * 3 : get_first_image = Flag: If set, get the first image
335 * If unset (default), get the last
337 * Returns : 0 on success, or 1 on failiure
339 *********************************************************************/
340 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
343 struct binbuffer *image;
345 if (NULL == src || NULL == dst)
350 c = buf_getbyte(src, 10);
353 * Check & copy GIF header
355 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
361 if (buf_copy(src, dst, 13))
368 * Look for global colormap and copy if found.
372 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
379 * Reserve a buffer for the current image block
381 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
387 * Parse the GIF block by block and copy the relevant
390 while(src->offset < src->size)
392 switch(buf_getbyte(src, 0))
395 * End-of-GIF Marker: Append current image and return
401 * Image block: Extract to current image buffer.
405 if (gif_extract_image(src, image)) goto failed;
406 if (get_first_image) goto write;
410 * Extension block: Look at next byte and decide
413 switch (buf_getbyte(src, 1))
416 * Image extension: Copy extension header and image
417 * to the current image buffer
421 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
422 if (gif_extract_image(src, image)) goto failed;
423 if (get_first_image) goto write;
427 * Application extension: Skip
430 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
434 * Comment extension: Skip
437 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
441 * Plain text extension: Skip
444 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
448 * Ooops, what type of extension is that?
456 * Ooops, what type of block is that?
462 } /* -END- while src */
465 * Either we got here by goto, or because the GIF is
466 * bogus and EOF was reached before an end-of-gif marker
475 * Append the current image to dst and return
479 if (buf_copy(image, dst, image->size)) goto failed;
480 if (buf_extend(dst, 1)) goto failed;
481 *(dst->buffer + dst->offset++) = 0x3b;