1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.3 2001/07/15 13:57:50 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 1.3 2001/07/15 13:57:50 jongfoster
41 * Adding #includes string.h and miscutil.h
43 * Revision 1.2 2001/07/13 13:46:20 oes
44 * Introduced GIF deanimation feature
47 **********************************************************************/
56 #include "deanimate.h"
59 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
61 /*********************************************************************
65 * Description : Safely frees a struct binbuffer
68 * 1 : buf = Pointer to the binbuffer to be freed
72 *********************************************************************/
73 void buf_free(struct binbuffer *buf)
75 if (buf == NULL) return;
77 if (buf->buffer != NULL)
87 /*********************************************************************
89 * Function : buf_extend
91 * Description : Ensure that a given binbuffer can hold a given amount
92 * of bytes, by reallocating its buffer if necessary.
93 * Allocate new mem in chunks of 1000 bytes, so we don't
94 * have to realloc() too often.
97 * 1 : buf = Pointer to the binbuffer
98 * 2 : length = Desired minimum size
101 * Returns : 0 on success, 1 on failiure.
103 *********************************************************************/
104 int buf_extend(struct binbuffer *buf, int length)
108 if (buf->offset + length > buf->size)
110 buf->size = buf->size + length + 1000 - (buf->size + length) % 1000;
111 newbuf = (char *)realloc(buf->buffer, buf->size);
120 buf->buffer = newbuf;
129 /*********************************************************************
131 * Function : buf_copy
133 * Description : Safely copies a given amount of bytes from one
134 * struct binbuffer to another, advancing the
135 * offsets appropriately.
138 * 1 : src = Pointer to the source binbuffer
139 * 2 : dst = Pointer to the destination binbuffer
140 * 3 : length = Number of bytes to be copied
142 * Returns : 0 on success, 1 on failiure.
144 *********************************************************************/
145 int buf_copy(struct binbuffer *src, struct binbuffer *dst, int length)
149 * Sanity check: Can't copy more data than we have
151 if (src->offset + length > src->size)
157 * Ensure that dst can hold the new data
159 if (buf_extend(dst, length))
165 * Now that it's safe, memcpy() the desired amount of
166 * data from src to dst and adjust the offsets
168 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
169 src->offset += length;
170 dst->offset += length;
177 /*********************************************************************
179 * Function : buf_getbyte
181 * Description : Safely gets a byte from a given binbuffer at a
185 * 1 : buf = Pointer to the source binbuffer
186 * 2 : offset = Offset to the desired byte
188 * Returns : The byte on success, or 0 on failiure
190 *********************************************************************/
191 unsigned char buf_getbyte(struct binbuffer *src, int offset)
193 if (src->offset + offset < src->size)
195 return (unsigned char)*(src->buffer + src->offset + offset);
205 /*********************************************************************
207 * Function : gif_skip_data_block
209 * Description : Safely advances the offset of a given struct binbuffer
210 * that contains a GIF image and whose offset is
211 * positioned at the start of a data block, behind
215 * 1 : buf = Pointer to the binbuffer
217 * Returns : 0 on success, or 1 on failiure
219 *********************************************************************/
220 int gif_skip_data_block(struct binbuffer *buf)
225 * Data blocks are sequences of chunks, which are headed
226 * by a one-byte length field, with the last chunk having
229 while(c = buf_getbyte(buf, 0))
231 if ((buf->offset += c + 1) >= buf->size - 1)
243 /*********************************************************************
245 * Function : gif_extract_image
247 * Description : Safely extracts an image data block from a given
248 * struct binbuffer that contains a GIF image and whose
249 * offset is positioned at the start of a data block
250 * into a given destination binbuffer.
253 * 1 : src = Pointer to the source binbuffer
254 * 2 : dst = Pointer to the destination binbuffer
256 * Returns : 0 on success, or 1 on failiure
258 *********************************************************************/
259 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
264 * Remember the colormap flag and copy the image head
266 c = buf_getbyte(src, 9);
267 if (buf_copy(src, dst, 10))
273 * If the image has a local colormap, copy it.
277 if (buf_copy(src, dst, 3 * (1 << ((c & 0x07) + 1))))
282 if (buf_copy(src, dst, 1)) return 1;
285 * Copy the image chunk by chunk.
287 while(c = buf_getbyte(src, 0))
289 if (buf_copy(src, dst, c + 1)) return 1;
291 if (buf_copy(src, dst, 1)) return 1;
294 * Trim and rewind the dst buffer
296 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
297 dst->size = dst->offset;
304 /*********************************************************************
306 * Function : gif_deanimate
308 * Description : Deanimate a given GIF image, i.e. given a GIF with
309 * an (optional) image block and an arbitrary number
310 * of image extension blocks, produce an output GIF with
311 * only one image block that contains the last image
312 * (extenstion) block of the original.
313 * Also strip Comments, Application extenstions, etc.
316 * 1 : src = Pointer to the source binbuffer
317 * 2 : dst = Pointer to the destination binbuffer
318 * 3 : get_first_image = Flag: If set, get the first image
319 * If unset (default), get the last
321 * Returns : 0 on success, or 1 on failiure
323 *********************************************************************/
324 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
327 struct binbuffer *image;
329 if (NULL == src || NULL == dst)
334 c = buf_getbyte(src, 10);
337 * Check & copy GIF header
339 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
345 if (buf_copy(src, dst, 13))
352 * Look for global colormap and copy if found.
356 if (buf_copy(src, dst, 3 * (1 << ((c & 0x07) + 1))))
363 * Reserve a buffer for the current image block
365 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
371 * Parse the GIF block by block and copy the relevant
374 while(src->offset < src->size)
376 switch(buf_getbyte(src, 0))
379 * End-of-GIF Marker: Append current image and return
385 * Image block: Extract to current image buffer.
389 if (gif_extract_image(src, image)) goto failed;
390 if (get_first_image) goto write;
394 * Extension block: Look at next byte and decide
397 switch (buf_getbyte(src, 1))
400 * Image extension: Copy extension header and image
401 * to the current image buffer
405 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
406 if (gif_extract_image(src, image)) goto failed;
407 if (get_first_image) goto write;
411 * Application extension: Skip
414 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
418 * Comment extension: Skip
421 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
425 * Plain text extension: Skip
428 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
432 * Ooops, what type of extension is that?
440 * Ooops, what type of block is that?
446 } /* -END- while src */
449 * Either we got here by goto, or because the GIF is
450 * bogus and EOF was reached before an end-of-gif marker
459 * Append the current image to dst and return
463 if (buf_copy(image, dst, image->size)) goto failed;
464 if (buf_extend(dst, 1)) goto failed;
465 *(dst->buffer + dst->offset++) = 0x3b;