1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.6 2002/03/07 03:46:17 oes 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 1.6 2002/03/07 03:46:17 oes
41 * Fixed compiler warnings
43 * Revision 1.5 2001/09/10 10:16:06 oes
44 * Silenced compiler warnings
46 * Revision 1.4 2001/07/18 12:28:49 oes
47 * - Added feature for extracting the first frame
49 * - Separated image buffer extension into buf_extend
50 * - Extended gif deanimation to GIF87a (untested!)
53 * Revision 1.3 2001/07/15 13:57:50 jongfoster
54 * Adding #includes string.h and miscutil.h
56 * Revision 1.2 2001/07/13 13:46:20 oes
57 * Introduced GIF deanimation feature
60 **********************************************************************/
69 #include "deanimate.h"
72 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
74 /*********************************************************************
78 * Description : Safely frees a struct binbuffer
81 * 1 : buf = Pointer to the binbuffer to be freed
85 *********************************************************************/
86 void buf_free(struct binbuffer *buf)
88 if (buf == NULL) return;
90 if (buf->buffer != NULL)
100 /*********************************************************************
102 * Function : buf_extend
104 * Description : Ensure that a given binbuffer can hold a given amount
105 * of bytes, by reallocating its buffer if necessary.
106 * Allocate new mem in chunks of 1024 bytes, so we don't
107 * have to realloc() too often.
110 * 1 : buf = Pointer to the binbuffer
111 * 2 : length = Desired minimum size
114 * Returns : 0 on success, 1 on failiure.
116 *********************************************************************/
117 int buf_extend(struct binbuffer *buf, size_t length)
121 if (buf->offset + length > buf->size)
123 buf->size = ((buf->size + length + 1023) & ~1023);
124 newbuf = (char *)realloc(buf->buffer, buf->size);
133 buf->buffer = newbuf;
142 /*********************************************************************
144 * Function : buf_copy
146 * Description : Safely copies a given amount of bytes from one
147 * struct binbuffer to another, advancing the
148 * offsets appropriately.
151 * 1 : src = Pointer to the source binbuffer
152 * 2 : dst = Pointer to the destination binbuffer
153 * 3 : length = Number of bytes to be copied
155 * Returns : 0 on success, 1 on failiure.
157 *********************************************************************/
158 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
162 * Sanity check: Can't copy more data than we have
164 if (src->offset + length > src->size)
170 * Ensure that dst can hold the new data
172 if (buf_extend(dst, length))
178 * Now that it's safe, memcpy() the desired amount of
179 * data from src to dst and adjust the offsets
181 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
182 src->offset += length;
183 dst->offset += length;
190 /*********************************************************************
192 * Function : buf_getbyte
194 * Description : Safely gets a byte from a given binbuffer at a
198 * 1 : buf = Pointer to the source binbuffer
199 * 2 : offset = Offset to the desired byte
201 * Returns : The byte on success, or 0 on failiure
203 *********************************************************************/
204 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
206 if (src->offset + offset < src->size)
208 return (unsigned char)*(src->buffer + src->offset + offset);
218 /*********************************************************************
220 * Function : gif_skip_data_block
222 * Description : Safely advances the offset of a given struct binbuffer
223 * that contains a GIF image and whose offset is
224 * positioned at the start of a data block, behind
228 * 1 : buf = Pointer to the binbuffer
230 * Returns : 0 on success, or 1 on failiure
232 *********************************************************************/
233 int gif_skip_data_block(struct binbuffer *buf)
238 * Data blocks are sequences of chunks, which are headed
239 * by a one-byte length field, with the last chunk having
242 while((c = buf_getbyte(buf, 0)))
244 if ((buf->offset += c + 1) >= buf->size - 1)
256 /*********************************************************************
258 * Function : gif_extract_image
260 * Description : Safely extracts an image data block from a given
261 * struct binbuffer that contains a GIF image and whose
262 * offset is positioned at the start of a data block
263 * into a given destination binbuffer.
266 * 1 : src = Pointer to the source binbuffer
267 * 2 : dst = Pointer to the destination binbuffer
269 * Returns : 0 on success, or 1 on failiure
271 *********************************************************************/
272 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
277 * Remember the colormap flag and copy the image head
279 c = buf_getbyte(src, 9);
280 if (buf_copy(src, dst, 10))
286 * If the image has a local colormap, copy it.
290 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
295 if (buf_copy(src, dst, 1)) return 1;
298 * Copy the image chunk by chunk.
300 while((c = buf_getbyte(src, 0)))
302 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
304 if (buf_copy(src, dst, 1)) return 1;
307 * Trim and rewind the dst buffer
309 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
310 dst->size = dst->offset;
317 /*********************************************************************
319 * Function : gif_deanimate
321 * Description : Deanimate a given GIF image, i.e. given a GIF with
322 * an (optional) image block and an arbitrary number
323 * of image extension blocks, produce an output GIF with
324 * only one image block that contains the last image
325 * (extenstion) block of the original.
326 * Also strip Comments, Application extenstions, etc.
329 * 1 : src = Pointer to the source binbuffer
330 * 2 : dst = Pointer to the destination binbuffer
331 * 3 : get_first_image = Flag: If set, get the first image
332 * If unset (default), get the last
334 * Returns : 0 on success, or 1 on failiure
336 *********************************************************************/
337 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
340 struct binbuffer *image;
342 if (NULL == src || NULL == dst)
347 c = buf_getbyte(src, 10);
350 * Check & copy GIF header
352 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
358 if (buf_copy(src, dst, 13))
365 * Look for global colormap and copy if found.
369 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
376 * Reserve a buffer for the current image block
378 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
384 * Parse the GIF block by block and copy the relevant
387 while(src->offset < src->size)
389 switch(buf_getbyte(src, 0))
392 * End-of-GIF Marker: Append current image and return
398 * Image block: Extract to current image buffer.
402 if (gif_extract_image(src, image)) goto failed;
403 if (get_first_image) goto write;
407 * Extension block: Look at next byte and decide
410 switch (buf_getbyte(src, 1))
413 * Image extension: Copy extension header and image
414 * to the current image buffer
418 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
419 if (gif_extract_image(src, image)) goto failed;
420 if (get_first_image) goto write;
424 * Application extension: Skip
427 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
431 * Comment extension: Skip
434 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
438 * Plain text extension: Skip
441 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
445 * Ooops, what type of extension is that?
453 * Ooops, what type of block is that?
459 } /* -END- while src */
462 * Either we got here by goto, or because the GIF is
463 * bogus and EOF was reached before an end-of-gif marker
472 * Append the current image to dst and return
476 if (buf_copy(image, dst, image->size)) goto failed;
477 if (buf_extend(dst, 1)) goto failed;
478 *(dst->buffer + dst->offset++) = 0x3b;