2 * Gif extracting routines - derived from libungif
4 * Portions Copyright 2006 Mike McCormack
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
22 * Original copyright notice:
24 * The GIFLIB distribution is Copyright (c) 1997 Eric S. Raymond
26 * Permission is hereby granted, free of charge, to any person obtaining a copy
27 * of this software and associated documentation files (the "Software"), to deal
28 * in the Software without restriction, including without limitation the rights
29 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
30 * copies of the Software, and to permit persons to whom the Software is
31 * furnished to do so, subject to the following conditions:
33 * The above copyright notice and this permission notice shall be included in
34 * all copies or substantial portions of the Software.
38 /******************************************************************************
39 * "Gif-Lib" - Yet another gif library.
41 * Written by: Gershon Elber IBM PC Ver 1.1, Aug. 1990
42 ******************************************************************************
43 * The kernel of the GIF Decoding process can be found here.
44 ******************************************************************************
46 * 16 Jun 89 - Version 1.0 by Gershon Elber.
47 * 3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names).
48 *****************************************************************************/
54 #define LZ_MAX_CODE 4095 /* Biggest code possible in 12 bits. */
57 #define NO_SUCH_CODE 4098 /* Impossible code, to signal empty. */
59 typedef struct GifFilePrivateType
{
60 GifWord BitsPerPixel
, /* Bits per pixel (Codes uses at least this + 1). */
61 ClearCode
, /* The CLEAR LZ code. */
62 EOFCode
, /* The EOF LZ code. */
63 RunningCode
, /* The next code algorithm can generate. */
64 RunningBits
, /* The number of bits required to represent RunningCode. */
65 MaxCode1
, /* 1 bigger than max. possible code, in RunningBits bits. */
66 LastCode
, /* The code before the current code. */
67 CrntCode
, /* Current algorithm code. */
68 StackPtr
, /* For character stack (see below). */
69 CrntShiftState
; /* Number of bits in CrntShiftDWord. */
70 unsigned long CrntShiftDWord
; /* For bytes decomposition into codes. */
71 unsigned long PixelCount
; /* Number of pixels in image. */
72 InputFunc Read
; /* function to read gif input (TVT) */
73 GifByteType Buf
[256]; /* Compressed input is buffered here. */
74 GifByteType Stack
[LZ_MAX_CODE
]; /* Decoded pixels are stacked here. */
75 GifByteType Suffix
[LZ_MAX_CODE
+ 1]; /* So we can trace the codes. */
76 GifPrefixType Prefix
[LZ_MAX_CODE
+ 1];
79 /* avoid extra function call in case we use fread (TVT) */
80 #define READ(_gif,_buf,_len) \
81 ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len)
83 static int DGifGetWord(GifFileType
*GifFile
, GifWord
*Word
);
84 static int DGifSetupDecompress(GifFileType
*GifFile
);
85 static int DGifDecompressLine(GifFileType
*GifFile
, GifPixelType
*Line
, int LineLen
);
86 static int DGifGetPrefixChar(GifPrefixType
*Prefix
, int Code
, int ClearCode
);
87 static int DGifDecompressInput(GifFileType
*GifFile
, int *Code
);
88 static int DGifBufferedInput(GifFileType
*GifFile
, GifByteType
*Buf
,
89 GifByteType
*NextByte
);
91 static int DGifGetExtensionNext(GifFileType
* GifFile
, GifByteType
** GifExtension
);
92 static int DGifGetCodeNext(GifFileType
* GifFile
, GifByteType
** GifCodeBlock
);
94 /******************************************************************************
95 * Miscellaneous utility functions
96 *****************************************************************************/
98 /* return smallest bitfield size n will fit in */
104 for (i
= 1; i
<= 8; i
++)
110 /******************************************************************************
111 * Color map object functions
112 *****************************************************************************/
115 * Allocate a color map of given size; initialize with contents of
116 * ColorMap if that pointer is non-NULL.
118 static ColorMapObject
*
119 MakeMapObject(int ColorCount
,
120 const GifColorType
* ColorMap
) {
122 ColorMapObject
*Object
;
124 /*** FIXME: Our ColorCount has to be a power of two. Is it necessary to
125 * make the user know that or should we automatically round up instead? */
126 if (ColorCount
!= (1 << BitSize(ColorCount
))) {
127 return ((ColorMapObject
*) NULL
);
130 Object
= malloc(sizeof(ColorMapObject
));
131 if (Object
== (ColorMapObject
*) NULL
) {
132 return ((ColorMapObject
*) NULL
);
135 Object
->Colors
= (GifColorType
*)calloc(ColorCount
, sizeof(GifColorType
));
136 if (Object
->Colors
== (GifColorType
*) NULL
) {
137 return ((ColorMapObject
*) NULL
);
140 Object
->ColorCount
= ColorCount
;
141 Object
->BitsPerPixel
= BitSize(ColorCount
);
144 memcpy(Object
->Colors
, ColorMap
, ColorCount
* sizeof(GifColorType
));
151 * Free a color map object
154 FreeMapObject(ColorMapObject
* Object
) {
156 if (Object
!= NULL
) {
157 free(Object
->Colors
);
160 * When we are willing to break API we need to make this function
161 * FreeMapObject(ColorMapObject **Object)
162 * and do this assignment to NULL here:
169 AddExtensionBlock(SavedImage
* New
,
171 unsigned char ExtData
[]) {
175 if (New
->ExtensionBlocks
== NULL
)
176 New
->ExtensionBlocks
= malloc(sizeof(ExtensionBlock
));
178 New
->ExtensionBlocks
= realloc(New
->ExtensionBlocks
,
179 sizeof(ExtensionBlock
) *
180 (New
->ExtensionBlockCount
+ 1));
182 if (New
->ExtensionBlocks
== NULL
)
185 ep
= &New
->ExtensionBlocks
[New
->ExtensionBlockCount
++];
188 ep
->Bytes
= malloc(ep
->ByteCount
);
189 if (ep
->Bytes
== NULL
)
193 memcpy(ep
->Bytes
, ExtData
, Len
);
194 ep
->Function
= New
->Function
;
201 FreeExtension(SavedImage
* Image
)
205 if ((Image
== NULL
) || (Image
->ExtensionBlocks
== NULL
)) {
208 for (ep
= Image
->ExtensionBlocks
;
209 ep
< (Image
->ExtensionBlocks
+ Image
->ExtensionBlockCount
); ep
++)
211 free(Image
->ExtensionBlocks
);
212 Image
->ExtensionBlocks
= NULL
;
215 /******************************************************************************
216 * Image block allocation functions
217 ******************************************************************************/
220 FreeSavedImages(GifFileType
* GifFile
) {
224 if ((GifFile
== NULL
) || (GifFile
->SavedImages
== NULL
)) {
227 for (sp
= GifFile
->SavedImages
;
228 sp
< GifFile
->SavedImages
+ GifFile
->ImageCount
; sp
++) {
229 if (sp
->ImageDesc
.ColorMap
) {
230 FreeMapObject(sp
->ImageDesc
.ColorMap
);
231 sp
->ImageDesc
.ColorMap
= NULL
;
234 free(sp
->RasterBits
);
236 if (sp
->ExtensionBlocks
)
239 free(GifFile
->SavedImages
);
240 GifFile
->SavedImages
=NULL
;
243 /******************************************************************************
244 * This routine should be called before any other DGif calls. Note that
245 * this routine is called automatically from DGif file open routines.
246 *****************************************************************************/
248 DGifGetScreenDesc(GifFileType
* GifFile
) {
253 /* Put the screen descriptor into the file: */
254 if (DGifGetWord(GifFile
, &GifFile
->SWidth
) == GIF_ERROR
||
255 DGifGetWord(GifFile
, &GifFile
->SHeight
) == GIF_ERROR
)
258 if (READ(GifFile
, Buf
, 3) != 3) {
261 GifFile
->SColorResolution
= (((Buf
[0] & 0x70) + 1) >> 4) + 1;
262 BitsPerPixel
= (Buf
[0] & 0x07) + 1;
263 GifFile
->SBackGroundColor
= Buf
[1];
264 if (Buf
[0] & 0x80) { /* Do we have global color map? */
266 GifFile
->SColorMap
= MakeMapObject(1 << BitsPerPixel
, NULL
);
267 if (GifFile
->SColorMap
== NULL
) {
271 /* Get the global color map: */
272 for (i
= 0; i
< GifFile
->SColorMap
->ColorCount
; i
++) {
273 if (READ(GifFile
, Buf
, 3) != 3) {
274 FreeMapObject(GifFile
->SColorMap
);
275 GifFile
->SColorMap
= NULL
;
278 GifFile
->SColorMap
->Colors
[i
].Red
= Buf
[0];
279 GifFile
->SColorMap
->Colors
[i
].Green
= Buf
[1];
280 GifFile
->SColorMap
->Colors
[i
].Blue
= Buf
[2];
283 GifFile
->SColorMap
= NULL
;
289 /******************************************************************************
290 * This routine should be called before any attempt to read an image.
291 *****************************************************************************/
293 DGifGetRecordType(GifFileType
* GifFile
,
294 GifRecordType
* Type
) {
298 if (READ(GifFile
, &Buf
, 1) != 1) {
304 *Type
= IMAGE_DESC_RECORD_TYPE
;
307 *Type
= EXTENSION_RECORD_TYPE
;
310 *Type
= TERMINATE_RECORD_TYPE
;
313 *Type
= UNDEFINED_RECORD_TYPE
;
320 /******************************************************************************
321 * This routine should be called before any attempt to read an image.
322 * Note it is assumed the Image desc. header (',') has been read.
323 *****************************************************************************/
325 DGifGetImageDesc(GifFileType
* GifFile
) {
329 GifFilePrivateType
*Private
= (GifFilePrivateType
*)GifFile
->Private
;
332 if (DGifGetWord(GifFile
, &GifFile
->Image
.Left
) == GIF_ERROR
||
333 DGifGetWord(GifFile
, &GifFile
->Image
.Top
) == GIF_ERROR
||
334 DGifGetWord(GifFile
, &GifFile
->Image
.Width
) == GIF_ERROR
||
335 DGifGetWord(GifFile
, &GifFile
->Image
.Height
) == GIF_ERROR
)
337 if (READ(GifFile
, Buf
, 1) != 1) {
340 BitsPerPixel
= (Buf
[0] & 0x07) + 1;
341 GifFile
->Image
.Interlace
= (Buf
[0] & 0x40);
342 if (Buf
[0] & 0x80) { /* Does this image have local color map? */
344 /*** FIXME: Why do we check both of these in order to do this?
345 * Why do we have both Image and SavedImages? */
346 if (GifFile
->Image
.ColorMap
&& GifFile
->SavedImages
== NULL
)
347 FreeMapObject(GifFile
->Image
.ColorMap
);
349 GifFile
->Image
.ColorMap
= MakeMapObject(1 << BitsPerPixel
, NULL
);
350 if (GifFile
->Image
.ColorMap
== NULL
) {
354 /* Get the image local color map: */
355 for (i
= 0; i
< GifFile
->Image
.ColorMap
->ColorCount
; i
++) {
356 if (READ(GifFile
, Buf
, 3) != 3) {
357 FreeMapObject(GifFile
->Image
.ColorMap
);
358 GifFile
->Image
.ColorMap
= NULL
;
361 GifFile
->Image
.ColorMap
->Colors
[i
].Red
= Buf
[0];
362 GifFile
->Image
.ColorMap
->Colors
[i
].Green
= Buf
[1];
363 GifFile
->Image
.ColorMap
->Colors
[i
].Blue
= Buf
[2];
365 } else if (GifFile
->Image
.ColorMap
) {
366 FreeMapObject(GifFile
->Image
.ColorMap
);
367 GifFile
->Image
.ColorMap
= NULL
;
370 if (GifFile
->SavedImages
) {
371 if ((GifFile
->SavedImages
= realloc(GifFile
->SavedImages
,
373 (GifFile
->ImageCount
+ 1))) == NULL
) {
377 if ((GifFile
->SavedImages
= malloc(sizeof(SavedImage
))) == NULL
) {
382 sp
= &GifFile
->SavedImages
[GifFile
->ImageCount
];
383 memcpy(&sp
->ImageDesc
, &GifFile
->Image
, sizeof(GifImageDesc
));
384 if (GifFile
->Image
.ColorMap
!= NULL
) {
385 sp
->ImageDesc
.ColorMap
= MakeMapObject(
386 GifFile
->Image
.ColorMap
->ColorCount
,
387 GifFile
->Image
.ColorMap
->Colors
);
388 if (sp
->ImageDesc
.ColorMap
== NULL
) {
392 sp
->RasterBits
= (unsigned char *)NULL
;
393 sp
->ExtensionBlockCount
= 0;
394 sp
->ExtensionBlocks
= (ExtensionBlock
*) NULL
;
396 GifFile
->ImageCount
++;
398 Private
->PixelCount
= (long)GifFile
->Image
.Width
*
399 (long)GifFile
->Image
.Height
;
401 DGifSetupDecompress(GifFile
); /* Reset decompress algorithm parameters. */
406 /******************************************************************************
407 * Get one full scanned line (Line) of length LineLen from GIF file.
408 *****************************************************************************/
410 DGifGetLine(GifFileType
* GifFile
,
415 GifFilePrivateType
*Private
= (GifFilePrivateType
*) GifFile
->Private
;
418 LineLen
= GifFile
->Image
.Width
;
420 if ((Private
->PixelCount
-= LineLen
) > 0xffff0000UL
) {
424 if (DGifDecompressLine(GifFile
, Line
, LineLen
) == GIF_OK
) {
425 if (Private
->PixelCount
== 0) {
426 /* We probably would not be called any more, so lets clean
427 * everything before we return: need to flush out all rest of
428 * image until empty block (size 0) detected. We use GetCodeNext. */
430 if (DGifGetCodeNext(GifFile
, &Dummy
) == GIF_ERROR
)
432 while (Dummy
!= NULL
) ;
439 /******************************************************************************
440 * Get an extension block (see GIF manual) from gif file. This routine only
441 * returns the first data block, and DGifGetExtensionNext should be called
442 * after this one until NULL extension is returned.
443 * The Extension should NOT be freed by the user (not dynamically allocated).
444 * Note it is assumed the Extension desc. header ('!') has been read.
445 *****************************************************************************/
447 DGifGetExtension(GifFileType
* GifFile
,
449 GifByteType
** Extension
) {
453 if (READ(GifFile
, &Buf
, 1) != 1) {
458 return DGifGetExtensionNext(GifFile
, Extension
);
461 /******************************************************************************
462 * Get a following extension block (see GIF manual) from gif file. This
463 * routine should be called until NULL Extension is returned.
464 * The Extension should NOT be freed by the user (not dynamically allocated).
465 *****************************************************************************/
467 DGifGetExtensionNext(GifFileType
* GifFile
,
468 GifByteType
** Extension
) {
471 GifFilePrivateType
*Private
= (GifFilePrivateType
*)GifFile
->Private
;
473 if (READ(GifFile
, &Buf
, 1) != 1) {
477 *Extension
= Private
->Buf
; /* Use private unused buffer. */
478 (*Extension
)[0] = Buf
; /* Pascal strings notation (pos. 0 is len.). */
479 if (READ(GifFile
, &((*Extension
)[1]), Buf
) != Buf
) {
488 /******************************************************************************
489 * Get 2 bytes (word) from the given file:
490 *****************************************************************************/
492 DGifGetWord(GifFileType
* GifFile
,
497 if (READ(GifFile
, c
, 2) != 2) {
501 *Word
= (((unsigned int)c
[1]) << 8) + c
[0];
505 /******************************************************************************
506 * Continue to get the image code in compressed form. This routine should be
507 * called until NULL block is returned.
508 * The block should NOT be freed by the user (not dynamically allocated).
509 *****************************************************************************/
511 DGifGetCodeNext(GifFileType
* GifFile
,
512 GifByteType
** CodeBlock
) {
515 GifFilePrivateType
*Private
= (GifFilePrivateType
*)GifFile
->Private
;
517 if (READ(GifFile
, &Buf
, 1) != 1) {
522 *CodeBlock
= Private
->Buf
; /* Use private unused buffer. */
523 (*CodeBlock
)[0] = Buf
; /* Pascal strings notation (pos. 0 is len.). */
524 if (READ(GifFile
, &((*CodeBlock
)[1]), Buf
) != Buf
) {
529 Private
->Buf
[0] = 0; /* Make sure the buffer is empty! */
530 Private
->PixelCount
= 0; /* And local info. indicate image read. */
536 /******************************************************************************
537 * Setup the LZ decompression for this image:
538 *****************************************************************************/
540 DGifSetupDecompress(GifFileType
* GifFile
) {
543 GifByteType CodeSize
;
544 GifPrefixType
*Prefix
;
545 GifFilePrivateType
*Private
= (GifFilePrivateType
*)GifFile
->Private
;
547 READ(GifFile
, &CodeSize
, 1); /* Read Code size from file. */
548 BitsPerPixel
= CodeSize
;
550 Private
->Buf
[0] = 0; /* Input Buffer empty. */
551 Private
->BitsPerPixel
= BitsPerPixel
;
552 Private
->ClearCode
= (1 << BitsPerPixel
);
553 Private
->EOFCode
= Private
->ClearCode
+ 1;
554 Private
->RunningCode
= Private
->EOFCode
+ 1;
555 Private
->RunningBits
= BitsPerPixel
+ 1; /* Number of bits per code. */
556 Private
->MaxCode1
= 1 << Private
->RunningBits
; /* Max. code + 1. */
557 Private
->StackPtr
= 0; /* No pixels on the pixel stack. */
558 Private
->LastCode
= NO_SUCH_CODE
;
559 Private
->CrntShiftState
= 0; /* No information in CrntShiftDWord. */
560 Private
->CrntShiftDWord
= 0;
562 Prefix
= Private
->Prefix
;
563 for (i
= 0; i
<= LZ_MAX_CODE
; i
++)
564 Prefix
[i
] = NO_SUCH_CODE
;
569 /******************************************************************************
570 * The LZ decompression routine:
571 * This version decompress the given gif file into Line of length LineLen.
572 * This routine can be called few times (one per scan line, for example), in
573 * order the complete the whole image.
574 *****************************************************************************/
576 DGifDecompressLine(GifFileType
* GifFile
,
581 int j
, CrntCode
, EOFCode
, ClearCode
, CrntPrefix
, LastCode
, StackPtr
;
582 GifByteType
*Stack
, *Suffix
;
583 GifPrefixType
*Prefix
;
584 GifFilePrivateType
*Private
= (GifFilePrivateType
*) GifFile
->Private
;
586 StackPtr
= Private
->StackPtr
;
587 Prefix
= Private
->Prefix
;
588 Suffix
= Private
->Suffix
;
589 Stack
= Private
->Stack
;
590 EOFCode
= Private
->EOFCode
;
591 ClearCode
= Private
->ClearCode
;
592 LastCode
= Private
->LastCode
;
595 /* Let pop the stack off before continueing to read the gif file: */
596 while (StackPtr
!= 0 && i
< LineLen
)
597 Line
[i
++] = Stack
[--StackPtr
];
600 while (i
< LineLen
) { /* Decode LineLen items. */
601 if (DGifDecompressInput(GifFile
, &CrntCode
) == GIF_ERROR
)
604 if (CrntCode
== EOFCode
) {
605 /* Note however that usually we will not be here as we will stop
606 * decoding as soon as we got all the pixel, or EOF code will
607 * not be read at all, and DGifGetLine/Pixel clean everything. */
608 if (i
!= LineLen
- 1 || Private
->PixelCount
!= 0) {
612 } else if (CrntCode
== ClearCode
) {
613 /* We need to start over again: */
614 for (j
= 0; j
<= LZ_MAX_CODE
; j
++)
615 Prefix
[j
] = NO_SUCH_CODE
;
616 Private
->RunningCode
= Private
->EOFCode
+ 1;
617 Private
->RunningBits
= Private
->BitsPerPixel
+ 1;
618 Private
->MaxCode1
= 1 << Private
->RunningBits
;
619 LastCode
= Private
->LastCode
= NO_SUCH_CODE
;
621 /* Its regular code - if in pixel range simply add it to output
622 * stream, otherwise trace to codes linked list until the prefix
623 * is in pixel range: */
624 if (CrntCode
< ClearCode
) {
625 /* This is simple - its pixel scalar, so add it to output: */
626 Line
[i
++] = CrntCode
;
628 /* Its a code to needed to be traced: trace the linked list
629 * until the prefix is a pixel, while pushing the suffix
630 * pixels on our stack. If we done, pop the stack in reverse
631 * (thats what stack is good for!) order to output. */
632 if (Prefix
[CrntCode
] == NO_SUCH_CODE
) {
633 /* Only allowed if CrntCode is exactly the running code:
634 * In that case CrntCode = XXXCode, CrntCode or the
635 * prefix code is last code and the suffix char is
636 * exactly the prefix of last code! */
637 if (CrntCode
== Private
->RunningCode
- 2) {
638 CrntPrefix
= LastCode
;
639 Suffix
[Private
->RunningCode
- 2] =
640 Stack
[StackPtr
++] = DGifGetPrefixChar(Prefix
,
647 CrntPrefix
= CrntCode
;
649 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
650 * during the trace. As we might loop forever, in case of
651 * defective image, we count the number of loops we trace
652 * and stop if we got LZ_MAX_CODE. Obviously we cannot
653 * loop more than that. */
655 while (j
++ <= LZ_MAX_CODE
&&
656 CrntPrefix
> ClearCode
&& CrntPrefix
<= LZ_MAX_CODE
) {
657 Stack
[StackPtr
++] = Suffix
[CrntPrefix
];
658 CrntPrefix
= Prefix
[CrntPrefix
];
660 if (j
>= LZ_MAX_CODE
|| CrntPrefix
> LZ_MAX_CODE
) {
663 /* Push the last character on stack: */
664 Stack
[StackPtr
++] = CrntPrefix
;
666 /* Now lets pop all the stack into output: */
667 while (StackPtr
!= 0 && i
< LineLen
)
668 Line
[i
++] = Stack
[--StackPtr
];
670 if (LastCode
!= NO_SUCH_CODE
) {
671 Prefix
[Private
->RunningCode
- 2] = LastCode
;
673 if (CrntCode
== Private
->RunningCode
- 2) {
674 /* Only allowed if CrntCode is exactly the running code:
675 * In that case CrntCode = XXXCode, CrntCode or the
676 * prefix code is last code and the suffix char is
677 * exactly the prefix of last code! */
678 Suffix
[Private
->RunningCode
- 2] =
679 DGifGetPrefixChar(Prefix
, LastCode
, ClearCode
);
681 Suffix
[Private
->RunningCode
- 2] =
682 DGifGetPrefixChar(Prefix
, CrntCode
, ClearCode
);
689 Private
->LastCode
= LastCode
;
690 Private
->StackPtr
= StackPtr
;
695 /******************************************************************************
696 * Routine to trace the Prefixes linked list until we get a prefix which is
697 * not code, but a pixel value (less than ClearCode). Returns that pixel value.
698 * If image is defective, we might loop here forever, so we limit the loops to
699 * the maximum possible if image O.k. - LZ_MAX_CODE times.
700 *****************************************************************************/
702 DGifGetPrefixChar(GifPrefixType
*Prefix
,
708 while (Code
> ClearCode
&& i
++ <= LZ_MAX_CODE
)
713 /******************************************************************************
714 * The LZ decompression input routine:
715 * This routine is responsible for the decompression of the bit stream from
716 * 8 bits (bytes) packets, into the real codes.
717 * Returns GIF_OK if read successfully.
718 *****************************************************************************/
720 DGifDecompressInput(GifFileType
* GifFile
,
723 GifFilePrivateType
*Private
= (GifFilePrivateType
*)GifFile
->Private
;
725 GifByteType NextByte
;
726 static unsigned short CodeMasks
[] = {
727 0x0000, 0x0001, 0x0003, 0x0007,
728 0x000f, 0x001f, 0x003f, 0x007f,
729 0x00ff, 0x01ff, 0x03ff, 0x07ff,
732 /* The image can't contain more than LZ_BITS per code. */
733 if (Private
->RunningBits
> LZ_BITS
) {
737 while (Private
->CrntShiftState
< Private
->RunningBits
) {
738 /* Needs to get more bytes from input stream for next code: */
739 if (DGifBufferedInput(GifFile
, Private
->Buf
, &NextByte
) == GIF_ERROR
) {
742 Private
->CrntShiftDWord
|=
743 ((unsigned long)NextByte
) << Private
->CrntShiftState
;
744 Private
->CrntShiftState
+= 8;
746 *Code
= Private
->CrntShiftDWord
& CodeMasks
[Private
->RunningBits
];
748 Private
->CrntShiftDWord
>>= Private
->RunningBits
;
749 Private
->CrntShiftState
-= Private
->RunningBits
;
751 /* If code cannot fit into RunningBits bits, must raise its size. Note
752 * however that codes above 4095 are used for special signaling.
753 * If we're using LZ_BITS bits already and we're at the max code, just
754 * keep using the table as it is, don't increment Private->RunningCode.
756 if (Private
->RunningCode
< LZ_MAX_CODE
+ 2 &&
757 ++Private
->RunningCode
> Private
->MaxCode1
&&
758 Private
->RunningBits
< LZ_BITS
) {
759 Private
->MaxCode1
<<= 1;
760 Private
->RunningBits
++;
765 /******************************************************************************
766 * This routines read one gif data block at a time and buffers it internally
767 * so that the decompression routine could access it.
768 * The routine returns the next byte from its internal buffer (or read next
769 * block in if buffer empty) and returns GIF_OK if successful.
770 *****************************************************************************/
772 DGifBufferedInput(GifFileType
* GifFile
,
774 GifByteType
* NextByte
) {
777 /* Needs to read the next buffer - this one is empty: */
778 if (READ(GifFile
, Buf
, 1) != 1) {
781 /* There shouldn't be any empty data blocks here as the LZW spec
782 * says the LZW termination code should come first. Therefore we
783 * shouldn't be inside this routine at that point.
788 if (READ(GifFile
, &Buf
[1], Buf
[0]) != Buf
[0]) {
792 Buf
[1] = 2; /* We use now the second place as last char read! */
795 *NextByte
= Buf
[Buf
[1]++];
802 /******************************************************************************
803 * This routine reads an entire GIF into core, hanging all its state info off
804 * the GifFileType pointer. Call DGifOpenFileName() or DGifOpenFileHandle()
805 * first to initialize I/O. Its inverse is EGifSpew().
806 ******************************************************************************/
808 DGifSlurp(GifFileType
* GifFile
) {
811 GifRecordType RecordType
;
813 GifByteType
*ExtData
;
814 SavedImage temp_save
;
816 temp_save
.ExtensionBlocks
= NULL
;
817 temp_save
.ExtensionBlockCount
= 0;
820 if (DGifGetRecordType(GifFile
, &RecordType
) == GIF_ERROR
)
823 switch (RecordType
) {
824 case IMAGE_DESC_RECORD_TYPE
:
825 if (DGifGetImageDesc(GifFile
) == GIF_ERROR
)
828 sp
= &GifFile
->SavedImages
[GifFile
->ImageCount
- 1];
829 ImageSize
= sp
->ImageDesc
.Width
* sp
->ImageDesc
.Height
;
831 sp
->RasterBits
= malloc(ImageSize
* sizeof(GifPixelType
));
832 if (sp
->RasterBits
== NULL
) {
835 if (DGifGetLine(GifFile
, sp
->RasterBits
, ImageSize
) ==
838 if (temp_save
.ExtensionBlocks
) {
839 sp
->ExtensionBlocks
= temp_save
.ExtensionBlocks
;
840 sp
->ExtensionBlockCount
= temp_save
.ExtensionBlockCount
;
842 temp_save
.ExtensionBlocks
= NULL
;
843 temp_save
.ExtensionBlockCount
= 0;
845 /* FIXME: The following is wrong. It is left in only for
846 * backwards compatibility. Someday it should go away. Use
847 * the sp->ExtensionBlocks->Function variable instead. */
848 sp
->Function
= sp
->ExtensionBlocks
[0].Function
;
852 case EXTENSION_RECORD_TYPE
:
853 if (DGifGetExtension(GifFile
, &temp_save
.Function
, &ExtData
) ==
856 while (ExtData
!= NULL
) {
858 /* Create an extension block with our data */
859 if (AddExtensionBlock(&temp_save
, ExtData
[0], &ExtData
[1])
863 if (DGifGetExtensionNext(GifFile
, &ExtData
) == GIF_ERROR
)
865 temp_save
.Function
= 0;
869 case TERMINATE_RECORD_TYPE
:
872 default: /* Should be trapped by DGifGetRecordType */
875 } while (RecordType
!= TERMINATE_RECORD_TYPE
);
877 /* Just in case the Gif has an extension block without an associated
878 * image... (Should we save this into a savefile structure with no image
879 * instead? Have to check if the present writing code can handle that as
881 if (temp_save
.ExtensionBlocks
)
882 FreeExtension(&temp_save
);
887 /******************************************************************************
888 * GifFileType constructor with user supplied input function (TVT)
889 *****************************************************************************/
891 DGifOpen(void *userData
,
892 InputFunc readFunc
) {
894 unsigned char Buf
[GIF_STAMP_LEN
+ 1];
895 GifFileType
*GifFile
;
896 GifFilePrivateType
*Private
;
898 GifFile
= malloc(sizeof(GifFileType
));
899 if (GifFile
== NULL
) {
903 memset(GifFile
, '\0', sizeof(GifFileType
));
905 Private
= malloc(sizeof(GifFilePrivateType
));
911 GifFile
->Private
= (void*)Private
;
913 Private
->Read
= readFunc
; /* TVT */
914 GifFile
->UserData
= userData
; /* TVT */
916 /* Lets see if this is a GIF file: */
917 if (READ(GifFile
, Buf
, GIF_STAMP_LEN
) != GIF_STAMP_LEN
) {
923 /* The GIF Version number is ignored at this time. Maybe we should do
924 * something more useful with it. */
925 Buf
[GIF_STAMP_LEN
] = 0;
926 if (memcmp(GIF_STAMP
, Buf
, GIF_VERSION_POS
) != 0) {
932 if (DGifGetScreenDesc(GifFile
) == GIF_ERROR
) {
941 /******************************************************************************
942 * This routine should be called last, to close the GIF file.
943 *****************************************************************************/
945 DGifCloseFile(GifFileType
* GifFile
) {
947 GifFilePrivateType
*Private
;
952 Private
= (GifFilePrivateType
*) GifFile
->Private
;
954 if (GifFile
->Image
.ColorMap
) {
955 FreeMapObject(GifFile
->Image
.ColorMap
);
956 GifFile
->Image
.ColorMap
= NULL
;
959 if (GifFile
->SColorMap
) {
960 FreeMapObject(GifFile
->SColorMap
);
961 GifFile
->SColorMap
= NULL
;
967 if (GifFile
->SavedImages
) {
968 FreeSavedImages(GifFile
);
969 GifFile
->SavedImages
= NULL
;