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110 lines
2.5 KiB
C
110 lines
2.5 KiB
C
/*
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* The Python Imaging Library.
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* $Id$
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*
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* Declarations for a fast, suspendable GIF decoder.
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*
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* Copyright (c) Fredrik Lundh 1995-96.
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*/
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/* Max size for a LZW code word. */
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#define GIFBITS 12
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#define GIFTABLE (1<<GIFBITS)
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#define GIFBUFFER (1<<GIFBITS)
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typedef struct {
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/* CONFIGURATION */
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/* Initial number of bits. The caller should clear all fields in
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this structure and set this field before calling the decoder
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the first time. */
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int bits;
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/* If set, this is an interlaced image. Process it the following way:
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* 1st pass: start at top line, lines are 8 pixels high, step 8 pixels
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* 2nd pass: start at line 4, lines are 4 pixels high, step 8 pixels
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* 3rd pass: start at line 2, lines are 2 pixels high, step 4 pixels
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* 4th pass: start at line 1, lines are 1 pixels high, step 2 pixels
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*/
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int interlace;
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/* PRIVATE CONTEXT (set by decoder) */
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/* Interlace parameters */
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int step, repeat;
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/* Input bit buffer */
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INT32 bitbuffer;
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int bitcount;
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int blocksize;
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/* Code buffer */
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int codesize;
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int codemask;
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/* Constant symbol codes */
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int clear, end;
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/* Symbol history */
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int lastcode;
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unsigned char lastdata;
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/* History buffer */
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int bufferindex;
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unsigned char buffer[GIFTABLE];
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/* Symbol table */
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unsigned INT16 link[GIFTABLE];
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unsigned char data[GIFTABLE];
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int next;
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} GIFDECODERSTATE;
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typedef struct GIFENCODERBLOCK_T
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{
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struct GIFENCODERBLOCK_T *next;
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int size;
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UINT8 data[255];
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} GIFENCODERBLOCK;
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typedef struct {
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/* CONFIGURATION */
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/* Initial number of bits. The caller should clear all fields in
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this structure and set this field before calling the encoder
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the first time. */
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int bits;
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/* NOTE: the expanding encoder ignores this field */
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/* If set, write an interlaced image (see above) */
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int interlace;
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/* PRIVATE CONTEXT (set by encoder) */
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/* Interlace parameters */
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int step, repeat;
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/* Output bit buffer */
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INT32 bitbuffer;
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int bitcount;
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/* Output buffer list (linked list) */
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GIFENCODERBLOCK* block; /* current block */
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GIFENCODERBLOCK* flush; /* output queue */
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GIFENCODERBLOCK* free; /* if not null, use this */
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/* Fields used for run-length encoding */
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int first; /* true if we haven't read the first pixel */
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int last; /* last byte value seen */
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int count; /* how many bytes with that value we've seen */
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int lastcode;
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} GIFENCODERSTATE;
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