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108 lines
4.2 KiB
C
108 lines
4.2 KiB
C
/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef _GIF_H_
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#define _GIF_H_
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#define MAX_LZW_BITS 12
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#define MAX_BITS 4097 /* 2^MAX_LZW_BITS+1 */
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#define MAX_COLORS 256
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#define MIN_HOLD_SIZE 256
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enum { GIF_TRAILER = 0x3B }; //';'
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enum { GIF_IMAGE_SEPARATOR = 0x2C }; //','
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enum { GIF_EXTENSION_INTRODUCER = 0x21 }; //'!'
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enum { GIF_GRAPHIC_CONTROL_LABEL = 0xF9 };
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enum { GIF_COMMENT_LABEL = 0xFE };
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enum { GIF_PLAIN_TEXT_LABEL = 0x01 };
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enum { GIF_APPLICATION_EXTENSION_LABEL = 0xFF };
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/* gif2.h
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The interface for the GIF87/89a decoder.
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*/
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// List of possible parsing states
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typedef enum {
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gif_type,
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gif_global_header,
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gif_global_colormap,
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gif_image_start,
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gif_image_header,
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gif_image_header_continue,
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gif_image_colormap,
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gif_image_body,
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gif_lzw_start,
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gif_lzw,
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gif_sub_block,
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gif_extension,
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gif_control_extension,
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gif_consume_block,
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gif_skip_block,
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gif_done,
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gif_error,
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gif_comment_extension,
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gif_application_extension,
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gif_netscape_extension_block,
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gif_consume_netscape_extension,
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gif_consume_comment
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} gstate;
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/* A GIF decoder's state */
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typedef struct gif_struct {
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/* Parsing state machine */
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gstate state; /* Curent decoder master state */
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uint32_t bytes_to_consume; /* Number of bytes to accumulate */
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uint32_t bytes_in_hold; /* bytes accumulated so far*/
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/* LZW decoder state machine */
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uint8_t *stackp; /* Current stack pointer */
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int datasize;
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int codesize;
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int codemask;
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int avail; /* Index of next available slot in dictionary */
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int oldcode;
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uint8_t firstchar;
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int count; /* Remaining # bytes in sub-block */
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int bits; /* Number of unread bits in "datum" */
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int32_t datum; /* 32-bit input buffer */
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/* Output state machine */
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int ipass; /* Interlace pass; Ranges 1-4 if interlaced. */
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unsigned rows_remaining; /* Rows remaining to be output */
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unsigned irow; /* Current output row, starting at zero */
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uint8_t *rowp; /* Current output pointer */
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/* Parameters for image frame currently being decoded*/
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unsigned x_offset, y_offset; /* With respect to "screen" origin */
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unsigned height, width;
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int tpixel; /* Index of transparent pixel */
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int32_t disposal_method; /* Restore to background, leave in place, etc.*/
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uint32_t *local_colormap; /* Per-image colormap */
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int local_colormap_size; /* Size of local colormap array. */
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uint32_t delay_time; /* Display time, in milliseconds,
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for this image in a multi-image GIF */
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/* Global (multi-image) state */
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int version; /* Either 89 for GIF89 or 87 for GIF87 */
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unsigned screen_width; /* Logical screen width & height */
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unsigned screen_height;
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uint32_t global_colormap_depth; /* Depth of global colormap array. */
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int images_decoded; /* Counts images for multi-part GIFs */
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int loop_count; /* Netscape specific extension block to control
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the number of animation loops a GIF renders. */
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bool progressive_display; /* If TRUE, do Haeberli interlace hack */
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bool interlaced; /* TRUE, if scanlines arrive interlaced order */
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bool is_transparent; /* TRUE, if tpixel is valid */
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uint16_t prefix[MAX_BITS]; /* LZW decoding tables */
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uint8_t* hold; /* Accumulation buffer */
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uint32_t global_colormap[MAX_COLORS]; /* Default colormap if local not supplied */
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uint8_t suffix[MAX_BITS]; /* LZW decoding tables */
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uint8_t stack[MAX_BITS]; /* Base of LZW decoder stack */
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} gif_struct;
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#endif
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