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