obs/Source/libnsgif.h

/*
 * Copyright 2004 Richard Wilson <richard.wilson@netsurf-browser.org>
 * Copyright 2008 Sean Fox <dyntryx@gmail.com>
 *
 * This file is part of NetSurf's libnsgif, http://www.netsurf-browser.org/
 * Licenced under the MIT License,
 *                http://www.opensource.org/licenses/mit-license.php
 */

/** \file
 * Progressive animated GIF file decoding (interface).
 */

#ifndef _LIBNSGIF_H_
#define _LIBNSGIF_H_

typedef int BOOL;

#ifndef TRUE
#define TRUE 1
#define FALSE 0
#endif

//#include <stdbool.h>
#include "../extras/inttypes.h"

#if defined(__cplusplus)
extern "C"
{
#endif
/*    Error return values
*/
typedef enum {
    GIF_WORKING = 1,
    GIF_OK = 0,
    GIF_INSUFFICIENT_FRAME_DATA = -1,
    GIF_FRAME_DATA_ERROR = -2,
    GIF_INSUFFICIENT_DATA = -3,
    GIF_DATA_ERROR = -4,
    GIF_INSUFFICIENT_MEMORY = -5,
    GIF_FRAME_NO_DISPLAY = -6,
    GIF_END_OF_FRAME = -7
} gif_result;

/*    Maximum LZW bits available
*/
#define GIF_MAX_LZW 12

/*    The GIF frame data
*/
typedef struct gif_frame {
      BOOL display;                /**< whether the frame should be displayed/animated */
      unsigned int frame_delay;        /**< delay (in 100th second intervals) before animating the frame */
    /**    Internal members are listed below
    */
      unsigned int frame_pointer;        /**< offset (in bytes) to the GIF frame data */
      BOOL virgin;                /**< whether the frame has previously been used */
    BOOL opaque;                /**< whether the frame is totally opaque */
    BOOL redraw_required;            /**< whether a forcable screen redraw is required */
    unsigned char disposal_method;        /**< how the previous frame should be disposed; affects plotting */
    BOOL transparency;             /**< whether we acknoledge transparency */
    unsigned char transparency_index;    /**< the index designating a transparent pixel */
    unsigned int redraw_x;            /**< x co-ordinate of redraw rectangle */
    unsigned int redraw_y;            /**< y co-ordinate of redraw rectangle */
    unsigned int redraw_width;        /**< width of redraw rectangle */
    unsigned int redraw_height;        /**< height of redraw rectangle */
} gif_frame;

/*    API for Bitmap callbacks
*/
typedef void* (*gif_bitmap_cb_create)(int width, int height);
typedef void (*gif_bitmap_cb_destroy)(void *bitmap);
typedef unsigned char* (*gif_bitmap_cb_get_buffer)(void *bitmap);
typedef void (*gif_bitmap_cb_set_opaque)(void *bitmap, BOOL opaque);
typedef BOOL (*gif_bitmap_cb_test_opaque)(void *bitmap);
typedef void (*gif_bitmap_cb_modified)(void *bitmap);

/*    The Bitmap callbacks function table
*/
typedef struct gif_bitmap_callback_vt {
    gif_bitmap_cb_create bitmap_create;        /**< Create a bitmap. */
    gif_bitmap_cb_destroy bitmap_destroy;        /**< Free a bitmap. */
    gif_bitmap_cb_get_buffer bitmap_get_buffer;    /**< Return a pointer to the pixel data in a bitmap. */
    /**    Members below are optional
    */
    gif_bitmap_cb_set_opaque bitmap_set_opaque;    /**< Sets whether a bitmap should be plotted opaque. */
    gif_bitmap_cb_test_opaque bitmap_test_opaque;    /**< Tests whether a bitmap has an opaque alpha channel. */
    gif_bitmap_cb_modified bitmap_modified;    /**< The bitmap image has changed, so flush any persistant cache. */
} gif_bitmap_callback_vt;

/*    The GIF animation data
*/
typedef struct gif_animation {
    gif_bitmap_callback_vt bitmap_callbacks;    /**< callbacks for bitmap functions */
    unsigned char *gif_data;            /**< pointer to GIF data */
    unsigned int width;                /**< width of GIF (may increase during decoding) */
    unsigned int height;                /**< heigth of GIF (may increase during decoding) */
    unsigned int frame_count;            /**< number of frames decoded */
    unsigned int frame_count_partial;        /**< number of frames partially decoded */
    gif_frame *frames;                /**< decoded frames */
    int decoded_frame;                /**< current frame decoded to bitmap */
    void *frame_image;                /**< currently decoded image; stored as bitmap from bitmap_create callback */
    int loop_count;                    /**< number of times to loop animation */
    gif_result current_error;            /**< current error type, or 0 for none*/
    /**    Internal members are listed below
    */
    unsigned int buffer_position;            /**< current index into GIF data */
    unsigned int buffer_size;            /**< total number of bytes of GIF data available */
    unsigned int frame_holders;            /**< current number of frame holders */
    unsigned int background_index;            /**< index in the colour table for the background colour */
    unsigned int aspect_ratio;            /**< image aspect ratio (ignored) */
    unsigned int colour_table_size;        /**< size of colour table (in entries) */
    BOOL global_colours;                /**< whether the GIF has a global colour table */
    unsigned int *global_colour_table;        /**< global colour table */
    unsigned int *local_colour_table;        /**< local colour table */


    /*    General LZW values. They are NO LONGER shared for all GIFs being decoded BECAUSE
          THAT IS A TERRIBLE IDEA TO SAVE 10Kb or so per GIF.
    */
    unsigned char buf[4];
    unsigned char *direct;

    int table[2][(1 << GIF_MAX_LZW)];
    unsigned char stack[(1 << GIF_MAX_LZW) * 2];
    unsigned char *stack_pointer;
    int code_size, set_code_size;
    int max_code, max_code_size;
    int clear_code, end_code;
    int curbit, lastbit, last_byte;
    int firstcode, oldcode;
    BOOL zero_data_block;
    BOOL get_done;

    /*    Whether to clear the decoded image rather than plot
    */
    BOOL clear_image;
} gif_animation;

void gif_create(gif_animation *gif, gif_bitmap_callback_vt *bitmap_callbacks);
gif_result gif_initialise(gif_animation *gif, size_t size, unsigned char *data);
gif_result gif_decode_frame(gif_animation *gif, unsigned int frame);
void gif_finalise(gif_animation *gif);

#if defined(__cplusplus)
};
#endif

#endif