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/*
* 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
* Interface to progressive animated GIF file decoding.
*/
#ifndef _LIBNSGIF_H_
#define _LIBNSGIF_H_
#include <stdbool.h>
#include <inttypes.h>
/* 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;
/** GIF frame data */
typedef struct gif_frame {
/** whether the frame should be displayed/animated */
bool display;
/** delay (in cs) before animating the frame */
unsigned int frame_delay;
/* Internal members are listed below */
/** offset (in bytes) to the GIF frame data */
unsigned int frame_pointer;
/** whether the frame has previously been used */
bool virgin;
/** whether the frame is totally opaque */
bool opaque;
/** whether a forcable screen redraw is required */
bool redraw_required;
/** how the previous frame should be disposed; affects plotting */
unsigned char disposal_method;
/** whether we acknoledge transparency */
bool transparency;
/** the index designating a transparent pixel */
unsigned int transparency_index;
/** x co-ordinate of redraw rectangle */
unsigned int redraw_x;
/** y co-ordinate of redraw rectangle */
unsigned int redraw_y;
/** width of redraw rectangle */
unsigned int redraw_width;
/** height of redraw rectangle */
unsigned int redraw_height;
/* Frame flags */
unsigned int flags;
} 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);
/** Bitmap callbacks function table */
typedef struct gif_bitmap_callback_vt {
/** Create a bitmap. */
gif_bitmap_cb_create bitmap_create;
/** Free a bitmap. */
gif_bitmap_cb_destroy bitmap_destroy;
/** Return a pointer to the pixel data in a bitmap. */
gif_bitmap_cb_get_buffer bitmap_get_buffer;
/* Members below are optional */
/** Sets whether a bitmap should be plotted opaque. */
gif_bitmap_cb_set_opaque bitmap_set_opaque;
/** Tests whether a bitmap has an opaque alpha channel. */
gif_bitmap_cb_test_opaque bitmap_test_opaque;
/** The bitmap image has changed, so flush any persistant cache. */
gif_bitmap_cb_modified bitmap_modified;
} gif_bitmap_callback_vt;
/** GIF animation data */
typedef struct gif_animation {
/** LZW decode context */
void *lzw_ctx;
/** callbacks for bitmap functions */
gif_bitmap_callback_vt bitmap_callbacks;
/** pointer to GIF data */
unsigned char *gif_data;
/** width of GIF (may increase during decoding) */
unsigned int width;
/** heigth of GIF (may increase during decoding) */
unsigned int height;
/** number of frames decoded */
unsigned int frame_count;
/** number of frames partially decoded */
unsigned int frame_count_partial;
/** decoded frames */
gif_frame *frames;
/** current frame decoded to bitmap */
int decoded_frame;
/** currently decoded image; stored as bitmap from bitmap_create callback */
void *frame_image;
/** number of times to loop animation */
int loop_count;
/* Internal members are listed below */
/** current index into GIF data */
unsigned int buffer_position;
/** total number of bytes of GIF data available */
unsigned int buffer_size;
/** current number of frame holders */
unsigned int frame_holders;
/** background index */
unsigned int bg_index;
/** background colour */
unsigned int bg_colour;
/** image aspect ratio (ignored) */
unsigned int aspect_ratio;
/** size of colour table (in entries) */
unsigned int colour_table_size;
/** whether the GIF has a global colour table */
bool global_colours;
/** global colour table */
unsigned int *global_colour_table;
/** local colour table */
unsigned int *local_colour_table;
/** current colour table */
unsigned int *colour_table;
/** previous frame for GIF_FRAME_RESTORE */
void *prev_frame;
/** previous frame index */
int prev_index;
/** previous frame width */
unsigned prev_width;
/** previous frame height */
unsigned prev_height;
} gif_animation;
/**
* Initialises necessary gif_animation members.
*/
void gif_create(gif_animation *gif, gif_bitmap_callback_vt *bitmap_callbacks);
/**
* Initialises any workspace held by the animation and attempts to decode
* any information that hasn't already been decoded.
* If an error occurs, all previously decoded frames are retained.
*
* @return Error return value.
* - GIF_FRAME_DATA_ERROR for GIF frame data error
* - GIF_INSUFFICIENT_FRAME_DATA for insufficient data to process
* any more frames
* - GIF_INSUFFICIENT_MEMORY for memory error
* - GIF_DATA_ERROR for GIF error
* - GIF_INSUFFICIENT_DATA for insufficient data to do anything
* - GIF_OK for successful decoding
* - GIF_WORKING for successful decoding if more frames are expected
*/
gif_result gif_initialise(gif_animation *gif, size_t size, unsigned char *data);
/**
* Decodes a GIF frame.
*
* @return Error return value. If a frame does not contain any image data,
* GIF_OK is returned and gif->current_error is set to
* GIF_FRAME_NO_DISPLAY
* - GIF_FRAME_DATA_ERROR for GIF frame data error
* - GIF_INSUFFICIENT_FRAME_DATA for insufficient data to complete the frame
* - GIF_DATA_ERROR for GIF error (invalid frame header)
* - GIF_INSUFFICIENT_DATA for insufficient data to do anything
* - GIF_INSUFFICIENT_MEMORY for insufficient memory to process
* - GIF_OK for successful decoding
*/
gif_result gif_decode_frame(gif_animation *gif, unsigned int frame);
/**
* Releases any workspace held by a gif
*/
void gif_finalise(gif_animation *gif);
#endif
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