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/*
* Copyright 2004 Richard Wilson <richard.wilson@netsurf-browser.org>
* Copyright 2008 Sean Fox <dyntryx@gmail.com>
* Copyright 2013-2021 Michael Drake <tlsa@netsurf-browser.org>
*
* 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 NSNSGIF_H
#define NSNSGIF_H
#include <stdint.h>
#include <stdbool.h>
/* Error return values */
typedef enum {
NSGIF_WORKING = 1,
NSGIF_OK = 0,
NSGIF_INSUFFICIENT_DATA = -1,
NSGIF_INSUFFICIENT_FRAME_DATA = NSGIF_INSUFFICIENT_DATA,
NSGIF_FRAME_DATA_ERROR = -2,
NSGIF_DATA_ERROR = -4,
NSGIF_INSUFFICIENT_MEMORY = -5,
NSGIF_FRAME_NO_DISPLAY = -6,
NSGIF_END_OF_FRAME = -7
} nsgif_result;
/** GIF frame data */
typedef struct nsgif_frame {
/** whether the frame should be displayed/animated */
bool display;
/** delay (in cs) before animating the frame */
uint32_t frame_delay;
/* Internal members are listed below */
/** offset (in bytes) to the GIF frame data */
uint32_t frame_pointer;
/** whether the frame has previously been decoded. */
bool decoded;
/** whether the frame is totally opaque */
bool opaque;
/** whether a full image redraw is required */
bool redraw_required;
/** how the previous frame should be disposed; affects plotting */
uint8_t disposal_method;
/** whether we acknowledge transparency */
bool transparency;
/** the index designating a transparent pixel */
uint32_t transparency_index;
/** x co-ordinate of redraw rectangle */
uint32_t redraw_x;
/** y co-ordinate of redraw rectangle */
uint32_t redraw_y;
/** width of redraw rectangle */
uint32_t redraw_width;
/** height of redraw rectangle */
uint32_t redraw_height;
/* Frame flags */
uint32_t flags;
} nsgif_frame;
/* API for Bitmap callbacks */
typedef void* (*nsgif_bitmap_cb_create)(int width, int height);
typedef void (*nsgif_bitmap_cb_destroy)(void *bitmap);
typedef uint8_t* (*nsgif_bitmap_cb_get_buffer)(void *bitmap);
typedef void (*nsgif_bitmap_cb_set_opaque)(void *bitmap, bool opaque);
typedef bool (*nsgif_bitmap_cb_test_opaque)(void *bitmap);
typedef void (*nsgif_bitmap_cb_modified)(void *bitmap);
/** Bitmap callbacks function table */
typedef struct nsgif_bitmap_cb_vt {
/** Create a bitmap. */
nsgif_bitmap_cb_create create;
/** Free a bitmap. */
nsgif_bitmap_cb_destroy destroy;
/** Return a pointer to the pixel data in a bitmap. */
nsgif_bitmap_cb_get_buffer get_buffer;
/* Members below are optional */
/** Sets whether a bitmap should be plotted opaque. */
nsgif_bitmap_cb_set_opaque set_opaque;
/** Tests whether a bitmap has an opaque alpha channel. */
nsgif_bitmap_cb_test_opaque test_opaque;
/** The bitmap image has changed, so flush any persistent cache. */
nsgif_bitmap_cb_modified modified;
} nsgif_bitmap_cb_vt;
/** GIF animation data */
typedef struct nsgif_animation {
/** LZW decode context */
void *lzw_ctx;
/** callbacks for bitmap functions */
nsgif_bitmap_cb_vt bitmap;
/** pointer to GIF data */
const uint8_t *nsgif_data;
/** width of GIF (may increase during decoding) */
uint32_t width;
/** height of GIF (may increase during decoding) */
uint32_t height;
/** number of frames decoded */
uint32_t frame_count;
/** number of frames partially decoded */
uint32_t frame_count_partial;
/** decoded frames */
nsgif_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 */
uint32_t buffer_position;
/** total number of bytes of GIF data available */
uint32_t buffer_size;
/** current number of frame holders */
uint32_t frame_holders;
/** background index */
uint32_t bg_index;
/** background colour */
uint32_t bg_colour;
/** image aspect ratio (ignored) */
uint32_t aspect_ratio;
/** size of colour table (in entries) */
uint32_t colour_table_size;
/** whether the GIF has a global colour table */
bool global_colours;
/** global colour table */
uint32_t *global_colour_table;
/** local colour table */
uint32_t *local_colour_table;
/** current colour table */
uint32_t *colour_table;
/** previous frame for NSGIF_FRAME_RESTORE */
void *prev_frame;
/** previous frame index */
int prev_index;
/** previous frame width */
unsigned prev_width;
/** previous frame height */
unsigned prev_height;
} nsgif_animation;
/**
* Initialises necessary nsgif_animation members.
*/
void nsgif_create(nsgif_animation *gif, nsgif_bitmap_cb_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.
* - NSGIF_FRAME_DATA_ERROR for GIF frame data error
* - NSGIF_INSUFFICIENT_DATA reached unexpected end of source data
* - NSGIF_INSUFFICIENT_MEMORY for memory error
* - NSGIF_DATA_ERROR for GIF error
* - NSGIF_OK for successful decoding
* - NSGIF_WORKING for successful decoding if more frames are expected
*/
nsgif_result nsgif_initialise(nsgif_animation *gif, size_t size, const uint8_t *data);
/**
* Decodes a GIF frame.
*
* \return Error return value.
* - NSGIF_FRAME_DATA_ERROR for GIF frame data error
* - NSGIF_DATA_ERROR for GIF error (invalid frame header)
* - NSGIF_INSUFFICIENT_DATA reached unexpected end of source data
* - NSGIF_INSUFFICIENT_MEMORY for insufficient memory to process
* - NSGIF_OK for successful decoding
*/
nsgif_result nsgif_decode_frame(nsgif_animation *gif, uint32_t frame);
/**
* Releases any workspace held by a gif
*/
void nsgif_finalise(nsgif_animation *gif);
#endif
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