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225 lines
9.4 KiB
C
225 lines
9.4 KiB
C
// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Demux API.
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// Enables extraction of image and extended format data from WebP files.
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// Code Example: Demuxing WebP data to extract all the frames, ICC profile
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// and EXIF/XMP metadata.
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/*
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WebPDemuxer* demux = WebPDemux(&webp_data);
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uint32_t width = WebPDemuxGetI(demux, WEBP_FF_CANVAS_WIDTH);
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uint32_t height = WebPDemuxGetI(demux, WEBP_FF_CANVAS_HEIGHT);
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// ... (Get information about the features present in the WebP file).
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uint32_t flags = WebPDemuxGetI(demux, WEBP_FF_FORMAT_FLAGS);
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// ... (Iterate over all frames).
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WebPIterator iter;
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if (WebPDemuxGetFrame(demux, 1, &iter)) {
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do {
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// ... (Consume 'iter'; e.g. Decode 'iter.fragment' with WebPDecode(),
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// ... and get other frame properties like width, height, offsets etc.
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// ... see 'struct WebPIterator' below for more info).
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} while (WebPDemuxNextFrame(&iter));
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WebPDemuxReleaseIterator(&iter);
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}
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// ... (Extract metadata).
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WebPChunkIterator chunk_iter;
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if (flags & ICCP_FLAG) WebPDemuxGetChunk(demux, "ICCP", 1, &chunk_iter);
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// ... (Consume the ICC profile in 'chunk_iter.chunk').
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WebPDemuxReleaseChunkIterator(&chunk_iter);
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if (flags & EXIF_FLAG) WebPDemuxGetChunk(demux, "EXIF", 1, &chunk_iter);
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// ... (Consume the EXIF metadata in 'chunk_iter.chunk').
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WebPDemuxReleaseChunkIterator(&chunk_iter);
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if (flags & XMP_FLAG) WebPDemuxGetChunk(demux, "XMP ", 1, &chunk_iter);
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// ... (Consume the XMP metadata in 'chunk_iter.chunk').
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WebPDemuxReleaseChunkIterator(&chunk_iter);
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WebPDemuxDelete(demux);
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*/
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#ifndef WEBP_WEBP_DEMUX_H_
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#define WEBP_WEBP_DEMUX_H_
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#include "./mux_types.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define WEBP_DEMUX_ABI_VERSION 0x0101 // MAJOR(8b) + MINOR(8b)
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// Note: forward declaring enumerations is not allowed in (strict) C and C++,
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// the types are left here for reference.
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// typedef enum WebPDemuxState WebPDemuxState;
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// typedef enum WebPFormatFeature WebPFormatFeature;
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typedef struct WebPDemuxer WebPDemuxer;
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typedef struct WebPIterator WebPIterator;
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typedef struct WebPChunkIterator WebPChunkIterator;
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//------------------------------------------------------------------------------
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// Returns the version number of the demux library, packed in hexadecimal using
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// 8bits for each of major/minor/revision. E.g: v2.5.7 is 0x020507.
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WEBP_EXTERN(int) WebPGetDemuxVersion(void);
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//------------------------------------------------------------------------------
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// Life of a Demux object
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typedef enum WebPDemuxState {
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WEBP_DEMUX_PARSE_ERROR = -1, // An error occurred while parsing.
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WEBP_DEMUX_PARSING_HEADER = 0, // Not enough data to parse full header.
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WEBP_DEMUX_PARSED_HEADER = 1, // Header parsing complete,
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// data may be available.
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WEBP_DEMUX_DONE = 2 // Entire file has been parsed.
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} WebPDemuxState;
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// Internal, version-checked, entry point
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WEBP_EXTERN(WebPDemuxer*) WebPDemuxInternal(
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const WebPData*, int, WebPDemuxState*, int);
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// Parses the full WebP file given by 'data'.
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// Returns a WebPDemuxer object on successful parse, NULL otherwise.
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static WEBP_INLINE WebPDemuxer* WebPDemux(const WebPData* data) {
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return WebPDemuxInternal(data, 0, NULL, WEBP_DEMUX_ABI_VERSION);
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}
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// Parses the possibly incomplete WebP file given by 'data'.
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// If 'state' is non-NULL it will be set to indicate the status of the demuxer.
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// Returns NULL in case of error or if there isn't enough data to start parsing;
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// and a WebPDemuxer object on successful parse.
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// Note that WebPDemuxer keeps internal pointers to 'data' memory segment.
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// If this data is volatile, the demuxer object should be deleted (by calling
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// WebPDemuxDelete()) and WebPDemuxPartial() called again on the new data.
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// This is usually an inexpensive operation.
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static WEBP_INLINE WebPDemuxer* WebPDemuxPartial(
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const WebPData* data, WebPDemuxState* state) {
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return WebPDemuxInternal(data, 1, state, WEBP_DEMUX_ABI_VERSION);
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}
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// Frees memory associated with 'dmux'.
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WEBP_EXTERN(void) WebPDemuxDelete(WebPDemuxer* dmux);
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//------------------------------------------------------------------------------
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// Data/information extraction.
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typedef enum WebPFormatFeature {
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WEBP_FF_FORMAT_FLAGS, // Extended format flags present in the 'VP8X' chunk.
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WEBP_FF_CANVAS_WIDTH,
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WEBP_FF_CANVAS_HEIGHT,
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WEBP_FF_LOOP_COUNT,
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WEBP_FF_BACKGROUND_COLOR,
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WEBP_FF_FRAME_COUNT // Number of frames present in the demux object.
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// In case of a partial demux, this is the number of
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// frames seen so far, with the last frame possibly
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// being partial.
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} WebPFormatFeature;
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// Get the 'feature' value from the 'dmux'.
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// NOTE: values are only valid if WebPDemux() was used or WebPDemuxPartial()
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// returned a state > WEBP_DEMUX_PARSING_HEADER.
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WEBP_EXTERN(uint32_t) WebPDemuxGetI(
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const WebPDemuxer* dmux, WebPFormatFeature feature);
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//------------------------------------------------------------------------------
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// Frame iteration.
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struct WebPIterator {
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int frame_num;
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int num_frames; // equivalent to WEBP_FF_FRAME_COUNT.
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int fragment_num;
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int num_fragments;
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int x_offset, y_offset; // offset relative to the canvas.
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int width, height; // dimensions of this frame or fragment.
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int duration; // display duration in milliseconds.
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WebPMuxAnimDispose dispose_method; // dispose method for the frame.
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int complete; // true if 'fragment' contains a full frame. partial images
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// may still be decoded with the WebP incremental decoder.
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WebPData fragment; // The frame or fragment given by 'frame_num' and
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// 'fragment_num'.
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int has_alpha; // True if the frame or fragment contains transparency.
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WebPMuxAnimBlend blend_method; // Blend operation for the frame.
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uint32_t pad[2]; // padding for later use.
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void* private_; // for internal use only.
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};
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// Retrieves frame 'frame_number' from 'dmux'.
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// 'iter->fragment' points to the first fragment on return from this function.
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// Individual fragments may be extracted using WebPDemuxSelectFragment().
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// Setting 'frame_number' equal to 0 will return the last frame of the image.
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// Returns false if 'dmux' is NULL or frame 'frame_number' is not present.
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// Call WebPDemuxReleaseIterator() when use of the iterator is complete.
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// NOTE: 'dmux' must persist for the lifetime of 'iter'.
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WEBP_EXTERN(int) WebPDemuxGetFrame(
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const WebPDemuxer* dmux, int frame_number, WebPIterator* iter);
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// Sets 'iter->fragment' to point to the next ('iter->frame_num' + 1) or
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// previous ('iter->frame_num' - 1) frame. These functions do not loop.
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// Returns true on success, false otherwise.
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WEBP_EXTERN(int) WebPDemuxNextFrame(WebPIterator* iter);
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WEBP_EXTERN(int) WebPDemuxPrevFrame(WebPIterator* iter);
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// Sets 'iter->fragment' to reflect fragment number 'fragment_num'.
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// Returns true if fragment 'fragment_num' is present, false otherwise.
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WEBP_EXTERN(int) WebPDemuxSelectFragment(WebPIterator* iter, int fragment_num);
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// Releases any memory associated with 'iter'.
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// Must be called before any subsequent calls to WebPDemuxGetChunk() on the same
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// iter. Also, must be called before destroying the associated WebPDemuxer with
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// WebPDemuxDelete().
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WEBP_EXTERN(void) WebPDemuxReleaseIterator(WebPIterator* iter);
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//------------------------------------------------------------------------------
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// Chunk iteration.
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struct WebPChunkIterator {
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// The current and total number of chunks with the fourcc given to
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// WebPDemuxGetChunk().
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int chunk_num;
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int num_chunks;
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WebPData chunk; // The payload of the chunk.
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uint32_t pad[6]; // padding for later use
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void* private_;
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};
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// Retrieves the 'chunk_number' instance of the chunk with id 'fourcc' from
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// 'dmux'.
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// 'fourcc' is a character array containing the fourcc of the chunk to return,
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// e.g., "ICCP", "XMP ", "EXIF", etc.
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// Setting 'chunk_number' equal to 0 will return the last chunk in a set.
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// Returns true if the chunk is found, false otherwise. Image related chunk
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// payloads are accessed through WebPDemuxGetFrame() and related functions.
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// Call WebPDemuxReleaseChunkIterator() when use of the iterator is complete.
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// NOTE: 'dmux' must persist for the lifetime of the iterator.
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WEBP_EXTERN(int) WebPDemuxGetChunk(const WebPDemuxer* dmux,
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const char fourcc[4], int chunk_number,
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WebPChunkIterator* iter);
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// Sets 'iter->chunk' to point to the next ('iter->chunk_num' + 1) or previous
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// ('iter->chunk_num' - 1) chunk. These functions do not loop.
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// Returns true on success, false otherwise.
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WEBP_EXTERN(int) WebPDemuxNextChunk(WebPChunkIterator* iter);
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WEBP_EXTERN(int) WebPDemuxPrevChunk(WebPChunkIterator* iter);
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// Releases any memory associated with 'iter'.
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// Must be called before destroying the associated WebPDemuxer with
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// WebPDemuxDelete().
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WEBP_EXTERN(void) WebPDemuxReleaseChunkIterator(WebPChunkIterator* iter);
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//------------------------------------------------------------------------------
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif /* WEBP_WEBP_DEMUX_H_ */
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