include/webp/demux.h

// Copyright 2012 Google Inc. All Rights Reserved.
//
// This code is licensed under the same terms as WebM:
//  Software License Agreement:  http://www.webmproject.org/license/software/
//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
// Demux API.
// Enables extraction of image and extended format data from WebP files.

// TODO(urvang): Add an example code snippet (similar to mux.h).

#ifndef WEBP_WEBP_DEMUX_H_
#define WEBP_WEBP_DEMUX_H_

#include "./format_constants.h"
#include "./mux_types.h"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#define WEBP_DEMUX_ABI_VERSION 0x0100    // MAJOR(8b) + MINOR(8b)

typedef struct WebPDemuxer WebPDemuxer;
#if !(defined(__cplusplus) || defined(c_plusplus))
typedef enum WebPDemuxState WebPDemuxState;
typedef enum WebPFormatFeature WebPFormatFeature;
#endif
typedef struct WebPIterator WebPIterator;
typedef struct WebPChunkIterator WebPChunkIterator;

//------------------------------------------------------------------------------
// Life of a Demux object

enum WebPDemuxState {
  WEBP_DEMUX_PARSING_HEADER,  // Not enough data to parse full header.
  WEBP_DEMUX_PARSED_HEADER,   // Header parsing complete, data may be available.
  WEBP_DEMUX_DONE             // Entire file has been parsed.
};

// Internal, version-checked, entry point
WEBP_EXTERN(WebPDemuxer*) WebPDemuxInternal(
    const WebPData*, int, WebPDemuxState*, int);

// Parses the WebP file given by 'data'.
// A complete WebP file must be present in 'data' for the function to succeed.
// Returns a WebPDemuxer object on successful parse, NULL otherwise.
static WEBP_INLINE WebPDemuxer* WebPDemux(const WebPData* data) {
  return WebPDemuxInternal(data, 0, NULL, WEBP_DEMUX_ABI_VERSION);
}

// Parses the WebP file given by 'data'.
// If 'state' is non-NULL it will be set to indicate the status of the demuxer.
// Returns a WebPDemuxer object on successful parse, NULL otherwise.
static WEBP_INLINE WebPDemuxer* WebPDemuxPartial(
    const WebPData* data, WebPDemuxState* state) {
  return WebPDemuxInternal(data, 1, state, WEBP_DEMUX_ABI_VERSION);
}

// Frees memory associated with 'dmux'.
WEBP_EXTERN(void) WebPDemuxDelete(WebPDemuxer* dmux);

//------------------------------------------------------------------------------
// Data/information extraction.

enum WebPFormatFeature {
  WEBP_FF_FORMAT_FLAGS,  // Extended format flags present in the 'VP8X' chunk.
  WEBP_FF_CANVAS_WIDTH,
  WEBP_FF_CANVAS_HEIGHT,
  WEBP_FF_LOOP_COUNT,
  WEBP_FF_BACKGROUND_COLOR
};

// Get the 'feature' value from the 'dmux'.
// NOTE: values are only valid if WebPDemux() was used or WebPDemuxPartial()
// returned a state > WEBP_DEMUX_PARSING_HEADER.
WEBP_EXTERN(uint32_t) WebPDemuxGetI(
    const WebPDemuxer* dmux, WebPFormatFeature feature);

//------------------------------------------------------------------------------
// Frame iteration.

struct WebPIterator {
  int frame_num;
  int num_frames;
  int fragment_num;
  int num_fragments;
  int x_offset, y_offset;  // offset relative to the canvas.
  int width, height;       // dimensions of this frame or fragment.
  int duration;            // display duration in milliseconds.
  WebPMuxAnimDispose dispose_method;  // dispose method for the frame.
  int complete;   // true if 'fragment' contains a full frame. partial images
                  // may still be decoded with the WebP incremental decoder.
  WebPData fragment;  // The frame or fragment given by 'frame_num' and
                      // 'fragment_num'.

  uint32_t pad[4];         // padding for later use.
  void* private_;          // for internal use only.
};

// Retrieves frame 'frame_number' from 'dmux'.
// 'iter->fragment' points to the first fragment on return from this function.
// Individual fragments may be extracted using WebPDemuxSetFragment().
// Setting 'frame_number' equal to 0 will return the last frame of the image.
// Returns false if 'dmux' is NULL or frame 'frame_number' is not present.
// Call WebPDemuxReleaseIterator() when use of the iterator is complete.
// NOTE: 'dmux' must persist for the lifetime of 'iter'.
WEBP_EXTERN(int) WebPDemuxGetFrame(
    const WebPDemuxer* dmux, int frame_number, WebPIterator* iter);

// Sets 'iter->fragment' to point to the next ('iter->frame_num' + 1) or
// previous ('iter->frame_num' - 1) frame. These functions do not loop.
// Returns true on success, false otherwise.
WEBP_EXTERN(int) WebPDemuxNextFrame(WebPIterator* iter);
WEBP_EXTERN(int) WebPDemuxPrevFrame(WebPIterator* iter);

// Sets 'iter->fragment' to reflect fragment number 'fragment_num'.
// Returns true if fragment 'fragment_num' is present, false otherwise.
WEBP_EXTERN(int) WebPDemuxSelectFragment(WebPIterator* iter, int fragment_num);

// Releases any memory associated with 'iter'.
// Must be called before destroying the associated WebPDemuxer with
// WebPDemuxDelete().
WEBP_EXTERN(void) WebPDemuxReleaseIterator(WebPIterator* iter);

//------------------------------------------------------------------------------
// Chunk iteration.

struct WebPChunkIterator {
  // The current and total number of chunks with the fourcc given to
  // WebPDemuxGetChunk().
  int chunk_num;
  int num_chunks;
  WebPData chunk;    // The payload of the chunk.

  uint32_t pad[6];   // padding for later use
  void* private_;
};

// Retrieves the 'chunk_number' instance of the chunk with id 'fourcc' from
// 'dmux'.
// 'fourcc' is a character array containing the fourcc of the chunk to return,
// e.g., "ICCP", "XMP ", "EXIF", etc.
// Setting 'chunk_number' equal to 0 will return the last chunk in a set.
// Returns true if the chunk is found, false otherwise. Image related chunk
// payloads are accessed through WebPDemuxGetFrame() and related functions.
// Call WebPDemuxReleaseChunkIterator() when use of the iterator is complete.
// NOTE: 'dmux' must persist for the lifetime of the iterator.
WEBP_EXTERN(int) WebPDemuxGetChunk(const WebPDemuxer* dmux,
                                   const char fourcc[4], int chunk_number,
                                   WebPChunkIterator* iter);

// Sets 'iter->chunk' to point to the next ('iter->chunk_num' + 1) or previous
// ('iter->chunk_num' - 1) chunk. These functions do not loop.
// Returns true on success, false otherwise.
WEBP_EXTERN(int) WebPDemuxNextChunk(WebPChunkIterator* iter);
WEBP_EXTERN(int) WebPDemuxPrevChunk(WebPChunkIterator* iter);

// Releases any memory associated with 'iter'.
// Must be called before destroying the associated WebPDemuxer with
// WebPDemuxDelete().
WEBP_EXTERN(void) WebPDemuxReleaseChunkIterator(WebPChunkIterator* iter);

//------------------------------------------------------------------------------

#if defined(__cplusplus) || defined(c_plusplus)
}    // extern "C"
#endif

#endif  /* WEBP_WEBP_DEMUX_H_ */