257 lines
8.7 KiB
Plaintext
257 lines
8.7 KiB
Plaintext
__ __ ____ ____ ____ __ __ _ __ __
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/ \\/ \/ _ \/ _ \/ _ \/ \ \/ \___/_ / _\
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\ / __/ _ \ __/ / / (_/ /__
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\__\__/\_____/_____/__/ \__//_/\_____/__/___/v1.0.2
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Description:
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============
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WebPMux: set of two libraries 'Mux' and 'Demux' for creation, extraction and
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manipulation of an extended format WebP file, which can have features like
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color profile, metadata and animation. Reference command-line tools 'webpmux'
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and 'vwebp' as well as the WebP container specification
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'doc/webp-container-spec.txt' are also provided in this package.
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WebP Mux tool:
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==============
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The examples/ directory contains a tool (webpmux) for manipulating WebP
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files. The webpmux tool can be used to create an extended format WebP file and
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also to extract or strip relevant data from such a file.
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A list of options is available using the -help command line flag:
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> webpmux -help
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Usage: webpmux -get GET_OPTIONS INPUT -o OUTPUT
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webpmux -set SET_OPTIONS INPUT -o OUTPUT
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webpmux -duration DURATION_OPTIONS [-duration ...]
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INPUT -o OUTPUT
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webpmux -strip STRIP_OPTIONS INPUT -o OUTPUT
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webpmux -frame FRAME_OPTIONS [-frame...] [-loop LOOP_COUNT]
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[-bgcolor BACKGROUND_COLOR] -o OUTPUT
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webpmux -info INPUT
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webpmux [-h|-help]
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webpmux -version
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webpmux argument_file_name
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GET_OPTIONS:
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Extract relevant data:
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icc get ICC profile
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exif get EXIF metadata
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xmp get XMP metadata
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frame n get nth frame
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SET_OPTIONS:
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Set color profile/metadata:
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icc file.icc set ICC profile
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exif file.exif set EXIF metadata
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xmp file.xmp set XMP metadata
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where: 'file.icc' contains the ICC profile to be set,
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'file.exif' contains the EXIF metadata to be set
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'file.xmp' contains the XMP metadata to be set
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DURATION_OPTIONS:
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Set duration of selected frames:
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duration set duration for each frames
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duration,frame set duration of a particular frame
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duration,start,end set duration of frames in the
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interval [start,end])
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where: 'duration' is the duration in milliseconds
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'start' is the start frame index
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'end' is the inclusive end frame index
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The special 'end' value '0' means: last frame.
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STRIP_OPTIONS:
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Strip color profile/metadata:
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icc strip ICC profile
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exif strip EXIF metadata
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xmp strip XMP metadata
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FRAME_OPTIONS(i):
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Create animation:
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file_i +di+[xi+yi[+mi[bi]]]
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where: 'file_i' is the i'th animation frame (WebP format),
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'di' is the pause duration before next frame,
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'xi','yi' specify the image offset for this frame,
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'mi' is the dispose method for this frame (0 or 1),
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'bi' is the blending method for this frame (+b or -b)
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LOOP_COUNT:
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Number of times to repeat the animation.
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Valid range is 0 to 65535 [Default: 0 (infinite)].
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BACKGROUND_COLOR:
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Background color of the canvas.
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A,R,G,B
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where: 'A', 'R', 'G' and 'B' are integers in the range 0 to 255 specifying
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the Alpha, Red, Green and Blue component values respectively
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[Default: 255,255,255,255]
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INPUT & OUTPUT are in WebP format.
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Note: The nature of EXIF, XMP and ICC data is not checked and is assumed to be
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valid.
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Note: if a single file name is passed as the argument, the arguments will be
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tokenized from this file. The file name must not start with the character '-'.
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Visualization tool:
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===================
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The examples/ directory also contains a tool (vwebp) for viewing WebP files.
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It decodes the image and visualizes it using OpenGL. See the libwebp README
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for details on building and running this program.
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Mux API:
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========
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The Mux API contains methods for adding data to and reading data from WebP
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files. This API currently supports XMP/EXIF metadata, ICC profile and animation.
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Other features may be added in subsequent releases.
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Example#1 (pseudo code): Creating a WebPMux object with image data, color
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profile and XMP metadata.
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int copy_data = 0;
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WebPMux* mux = WebPMuxNew();
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// ... (Prepare image data).
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WebPMuxSetImage(mux, &image, copy_data);
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// ... (Prepare ICC profile data).
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WebPMuxSetChunk(mux, "ICCP", &icc_profile, copy_data);
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// ... (Prepare XMP metadata).
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WebPMuxSetChunk(mux, "XMP ", &xmp, copy_data);
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// Get data from mux in WebP RIFF format.
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WebPMuxAssemble(mux, &output_data);
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WebPMuxDelete(mux);
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// ... (Consume output_data; e.g. write output_data.bytes to file).
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WebPDataClear(&output_data);
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Example#2 (pseudo code): Get image and color profile data from a WebP file.
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int copy_data = 0;
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// ... (Read data from file).
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WebPMux* mux = WebPMuxCreate(&data, copy_data);
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WebPMuxGetFrame(mux, 1, &image);
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// ... (Consume image; e.g. call WebPDecode() to decode the data).
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WebPMuxGetChunk(mux, "ICCP", &icc_profile);
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// ... (Consume icc_profile).
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WebPMuxDelete(mux);
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free(data);
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For a detailed Mux API reference, please refer to the header file
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(src/webp/mux.h).
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Demux API:
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==========
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The Demux API enables extraction of images and extended format data from
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WebP files. This API currently supports reading of XMP/EXIF metadata, ICC
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profile and animated images. Other features may be added in subsequent
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releases.
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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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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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For a detailed Demux API reference, please refer to the header file
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(src/webp/demux.h).
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AnimEncoder API:
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================
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The AnimEncoder API can be used to create animated WebP images.
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Code example:
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WebPAnimEncoderOptions enc_options;
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WebPAnimEncoderOptionsInit(&enc_options);
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// ... (Tune 'enc_options' as needed).
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WebPAnimEncoder* enc = WebPAnimEncoderNew(width, height, &enc_options);
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while(<there are more frames>) {
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WebPConfig config;
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WebPConfigInit(&config);
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// ... (Tune 'config' as needed).
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WebPAnimEncoderAdd(enc, frame, duration, &config);
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}
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WebPAnimEncoderAssemble(enc, webp_data);
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WebPAnimEncoderDelete(enc);
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// ... (Write the 'webp_data' to a file, or re-mux it further).
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For a detailed AnimEncoder API reference, please refer to the header file
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(src/webp/mux.h).
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AnimDecoder API:
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================
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This AnimDecoder API allows decoding (possibly) animated WebP images.
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Code Example:
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WebPAnimDecoderOptions dec_options;
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WebPAnimDecoderOptionsInit(&dec_options);
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// Tune 'dec_options' as needed.
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WebPAnimDecoder* dec = WebPAnimDecoderNew(webp_data, &dec_options);
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WebPAnimInfo anim_info;
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WebPAnimDecoderGetInfo(dec, &anim_info);
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for (uint32_t i = 0; i < anim_info.loop_count; ++i) {
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while (WebPAnimDecoderHasMoreFrames(dec)) {
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uint8_t* buf;
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int timestamp;
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WebPAnimDecoderGetNext(dec, &buf, ×tamp);
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// ... (Render 'buf' based on 'timestamp').
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// ... (Do NOT free 'buf', as it is owned by 'dec').
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}
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WebPAnimDecoderReset(dec);
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}
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const WebPDemuxer* demuxer = WebPAnimDecoderGetDemuxer(dec);
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// ... (Do something using 'demuxer'; e.g. get EXIF/XMP/ICC data).
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WebPAnimDecoderDelete(dec);
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For a detailed AnimDecoder API reference, please refer to the header file
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(src/webp/demux.h).
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Bugs:
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=====
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Please report all bugs to the issue tracker:
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https://bugs.chromium.org/p/webp
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Patches welcome! See this page to get started:
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http://www.webmproject.org/code/contribute/submitting-patches/
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Discuss:
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========
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Email: webp-discuss@webmproject.org
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Web: http://groups.google.com/a/webmproject.org/group/webp-discuss
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