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authorwolfbeast <mcwerewolf@gmail.com>2018-02-03 14:02:24 +0100
committerwolfbeast <mcwerewolf@gmail.com>2018-02-03 14:02:24 +0100
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+ __ __ ____ ____ ____ __ __ _ __ __
+ / \\/ \/ _ \/ _ \/ _ \/ \ \/ \___/_ / _\
+ \ / __/ _ \ __/ / / (_/ /__
+ \__\__/\_____/_____/__/ \__//_/\_____/__/___/v0.4.0
+
+
+Description:
+============
+
+WebPMux: set of two libraries 'Mux' and 'Demux' for creation, extraction and
+manipulation of an extended format WebP file, which can have features like
+color profile, metadata and animation. Reference command-line tools 'webpmux'
+and 'vwebp' as well as the WebP container specification
+'doc/webp-container-spec.txt' are also provided in this package.
+
+WebP Mux tool:
+==============
+
+The examples/ directory contains a tool (webpmux) for manipulating WebP
+files. The webpmux tool can be used to create an extended format WebP file and
+also to extract or strip relevant data from such a file.
+
+A list of options is available using the -help command line flag:
+
+> webpmux -help
+Usage: webpmux -get GET_OPTIONS INPUT -o OUTPUT
+ webpmux -set SET_OPTIONS INPUT -o OUTPUT
+ webpmux -duration DURATION_OPTIONS [-duration ...]
+ INPUT -o OUTPUT
+ webpmux -strip STRIP_OPTIONS INPUT -o OUTPUT
+ webpmux -frame FRAME_OPTIONS [-frame...] [-loop LOOP_COUNT]
+ [-bgcolor BACKGROUND_COLOR] -o OUTPUT
+ webpmux -info INPUT
+ webpmux [-h|-help]
+ webpmux -version
+
+GET_OPTIONS:
+ Extract relevant data:
+ icc get ICC profile
+ exif get EXIF metadata
+ xmp get XMP metadata
+ frame n get nth frame
+
+SET_OPTIONS:
+ Set color profile/metadata:
+ icc file.icc set ICC profile
+ exif file.exif set EXIF metadata
+ xmp file.xmp set XMP metadata
+ where: 'file.icc' contains the ICC profile to be set,
+ 'file.exif' contains the EXIF metadata to be set
+ 'file.xmp' contains the XMP metadata to be set
+
+DURATION_OPTIONS:
+ Set duration of selected frames:
+ duration set duration for each frames
+ duration,frame set duration of a particular frame
+ duration,start,end set duration of frames in the
+ interval [start,end])
+ where: 'duration' is the duration in milliseconds
+ 'start' is the start frame index
+ 'end' is the inclusive end frame index
+ The special 'end' value '0' means: last frame.
+
+STRIP_OPTIONS:
+ Strip color profile/metadata:
+ icc strip ICC profile
+ exif strip EXIF metadata
+ xmp strip XMP metadata
+
+FRAME_OPTIONS(i):
+ Create animation:
+ file_i +di+[xi+yi[+mi[bi]]]
+ where: 'file_i' is the i'th animation frame (WebP format),
+ 'di' is the pause duration before next frame,
+ 'xi','yi' specify the image offset for this frame,
+ 'mi' is the dispose method for this frame (0 or 1),
+ 'bi' is the blending method for this frame (+b or -b)
+
+LOOP_COUNT:
+ Number of times to repeat the animation.
+ Valid range is 0 to 65535 [Default: 0 (infinite)].
+
+BACKGROUND_COLOR:
+ Background color of the canvas.
+ A,R,G,B
+ where: 'A', 'R', 'G' and 'B' are integers in the range 0 to 255 specifying
+ the Alpha, Red, Green and Blue component values respectively
+ [Default: 255,255,255,255]
+
+INPUT & OUTPUT are in WebP format.
+
+Note: The nature of EXIF, XMP and ICC data is not checked and is assumed to be
+valid.
+
+Visualization tool:
+===================
+
+The examples/ directory also contains a tool (vwebp) for viewing WebP files.
+It decodes the image and visualizes it using OpenGL. See the libwebp README
+for details on building and running this program.
+
+Mux API:
+========
+The Mux API contains methods for adding data to and reading data from WebP
+files. This API currently supports XMP/EXIF metadata, ICC profile and animation.
+Other features may be added in subsequent releases.
+
+Example#1 (pseudo code): Creating a WebPMux object with image data, color
+profile and XMP metadata.
+
+ int copy_data = 0;
+ WebPMux* mux = WebPMuxNew();
+ // ... (Prepare image data).
+ WebPMuxSetImage(mux, &image, copy_data);
+ // ... (Prepare ICC profile data).
+ WebPMuxSetChunk(mux, "ICCP", &icc_profile, copy_data);
+ // ... (Prepare XMP metadata).
+ WebPMuxSetChunk(mux, "XMP ", &xmp, copy_data);
+ // Get data from mux in WebP RIFF format.
+ WebPMuxAssemble(mux, &output_data);
+ WebPMuxDelete(mux);
+ // ... (Consume output_data; e.g. write output_data.bytes to file).
+ WebPDataClear(&output_data);
+
+
+Example#2 (pseudo code): Get image and color profile data from a WebP file.
+
+ int copy_data = 0;
+ // ... (Read data from file).
+ WebPMux* mux = WebPMuxCreate(&data, copy_data);
+ WebPMuxGetFrame(mux, 1, &image);
+ // ... (Consume image; e.g. call WebPDecode() to decode the data).
+ WebPMuxGetChunk(mux, "ICCP", &icc_profile);
+ // ... (Consume icc_profile).
+ WebPMuxDelete(mux);
+ free(data);
+
+
+For a detailed Mux API reference, please refer to the header file
+(src/webp/mux.h).
+
+Demux API:
+==========
+The Demux API enables extraction of images and extended format data from
+WebP files. This API currently supports reading of XMP/EXIF metadata, ICC
+profile and animated images. Other features may be added in subsequent
+releases.
+
+Code example: Demuxing WebP data to extract all the frames, ICC profile
+and EXIF/XMP metadata.
+
+ WebPDemuxer* demux = WebPDemux(&webp_data);
+ uint32_t width = WebPDemuxGetI(demux, WEBP_FF_CANVAS_WIDTH);
+ uint32_t height = WebPDemuxGetI(demux, WEBP_FF_CANVAS_HEIGHT);
+ // ... (Get information about the features present in the WebP file).
+ uint32_t flags = WebPDemuxGetI(demux, WEBP_FF_FORMAT_FLAGS);
+
+ // ... (Iterate over all frames).
+ WebPIterator iter;
+ if (WebPDemuxGetFrame(demux, 1, &iter)) {
+ do {
+ // ... (Consume 'iter'; e.g. Decode 'iter.fragment' with WebPDecode(),
+ // ... and get other frame properties like width, height, offsets etc.
+ // ... see 'struct WebPIterator' below for more info).
+ } while (WebPDemuxNextFrame(&iter));
+ WebPDemuxReleaseIterator(&iter);
+ }
+
+ // ... (Extract metadata).
+ WebPChunkIterator chunk_iter;
+ if (flags & ICCP_FLAG) WebPDemuxGetChunk(demux, "ICCP", 1, &chunk_iter);
+ // ... (Consume the ICC profile in 'chunk_iter.chunk').
+ WebPDemuxReleaseChunkIterator(&chunk_iter);
+ if (flags & EXIF_FLAG) WebPDemuxGetChunk(demux, "EXIF", 1, &chunk_iter);
+ // ... (Consume the EXIF metadata in 'chunk_iter.chunk').
+ WebPDemuxReleaseChunkIterator(&chunk_iter);
+ if (flags & XMP_FLAG) WebPDemuxGetChunk(demux, "XMP ", 1, &chunk_iter);
+ // ... (Consume the XMP metadata in 'chunk_iter.chunk').
+ WebPDemuxReleaseChunkIterator(&chunk_iter);
+ WebPDemuxDelete(demux);
+
+
+For a detailed Demux API reference, please refer to the header file
+(src/webp/demux.h).
+
+AnimEncoder API:
+================
+The AnimEncoder API can be used to create animated WebP images.
+
+Code example:
+
+ WebPAnimEncoderOptions enc_options;
+ WebPAnimEncoderOptionsInit(&enc_options);
+ // ... (Tune 'enc_options' as needed).
+ WebPAnimEncoder* enc = WebPAnimEncoderNew(width, height, &enc_options);
+ while(<there are more frames>) {
+ WebPConfig config;
+ WebPConfigInit(&config);
+ // ... (Tune 'config' as needed).
+ WebPAnimEncoderAdd(enc, frame, duration, &config);
+ }
+ WebPAnimEncoderAssemble(enc, webp_data);
+ WebPAnimEncoderDelete(enc);
+ // ... (Write the 'webp_data' to a file, or re-mux it further).
+
+
+For a detailed AnimEncoder API reference, please refer to the header file
+(src/webp/mux.h).
+
+
+Bugs:
+=====
+
+Please report all bugs to the issue tracker:
+ https://bugs.chromium.org/p/webp
+Patches welcome! See this page to get started:
+ http://www.webmproject.org/code/contribute/submitting-patches/
+
+Discuss:
+========
+
+Email: webp-discuss@webmproject.org
+Web: http://groups.google.com/a/webmproject.org/group/webp-discuss