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diff --git a/media/libwebp/README.mux b/media/libwebp/README.mux new file mode 100644 index 000000000..04fedd163 --- /dev/null +++ b/media/libwebp/README.mux @@ -0,0 +1,223 @@ + __ __ ____ ____ ____ __ __ _ __ __ + / \\/ \/ _ \/ _ \/ _ \/ \ \/ \___/_ / _\ + \ / __/ _ \ __/ / / (_/ /__ + \__\__/\_____/_____/__/ \__//_/\_____/__/___/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 |