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dwebp(1) [centos man page]

DWEBP(1)						      General Commands Manual							  DWEBP(1)

dwebp - decompress a WebP file to an image file SYNOPSIS
dwebp [options] input_file.webp DESCRIPTION
This manual page documents the dwebp command. dwebp decompresses WebP files into PNG, PAM, PPM or PGM images. OPTIONS
The basic options are: -h Print usage summary. -version Print the version number (as major.minor.revision) and exit. -o string Specify the name of the output file (as PNG format by default). -pam Change the output format to PAM (retains alpha). -ppm Change the output format to PPM (discards alpha). -pgm Change the output format to PGM. The output consists of luma/chroma samples instead of RGB, using the ICM4 layout. This option is mainly for verification and debugging purposes. -yuv Change the output format to raw YUV. The output consists of luma/chroma-U/chroma-V samples instead of RGB, saved sequentially as individual planes. This option is mainly for verification and debugging purposes. -nofancy Don't use the fancy upscaler for YUV420. This may lead to jaggy edges (especially the red ones), but should be faster. -nofilter Don't use the in-loop filtering process even if it is required by the bitstream. This may produce visible blocks on the non-compli- ant output, but will make the decoding faster. -mt Use multi-threading for decoding, if possible. -crop x_position y_position width height Crop the decoded picture to a rectangle with top-left corner at coordinates (x_position, y_position) and size width x height. This cropping area must be fully contained within the source rectangle. The top-left corner will be snapped to even coordinates if needed. This option is meant to reduce the memory needed for cropping large images. Note: the cropping is applied before any scal- ing. -scale width height Rescale the decoded picture to dimension width x height. This option is mostly intended to reducing the memory needed to decode large images, when only a small version is needed (thumbnail, preview, etc.). Note: scaling is applied after cropping. -v Print extra information (decoding time in particular). -noasm Disable all assembly optimizations. BUGS
Please report all bugs to our issue tracker: Patches welcome! See this page to get started: EXAMPLES
dwebp picture.webp -o output.png dwebp picture.webp -ppm -o output.ppm AUTHORS
dwebp was written by the WebP team. The latest source tree is available at This manual page was written by Pascal Massimino <>, for the Debian project (and may be used by others). SEE ALSO
cwebp(1), webpmux(1), gif2webp(1). Please refer to for additional information. Output file format details PAM: PGM: PPM: PNG: February 01, 2013 DWEBP(1)

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y4mtopnm(1)							MJPEG tools manual						       y4mtopnm(1)

y4mtopnm - Convert a YUV4MPEG2 stream to PNM images SYNOPSIS
y4mtopnm [options] DESCRIPTION
y4mtopnm converts a YUV4MPEG2 stream into a sequence of raw PPM, PGM, or PAM images. (Technically, "pnm" comprises the PPM, PGM and PBM formats. PAM is a fourth format, which can effectively contain any of the other three, and more.) Output is to stdout (but feel free to have the shell redirect to a file). Input is read from stdin, like all other YUV4MPEG2 filters and tools. YUV4MPEG2 streams contain frames using the Y'CbCr colorspace (ITU-R BT.601). For 4:4:4 (color) streams, y4mtopnm will convert each pixel to the usual R'G'B' colorspace used for computer graphics, and pro- duce PPM images. "MONO" (luma-only) streams will be converted to full-range [0,255] grayscale and output as PGM images. YUV4MPEG2 streams may (often!) have subsampled chroma planes, but y4mtopnm will not process them (except in the special 'flatten' mode; see below). Subsampled streams will need to be converted to 4:4:4 using a tool such as y4mscaler. If y4mtopnm is given a "444ALPHA" stream (4:4:4 video with an 8-bit alpha channel), the results depend on whether or not the "-P" option is specified. With "-P", it will produce PAM images with a TUPLTYPE of RGB_ALPHA, containing both color and alpha channel data. Without "-P", it will produce pairs of PPM and PGM images: a PPM for the color pixels followed by a PGM for the alpha channel data. (Such a sequence of interspersed PPM and PGM images cannot be later re-processed by pnmtoy4m. This feature is mostly for quick and easy stream debugging.) If multiple output images are generated, they are simply output one after another. If you want to turn such a "multi-image" stream/file into individual files, use pnmsplit. (Some PNM filters can process multi-image files/streams; however, many written before June 2000 will only process the first image.) y4mtopnm and pnmtoy4m are inverses of each other; you can typically pipe the output of one into the other, and vice-versa (except for the "444ALPHA" case noted above and the "mixed-mode" case noted below). Note that the colorspace operations can be lossy in both directions (due to range-compression and/or quantization). And, when converting to PNM, information on interlacing and sample aspect ratio of a stream is lost (but can be reconstructed by supplying command-line arguments to pnmtoy4m). OPTIONS
y4mtopnm accepts the following options: -P Produce PAM format output, instead of PPM and/or PGM. PAM can encode a superset of PNM, but is not yet understood by as many graphics programs. (Indeed, surprisingly few of the NetPBM tools seem to understand it.) -D Produce a separate output image for each field of each frame. (Otherwise, a single image per frame, containing two interleaved fields, is created.) If the input stream is interlaced, the field-images are output in temporal order, i.e. the first image of a bottom-field-first stream will be the bottom-field. If the stream is progressive or has "mixed-mode" interlacing, then the temporal order is ambiguous, and the top-field will always be output first. Note that it will not be possible to later use pnmtoy4m to reconstruct a "mixed-mode" stream from a sequence of PNM/PAM images. -f Produce a special 'flattened' output, most useful for analyzing and debugging streams. All the planes of a frame/field are tiled together into an enlarged PGM (or grayscale PAM) output image as follows: +-----+ +-----+ 4:4:4 | Y | 4:4:4 w/alpha | Y | +-----+ +-----+ | Cb | | Cb | +-----+ +-----+ | Cr | | Cr | +-----+ +-----+ | A | +-----+ +-----+ 4:2:2, | Y | 4:2:0 +--+--+ +-----+--+--+ |Cb|Cr| 4:1:1 | Y |Cb|Cr| +--+--+ +-----+--+--+ +-----+ MONO | Y | +-----+ In this mode, any YUV4MPEG2 chroma format is accepted, but no upsampling or colorspace conversion is performed. This is essentially just a reformatting/permutation of the original data from the input stream into a PGM image container. All the other command-line flags continue to have the same effect on output. -v [0,1,2] Set verbosity level. 0 = warnings and errors only. 1 = add informative messages, too. 2 = add chatty debugging message, too. EXAMPLES
To turn the first 15 frames of an (MJPEG or DV) AVI file into individual PPM files: lav2yuv -f 15 your-video.avi | y4mscaler -O chromass=444 | y4mtopnm | pnmsplit - "your-video-%d.ppm" AUTHOR
This manual page was written by Matt Marjanovic. If you have questions, remarks, problems or you just want to contact the developers, the main mailing list for the MJPEG-tools is: For more info, see our website at SEE ALSO
pam(5), pgm(5), pnm(5), ppm(5), pnmtoy4m(1), mjpegtools(1), mpeg2enc(1), lav2yuv(1), pnmsplit(1), y4mscaler(1) MJPEG Linux Square 28 April 2004 y4mtopnm(1)
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