dwebp (1)

Leading comments

Hey, EMACS: 

(The comments found at the beginning of the groff file "man1/dwebp.1".)

NAME

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). Using "-" as output name will direct output to 'stdout'.

-- string

Explicitly specify the input file. This option is useful if the input file starts with an '-' for instance. This option must appear last. Any other options afterward will be ignored. If the input file is "-", the data will be read from stdin instead of a file.

-bmp

Change the output format to uncompressed BMP.

-tiff

Change the output format to uncompressed TIFF.

-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 IMC4 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-compliant output, but it will make the decoding faster.

-dither strength

Specify a dithering strength between 0 and 100. Dithering is a post-processing effect applied to chroma components in lossy compression. It helps by smoothing gradients and avoiding banding artifacts.

-alpha_dither

If the compressed file contains a transparency plane that was quantized during compression, this flag will allow dithering the reconstructed plane in order to generate smoother transparency gradients.

-nodither

Disable all dithering (default).

-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 scaling.

-flip

Flip decoded image vertically (can be useful for OpenGL textures for instance).

-resize, -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. If either (but not both) of the width or height parameters is 0, the value will be calculated preserving the aspect-ratio.

-quiet

Do not print anything.

-v

Print extra information (decoding time in particular).

-noasm

Disable all assembly optimizations.

BUGS

Please report all bugs to the issue tracker: bugs.chromium.org/p/webp
Patches welcome! See this page to get started: www.webmproject.org/code/contribute/submitting-patches

EXAMPLES

dwebp picture.webp -o output.png
dwebp picture.webp -ppm -o output.ppm
dwebp -o output.ppm -- ---picture.webp
cat picture.webp | dwebp -o - -- - > output.ppm

AUTHORS

dwebp is a part of libwebp and was written by the WebP team.
The latest source tree is available at chromium.googlesource.com/webm/libwebp

This manual page was written by Pascal Massimino <pascal.massimino@gmail.com>, for the Debian project (and may be used by others).

SEE ALSO

cwebp(1), gif2webp(1), webpmux(1)
Please refer to developers.google.com/speed/webp for additional information.

Output file format details

PAM: netpbm.sourceforge.net/doc/pam.html
PGM: netpbm.sourceforge.net/doc/pgm.html
PPM: netpbm.sourceforge.net/doc/ppm.html
PNG: www.libpng.org/pub/png/png-sitemap.html#info