Tribblix: manual page: dwebp.1

DWEBP(1) User Commands 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.
Note: Animated WebP files are not supported.

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:
https://bugs.chromium.org/p/webp
Patches welcome! See this page to get started:
https://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
https://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).