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.
- -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.
- -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:
http://code.google.com/p/webp/issues
Patches welcome! See this page to get started:
http://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 was written by the WebP team.
The latest source tree is available at
http://www.webmproject.org/code
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
http://developers.google.com/speed/webp/ for additional
information.
PAM:
http://netpbm.sourceforge.net/doc/pam.html
PGM:
http://netpbm.sourceforge.net/doc/pgm.html
PPM:
http://netpbm.sourceforge.net/doc/ppm.html
PNG:
http://www.libpng.org/pub/png/png-sitemap.html#info