mirror of
https://github.com/webmproject/libwebp.git
synced 2024-12-26 05:38:22 +01:00
b6f756e82b
- prefer https - metadataworkinggroup.org/com seem to be offline; the web archive link was obtained from exiftool: https://exiftool.org/TagNames/MWG.html - fix kramdown link, rubyforge has been gone a long time - fix png/zlib links Bug: webp:544 Bug: b/202302177 Change-Id: Id69de4553e7baf00393f12a2c1acb262443a1a93
151 lines
4.7 KiB
Groff
151 lines
4.7 KiB
Groff
.\" Hey, EMACS: -*- nroff -*-
|
|
.TH DWEBP 1 "November 17, 2021"
|
|
.SH NAME
|
|
dwebp \- decompress a WebP file to an image file
|
|
.SH SYNOPSIS
|
|
.B dwebp
|
|
.RI [ options ] " input_file.webp
|
|
.br
|
|
.SH DESCRIPTION
|
|
This manual page documents the
|
|
.B dwebp
|
|
command.
|
|
.PP
|
|
\fBdwebp\fP decompresses WebP files into PNG, PAM, PPM or PGM images.
|
|
Note: Animated WebP files are not supported.
|
|
.SH OPTIONS
|
|
The basic options are:
|
|
.TP
|
|
.B \-h
|
|
Print usage summary.
|
|
.TP
|
|
.B \-version
|
|
Print the version number (as major.minor.revision) and exit.
|
|
.TP
|
|
.BI \-o " string
|
|
Specify the name of the output file (as PNG format by default).
|
|
Using "-" as output name will direct output to 'stdout'.
|
|
.TP
|
|
.BI \-\- " string
|
|
Explicitly specify the input file. This option is useful if the input
|
|
file starts with an '\-' for instance. This option must appear \fBlast\fP.
|
|
Any other options afterward will be ignored. If the input file is "\-",
|
|
the data will be read from \fIstdin\fP instead of a file.
|
|
.TP
|
|
.B \-bmp
|
|
Change the output format to uncompressed BMP.
|
|
.TP
|
|
.B \-tiff
|
|
Change the output format to uncompressed TIFF.
|
|
.TP
|
|
.B \-pam
|
|
Change the output format to PAM (retains alpha).
|
|
.TP
|
|
.B \-ppm
|
|
Change the output format to PPM (discards alpha).
|
|
.TP
|
|
.B \-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.
|
|
.TP
|
|
.B \-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.
|
|
.TP
|
|
.B \-nofancy
|
|
Don't use the fancy upscaler for YUV420. This may lead to jaggy
|
|
edges (especially the red ones), but should be faster.
|
|
.TP
|
|
.B \-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.
|
|
.TP
|
|
.BI \-dither " strength
|
|
Specify a dithering \fBstrength\fP 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.
|
|
.TP
|
|
.BI \-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.
|
|
.TP
|
|
.B \-nodither
|
|
Disable all dithering (default).
|
|
.TP
|
|
.B \-mt
|
|
Use multi-threading for decoding, if possible.
|
|
.TP
|
|
.BI \-crop " x_position y_position width height
|
|
Crop the decoded picture to a rectangle with top-left corner at coordinates
|
|
(\fBx_position\fP, \fBy_position\fP) and size \fBwidth\fP x \fBheight\fP.
|
|
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 \fIbefore\fP any scaling.
|
|
.TP
|
|
.B \-flip
|
|
Flip decoded image vertically (can be useful for OpenGL textures for instance).
|
|
.TP
|
|
\fB\-resize\fR, \fB\-scale\fI width height\fR
|
|
Rescale the decoded picture to dimension \fBwidth\fP x \fBheight\fP. 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 \fIafter\fP cropping.
|
|
If either (but not both) of the \fBwidth\fP or \fBheight\fP parameters is 0,
|
|
the value will be calculated preserving the aspect-ratio.
|
|
.TP
|
|
.B \-quiet
|
|
Do not print anything.
|
|
.TP
|
|
.B \-v
|
|
Print extra information (decoding time in particular).
|
|
.TP
|
|
.B \-noasm
|
|
Disable all assembly optimizations.
|
|
|
|
.SH BUGS
|
|
Please report all bugs to the issue tracker:
|
|
https://bugs.chromium.org/p/webp
|
|
.br
|
|
Patches welcome! See this page to get started:
|
|
https://www.webmproject.org/code/contribute/submitting\-patches/
|
|
|
|
.SH EXAMPLES
|
|
dwebp picture.webp \-o output.png
|
|
.br
|
|
dwebp picture.webp \-ppm \-o output.ppm
|
|
.br
|
|
dwebp \-o output.ppm \-\- \-\-\-picture.webp
|
|
.br
|
|
cat picture.webp | dwebp \-o \- \-\- \- > output.ppm
|
|
|
|
.SH AUTHORS
|
|
\fBdwebp\fP is a part of libwebp and was written by the WebP team.
|
|
.br
|
|
The latest source tree is available at
|
|
https://chromium.googlesource.com/webm/libwebp
|
|
.PP
|
|
This manual page was written by Pascal Massimino <pascal.massimino@gmail.com>,
|
|
for the Debian project (and may be used by others).
|
|
|
|
.SH SEE ALSO
|
|
.BR cwebp (1),
|
|
.BR gif2webp (1),
|
|
.BR webpmux (1)
|
|
.br
|
|
Please refer to https://developers.google.com/speed/webp/ for additional
|
|
information.
|
|
.SS Output file format details
|
|
PAM: http://netpbm.sourceforge.net/doc/pam.html
|
|
.br
|
|
PGM: http://netpbm.sourceforge.net/doc/pgm.html
|
|
.br
|
|
PPM: http://netpbm.sourceforge.net/doc/ppm.html
|
|
.br
|
|
PNG: http://www.libpng.org/pub/png/png-sitemap.html#info
|