src/third_party/libwebp/man/gif2webp.1

.\"                                      Hey, EMACS: -*- nroff -*-
.TH GIF2WEBP 1 "January 25, 2018"
.SH NAME
gif2webp \- Convert a GIF image to WebP
.SH SYNOPSIS
.B gif2webp
.RI [ options ] " input_file.gif \-o output_file.webp
.br
.SH DESCRIPTION
This manual page documents the
.B gif2webp
command.
.PP
\fBgif2webp\fP converts a GIF image to a WebP image.
.SH OPTIONS
The basic options are:
.TP
.BI \-o " string
Specify the name of the output WebP file. If omitted, \fBgif2webp\fP will
perform conversion but only report statistics.
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 \-h, \-help
Usage information.
.TP
.B \-version
Print the version number (as major.minor.revision) and exit.
.TP
.B \-lossy
Encode the image using lossy compression.
.TP
.B \-mixed
Mixed compression mode: optimize compression of the image by picking either
lossy or lossless compression for each frame heuristically.
.TP
.BI \-q " float
Specify the compression factor for RGB channels between 0 and 100. The default
is 75.
.br
In case of lossless compression (default), a small factor enables faster
compression speed, but produces a larger file. Maximum compression is achieved
by using a value of 100.
.br
In case of lossy compression (specified by the \-lossy option), a small factor
produces a smaller file with lower quality. Best quality is achieved by using a
value of 100.
.TP
.BI \-m " int
Specify the compression method to use. This parameter controls the
trade off between encoding speed and the compressed file size and quality.
Possible values range from 0 to 6. Default value is 4.
When higher values are used, the encoder will spend more time inspecting
additional encoding possibilities and decide on the quality gain.
Lower value can result is faster processing time at the expense of
larger file size and lower compression quality.
.TP
.BI \-min_size
Encode image to achieve smallest size. This disables key frame insertion and
picks the dispose method resulting in smallest output for each frame. It uses
lossless compression by default, but can be combined with \-q, \-m, \-lossy or
\-mixed options.
.TP
.BI \-kmin " int
.TP
.BI \-kmax " int
Specify the minimum and maximum distance between consecutive key frames
(independently decodable frames) in the output animation. The tool will insert
some key frames into the output animation as needed so that this criteria is
satisfied.
.br
A 'kmax' value of 0 will turn off insertion of key frames. A 'kmax' value of 1
will result in all frames being key frames. 'kmin' value is not taken into
account in both these special cases.
Typical values are in the range 3 to 30. Default values are kmin = 9,
kmax = 17 for lossless compression and kmin = 3, kmax = 5 for lossy compression.
.br
These two options are relevant only for animated images with large number of
frames (>50).
.br
When lower values are used, more frames will be converted to key frames. This
may lead to smaller number of frames required to decode a frame on average,
thereby improving the decoding performance. But this may lead to slightly bigger
file sizes.
Higher values may lead to worse decoding performance, but smaller file sizes.
.br
Some restrictions:
.br
(i) kmin < kmax,
.br
(ii) kmin >= kmax / 2 + 1 and
.br
(iii) kmax - kmin <= 30.
.br
If any of these restrictions are not met, they will be enforced automatically.
.TP
.BI \-metadata " string
A comma separated list of metadata to copy from the input to the output if
present.
Valid values: \fBall\fP, \fBnone\fP, \fBicc\fP, \fBxmp\fP.
The default is \fBxmp\fP.
.TP
.BI \-f " int
For lossy encoding only (specified by the \-lossy option). Specify the strength
of the deblocking filter, between 0 (no filtering) and 100 (maximum filtering).
A value of 0 will turn off any filtering. Higher value will increase the
strength of the filtering process applied after decoding the picture. The higher
the value the smoother the picture will appear. Typical values are usually in
the range of 20 to 50.
.TP
.B \-mt
Use multi-threading for encoding, if possible.
.TP
.B \-loop_compatibility
If enabled, handle the loop information in a compatible fashion for Chrome
version prior to M62 (inclusive) and Firefox.
.TP
.B \-v
Print extra information.
.TP
.B \-quiet
Do not print anything.

.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:
http://www.webmproject.org/code/contribute/submitting-patches/

.SH EXAMPLES
gif2webp picture.gif \-o picture.webp
.br
gif2webp \-q 70 picture.gif \-o picture.webp
.br
gif2webp \-lossy \-m 3 picture.gif \-o picture_lossy.webp
.br
gif2webp \-lossy \-f 50 picture.gif \-o picture.webp
.br
gif2webp \-q 70 \-o picture.webp \-\- \-\-\-picture.gif
.br
cat picture.gif | gif2webp \-o \- \-\- \- > output.webp

.SH AUTHORS
\fBgif2webp\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 Urvang Joshi <urvang@google.com>, for the
Debian project (and may be used by others).

.SH SEE ALSO
.BR cwebp (1),
.BR dwebp (1),
.BR webpmux (1)
.br
Please refer to http://developers.google.com/speed/webp/ for additional
information.