mirror of
https://github.com/webmproject/libwebp.git
synced 2024-11-19 20:08:28 +01:00
f999d94f4a
This change is the same as the one that introduced the options to
img2webp:
0825faa4 img2webp: add -sharp_yuv/-near_lossless
Change-Id: Id380d159299c38dd6440f833d487e00c0976afec
184 lines
6.3 KiB
Groff
184 lines
6.3 KiB
Groff
.\" Hey, EMACS: -*- nroff -*-
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.TH GIF2WEBP 1 "November 4, 2024"
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.SH NAME
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gif2webp \- Convert a GIF image to WebP
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.SH SYNOPSIS
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.B gif2webp
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.RI [ options ] " input_file.gif \-o output_file.webp
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.br
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.SH DESCRIPTION
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This manual page documents the
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.B gif2webp
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command.
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.PP
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\fBgif2webp\fP converts a GIF image to a WebP image.
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.SH OPTIONS
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The basic options are:
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.TP
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.BI \-o " string
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Specify the name of the output WebP file. If omitted, \fBgif2webp\fP will
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perform conversion but only report statistics.
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Using "\-" as output name will direct output to 'stdout'.
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.TP
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.BI \-\- " string
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Explicitly specify the input file. This option is useful if the input
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file starts with an '\-' for instance. This option must appear \fBlast\fP.
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Any other options afterward will be ignored. If the input file is "\-",
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the data will be read from \fIstdin\fP instead of a file.
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.TP
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.B \-h, \-help
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Usage information.
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.TP
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.B \-version
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Print the version number (as major.minor.revision) and exit.
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.TP
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.B \-lossy
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Encode the image using lossy compression.
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.TP
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.B \-mixed
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Mixed compression mode: optimize compression of the image by picking either
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lossy or lossless compression for each frame heuristically.
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.TP
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.BI \-near_lossless " int
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Specify the level of near\-lossless image preprocessing. This option adjusts
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pixel values to help compressibility, but has minimal impact on the visual
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quality. It triggers lossless compression mode automatically. The range is 0
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(maximum preprocessing) to 100 (no preprocessing, the default). The typical
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value is around 60. Note that lossy with \fB\-q 100\fP can at times yield
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better results.
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.TP
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.B \-sharp_yuv
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Use more accurate and sharper RGB->YUV conversion. Note that this process is
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slower than the default 'fast' RGB->YUV conversion.
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.TP
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.BI \-q " float
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Specify the compression factor for RGB channels between 0 and 100. The default
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is 75.
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.br
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In case of lossless compression (default), a small factor enables faster
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compression speed, but produces a larger file. Maximum compression is achieved
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by using a value of 100.
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.br
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In case of lossy compression (specified by the \-lossy option), a small factor
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produces a smaller file with lower quality. Best quality is achieved by using a
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value of 100.
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.TP
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.BI \-m " int
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Specify the compression method to use. This parameter controls the
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trade off between encoding speed and the compressed file size and quality.
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Possible values range from 0 to 6. Default value is 4.
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When higher values are used, the encoder will spend more time inspecting
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additional encoding possibilities and decide on the quality gain.
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Lower value can result is faster processing time at the expense of
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larger file size and lower compression quality.
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.TP
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.BI \-min_size
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Encode image to achieve smallest size. This disables key frame insertion and
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picks the dispose method resulting in the smallest output for each frame. It
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uses lossless compression by default, but can be combined with \-q, \-m,
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\-lossy or \-mixed options.
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.TP
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.BI \-kmin " int
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.TP
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.BI \-kmax " int
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Specify the minimum and maximum distance between consecutive key frames
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(independently decodable frames) in the output animation. The tool will insert
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some key frames into the output animation as needed so that this criteria is
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satisfied.
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.br
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A 'kmax' value of 0 will turn off insertion of key frames. A 'kmax' value of 1
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will result in all frames being key frames. 'kmin' value is not taken into
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account in both these special cases.
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Typical values are in the range 3 to 30. Default values are kmin = 9,
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kmax = 17 for lossless compression and kmin = 3, kmax = 5 for lossy compression.
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.br
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These two options are relevant only for animated images with large number of
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frames (>50).
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.br
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When lower values are used, more frames will be converted to key frames. This
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may lead to smaller number of frames required to decode a frame on average,
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thereby improving the decoding performance. But this may lead to slightly bigger
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file sizes.
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Higher values may lead to worse decoding performance, but smaller file sizes.
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.br
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Some restrictions:
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.br
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(i) kmin < kmax,
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.br
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(ii) kmin >= kmax / 2 + 1 and
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.br
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(iii) kmax - kmin <= 30.
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.br
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If any of these restrictions are not met, they will be enforced automatically.
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.TP
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.BI \-metadata " string
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A comma separated list of metadata to copy from the input to the output if
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present.
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Valid values: \fBall\fP, \fBnone\fP, \fBicc\fP, \fBxmp\fP.
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The default is \fBxmp\fP.
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.TP
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.BI \-f " int
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For lossy encoding only (specified by the \-lossy option). Specify the strength
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of the deblocking filter, between 0 (no filtering) and 100 (maximum filtering).
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A value of 0 will turn off any filtering. Higher value will increase the
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strength of the filtering process applied after decoding the picture. The higher
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the value the smoother the picture will appear. Typical values are usually in
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the range of 20 to 50.
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.TP
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.B \-mt
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Use multi-threading for encoding, if possible.
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.TP
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.B \-loop_compatibility
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If enabled, handle the loop information in a compatible fashion for Chrome
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version prior to M62 (inclusive) and Firefox.
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.TP
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.B \-v
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Print extra information.
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.TP
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.B \-quiet
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Do not print anything.
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.SH EXIT STATUS
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If there were no problems during execution, \fBgif2webp\fP exits with the value
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of the C constant \fBEXIT_SUCCESS\fP. This is usually zero.
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.PP
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If an error occurs, \fBgif2webp\fP exits with the value of the C constant
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\fBEXIT_FAILURE\fP. This is usually one.
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.SH EXAMPLES
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gif2webp picture.gif \-o picture.webp
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.br
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gif2webp \-q 70 picture.gif \-o picture.webp
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.br
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gif2webp \-lossy \-m 3 picture.gif \-o picture_lossy.webp
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.br
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gif2webp \-lossy \-f 50 picture.gif \-o picture.webp
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.br
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gif2webp \-q 70 \-o picture.webp \-\- \-\-\-picture.gif
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.br
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cat picture.gif | gif2webp \-o \- \-\- \- > output.webp
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.SH AUTHORS
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\fBgif2webp\fP is a part of libwebp and was written by the WebP team.
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.br
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The latest source tree is available at
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https://chromium.googlesource.com/webm/libwebp
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.PP
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This manual page was written by Urvang Joshi <urvang@google.com>, for the
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Debian project (and may be used by others).
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.SH REPORTING BUGS
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Please report all bugs to the issue tracker:
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https://issues.webmproject.org
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.br
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Patches welcome! See this page to get started:
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https://www.webmproject.org/code/contribute/submitting\-patches/
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.SH SEE ALSO
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.BR cwebp (1),
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.BR dwebp (1),
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.BR webpmux (1)
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.br
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Please refer to https://developers.google.com/speed/webp/ for additional
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information.
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