GIF2WEBP(1) General Commands Manual GIF2WEBP(1)NAME
gif2webp - Convert a GIF image to WebP
gif2webp [options] input_file.gif -o output_file.webp
This manual page documents the gif2webp command.
gif2webp converts a GIF image to a WebP image.
The basic options are:
Specify the name of the output WebP file. If omitted, gif2webp will perform conversion but only report statistics.
Print the version number (as major.minor.revision) and exit.
-lossy Encode the image using lossy compression.
Specify the compression factor for RGB channels between 0 and 100. The default is 75.
In case of lossless compression (default), a small factor enables faster compression speed, but produces a larger file. Maximum com-
pression is achieved by using a value of 100.
In case of lossy compression (specified by the -lossy option), a small factor produces a smaller file with lower quality. Best qual-
ity is achieved by using a value of 100.
-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.
-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.
-v Print extra information.
-quiet Do not print anything.
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/
gif2webp picture.gif -o picture.webp
gif2webp -q 70 picture.gif -o picture.webp
gif2webp -lossy -m 3 picture.gif -o picture_lossy.webp
gif2webp -lossy -f 50 picture.gif -o picture.webp
gif2webp was written by the WebP team.
The latest source tree is available at http://www.webmproject.org/code
This manual page was written by Urvang Joshi <firstname.lastname@example.org>, for the Debian project (and may be used by others).
SEE ALSO dwebp(1), cwebp(1), webpmux(1).
Please refer to http://developers.google.com/speed/webp/ for additional information.
February 01, 2013 GIF2WEBP(1)
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MINIDJVU(1) minidjvu-0.8 MINIDJVU(1)NAME
minidjvu - encode/decode black-and-white DjVu pages
minidjvu [options] input_file output_file
There is a similar syntax for multipage compression:
minidjvu [options] input_files output_file
See MULTIPAGE ENCODING section below for more details.
minidjvu encodes and decodes single-page black-and-white DjVu files.
minidjvu is derived from DjVuLibre, which is the primary support library for DjVu.
Besides bitonal DjVu, minidjvu understands Windows BMP, PBM and TIFF (through libtiff) formats. Both inputfile and outputfile may be BMP,
PBM, TIFF or DjVu. The file type is determined by extension. Input and output may coincide.
When given a DjVu-to-DjVu job, minidjvu decodes, then re-encodes the image. DjVu layers other than bitonal picture are lost.
Specifying a bitmap-to-bitmap job is possible, but relatively useful only with --smooth option.
All options preceded by two hyphens can be used with one hyphen. This is done to make minidjvu interface more familiar for DjVuLibre
To activate the multipage mode either specify in your command line more than just one input file, or pass to minidjvu a single multipage
tiff document. By default (if --indirect is not specified) the compressed pages are stored into a single bundled document under the name
provided in the command line.
There are several options referring to the multipage encoding process, namely --pages-per-dict, --indirect and --report.
Compute "average" representatives for shapes matching a pattern.
Sets aggression for pattern matching. The more the aggression, the less the file size, but the more likely substitution errors will
occur. The default is 100. Usually you can raise it to about 110 more or less safely. Probably even 200 will work fine, but don't
rely on that.
Consistent aggression levels between versions is not guaranteed. The default, however, will always be 100.
This option turns on --match automatically.
Remove small black marks that are probably noise. This algorithm can really devastate halftone patterns, so use with caution.
This option is turned on by --lossy.
Specify the resolution of an image, measured in dots per inch. The resolution affects some algorithms and it's recorded in DjVu and
BMP files (TIFF should join someday).
Sacrifice image quality to gain about 5-10% in file size. One erosion is almost invisible, but 10 erosions in a row spoil an image
badly (and they won't give you 50-100% of file size, alas). Erosion bonus stacks with pattern matching.
Erosion makes no sense when the output is not DjVu.
This option is turned on by --lossy.
Specifying this option in multipage mode causes minidjvu to generate an indirect multipage document, consisting from a single index
file, several single-page DjVu files (one per each image passed to the encoder) and several shared dictionary files. Note that the
index file is created under the name specified for the output file in the command line, while for each page the original input file
name is preserved, with the extension being changed to ".djvu".
This mode is useful for placing a large document to a Web server, or if you are going to postprocess the generated files (e. g. by
adding a color background). In the later case you may then want to convert your indirect document to DjVu bundled, using the djvmcvt
utility, supplied with DjVuLibre.
Turn on all lossy options. Is equivalent to --clean --erosion --match --smooth.
Run pattern matching. This is the main method of shrinking the file size, but it can also bring trouble with substitution errors.
Use --aggression option to maintain balance between file size and error probability.
This option is turned on by --lossy or --aggression.
Disable prototype searching. This makes lossless compression faster, but produced files become much bigger.
Specify how many pages to compress in one pass. The default is 10. If -p 0 is specified, minidjvu will attempt to process all pages
at once, but be aware that this can take a lot of memory, especially on large books.
Print verbose messages about what's done on which page. Works only with multipage encoding. Useful only to survive boredom while
compressing a book.
Flip some pixels that appear to be noise. The gain in file size is about 5%. Visually the image is slightly improved, but it's
Current filter is dumb and only removes black pixels with at least 3 white neighbors (of 4). You probably won't notice the effects.
This option is turned on by --lossy.
Print messages about various stages of the process. It's not very useful, but interesting to examine.
Specifies an extension for shared dictionary files (without a leading period). The default is "iff".
Do not disable libtiff warnings. By default, TIFF warnings are supressed. Under Windows default TIFF warning handler creates a mes-
sage box. This is unacceptable in a batch processing script, for instance. So the minidjvu default behavior is a workaround for
libtiff default behavior.
Multipage encoder does not work properly if pages have different resolution.
minidjvu-0.8 July 2009 MINIDJVU(1)