cjxl.txt 2.77 KB
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cjxl(1)
=======
:doctype: manpage

Name
----

cjxl - compress images to JPEG XL

Synopsis
--------

*cjxl* ['options'...] 'input' ['output.jxl']

Description
-----------

`cjxl` compresses an image or animation to the JPEG XL format. It is intended to
spare users the trouble of determining a set of optimal parameters for each
individual image. Instead, for a given target quality, it should provide
consistent visual results across various kinds of images. The defaults have been
chosen to be sensible, so that the following commands should give satisfactory
results in most cases:

----
cjxl input.png output.jxl
cjxl input.jpg output.jxl
cjxl input.gif output.jxl
----

Options
-------

-h::
--help::
    Displays the options that `cjxl` supports. On its own, it will only show
    basic options. It can be combined with `-v` or `-v -v` to show increasingly
    advanced options as well.

-v::
--verbose::
    Increases verbosity. Can be repeated to increase it further, and also
    applies to `--help`.

-d 'distance'::
--distance='distance'::
    The preferred way to specify quality. It is specified in multiples of a
    just-noticeable difference. That is, `-d 0` is mathematically lossless,
    `-d 1` should be visually lossless, and higher distances yield denser and
    denser files with lower and lower fidelity. Lossy sources such as JPEG and
    GIF files are compressed losslessly by default, and in the case of JPEG
    files specifically, the original JPEG can then be reconstructed bit-for-bit.
    For lossless sources, `-d 1` is the default.

-q 'quality'::
--quality='quality'::
    Alternative way to indicate the desired quality. 100 is lossless and lower
    values yield smaller files. There is no lower bound to this quality
    parameter, but positive values should approximately match the quality
    setting of libjpeg.

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-e 'effort'::
--effort='effort'::
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    Controls the amount of effort that goes into producing an ``optimal'' file
    in terms of quality/size. That is to say, all other parameters being equal,
    a higher effort should yield a file that is at least as dense and possibly
    denser, and with at least as high and possibly higher quality.
+
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Recognized effort settings, from fastest to slowest, are:
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- 3 or ``falcon''
- 4 or ``cheetah''
- 5 or ``hare''
- 6 or ``wombat''
- 7 or ``squirrel'' (default)
- 8 or ``kitten''
- 9 or ``tortoise''

Examples
--------

----
# Compress a PNG file to a high-quality JPEG XL version.
$ cjxl input.png output.jxl

# Compress it at a slightly lower quality, appropriate for web use.
$ cjxl -d 2 input.png output.jxl

# Compress it losslessly. These are equivalent.
$ cjxl -d 0   input.png lossless.jxl
$ cjxl -q 100 input.png lossless.jxl

# Compress a JPEG file losslessly.
$ cjxl input.jpeg lossless-jpeg.jxl
----

See also
--------

*djxl*(1)