cjxl - Man Page

• Convert an image to JPEG XL: cjxl path/to/image.ext path/to/output.jxl
• Set quality to lossless and maximize compression of the resulting image: cjxl --distance 0 --effort 9 path/to/image.ext path/to/output.jxl
• Display an extremely detailed help page: cjxl --help --verbose --verbose --verbose --verbose

tldr.sh

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

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

-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.

-e effort, --effort=effort

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.

Recognized effort settings, from fastest to slowest, are:

• 1 or “lightning”
• 2 or “thunder”
• 3 or “falcon”
• 4 or “cheetah”
• 5 or “hare”
• 6 or “wombat”
• 7 or “squirrel” (default)
• 8 or “kitten”
• 9 or “tortoise”

# 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

djxl(1)

djxl(1).