makejxl

This tool will bulk encode image files in given directory to JPEG-XL. It will leave original files intact, creating .jxl file next to each original.

JPEG-XL encoder is still under development, but format is frozen since 2020-12-24 and files encoded today will be readable by later versions of decoders.

You don't need to use this tool at all. Examples for Shell and PowerShell scripts are below.

Supported input file formats:

.jpeg/.jpg (conversion is lossless and reversible)
.exr
.gif
.pfm
.pgm/.ppm
.pgx
.png

Supports Windows, Linux, MacOS and probably other OSes.

Linux

pip install makejxl
makejxl --recursive /home/username/myphotos

You will need cjxl in path. You can get it by running build_cjxl.sh as root

Or simpler alternative that doesn't need this script:

apt install imagemagick parallel
find /path/to/images -type f -iregex '.*\(gif\|jpe?g\|png\)$' | parallel convert {} {.}.jxl

Windows

You can download and use it as single Windows binary, see Releases

Unfortunately antiviruses don't like packed Python executables, so expect false positives from them if you go this way. Best way is pip.

You will need cjxl in path. It's best to build it using this tool and copy to %USERPROFILE%\AppData\Local\Microsoft\WindowsApps

./makejxl.exe "c:\\Users\\username\\Pictures\\My Vacation"

Or simpler alternative that doesn't need this script:

cd c:\photos
Get-ChildItem -Path c:\temp\ -File -Include '*.jpg', '*.jpeg' -Name | Foreach {cjxl $_ $([io.path]::ChangeExtension($_, "jxl"))}

TODO

Decoder mode