jxl-migrate-cli

jxl-migrate-cli is a Python 3 script to convert all applicable image files recursively in a folder to JPEG XL (JXL, image/jxl). It is based on kylxbn/jxl-migrate before it was rewritten to be a GUI program.

In case the conversion of an image is successful, the original image can be deleted and the JXL file will be all that's left.

Features

jxl-migrate-cli will try to do the following:

• Convert JPEG and JPG files into lossless transcoded or lossy JXL
• Convert PNG files into lossless JXL
• Convert APNG files into lossless JXL
• Convert lossless WebP into lossless or lossy JXL
• Convert lossy WebP into lossy JXL (-d 1)
• Convert GIF files into lossless or lossy animated JXL

The resulting JXL files will not be progressively encoded.

If desired, the original source image can be deleted automatically.

jxl-migrate also supports rudimentary error handling. In case it fails to convert a file because cjxl or dwebp did not do its job properly, then the source file will not be deleted even if you tell it to.

jxl-migrate will also report the before-and-after total filesizes along with a percentage of how much file space you saved by converting to JXL.

Requirements

jxl-migrate requires the following. All binaries should be added to the system's PATH environment variable so Python can run them.

• Python 3.x (tested working on 3.10.7)
• The webpinfo binary (to check if a WebP is lossless or lossy so that it can convert the file accordingly)
• The cjxl binary (to actually convert images)
• The dwebp binary (to decode WebP images into PNG images first because cjxl does not support WebP directly)

Usage

Just run the script on Python while providing the required parameters and it will process all images there recursively one by one. The images are processed in multiple threads (because of that, the output is quite hard to follow but I'm thinking of a way to improve that)

Valid arguments

python jxl-migrate-cli.py [directory] [--delete] [--lossyjpg] [--lossywebp] [--lossygif]

--delete: delete original source files if conversion succeeded (default FALSE)

--lossyjpg: convert JPEG files lossily (-d 1) (default FALSE)

--lossywebp: convert lossless WebP lossily (-d 1) (default FALSE)

--lossygif: convert GIF lossily (-d 1) (default FALSE)

--force-overwrite: perform conversion even if JXL file already exists

--jobs: number of jobs (cjxl processes) to use (defaults to CPU core count), e.g. --jobs=8

--cjxl-extra-args: Additional parameters to pass to jxl, e.g. --cjxl-extra-args="-e 8" to set cjxl effort to 8

Example

python jxl-migrate-cli.py /home/kylxbn/Photos --lossyjpg --delete

Disclaimer

While I did use this script to migrate my entire image folder and did not notice any issues, I still cannot guarantee that the error handling in this script is perfect and I can't help it if files get lost or damaged or anything. I cannot take responsibility for that. I did my best to avoid that, since I actually intend to use this script myself, but you never know.

The detection of file format is done purely by file extension (not case sensitive), so in case a file ends with (for example) .jpg but is not actually an image, then the script will be confused and try to convert it. However, cjxl should fail and the script should detect that. In that case, the original (impostor) .jpg file will not be deleted. At least that's how I intended it to function.

The script runs assuming you have all requirements satisfied and does not check if there are missing requirements. If a requirement is missing, the script might throw an error and crash. So make sure you have all requirements before running this script.

While I can't think of any bad reason (besides having a left-over PNG file converted from the original WebP with the original WebP file already deleted), cancelling the script by Ctrl+C or another way might be harmful and cause corrupted files. You have been warned.