I made a tool called jxltran to do all kinds of operations on JXL files without touching the actual image data (no decode/re-encode), just by changing header fields. Also allows drawing splines on top of the image. Web version here: https://sneyers.info/jxltran/ (requires a browser that supports jxl).
Jon Sneyers
@jonsneyers@mastodon.social
I play with images at https://cloudinary.com For more info on me: http://www.sneyers.info
mastodon.social