Exif support

[dbtsai]

Does it copy the exif and color space metadata to jpeg xl from the original input?

[olokelo]

Hi,
Unfortunately for now that's not the case.
You can see what's currently supported and what isn't in the table in the bottom of README.
I couldn't find any way to add Exif metadata from high level libjxl api.
I will be really grateful if someone smarter than me could figure out how to do it...

[dbtsai]

Just figure that out. Maybe it's possible to add exif/color profile metadata using exiftool after the jpeg xl file is created.

[olokelo]

Oh really! It appears to be working fine.
Mine ExifTool version is 12.26.
This adds tag "rights" with value "AAA" into containerized JXL file.

$ exiftool -rights="AAA" a.jxl

It's also possible to copy all tags from one image to another.
So probably that's a workaround for now but I really wanted to do that without external dependencies, it must be possible since cjxl does it but it's using entirely different api methods to do that.

[dbtsai]

Awesome. Good to know it's working.

I don't see that cjxl will handle those colorspace or metadata as it's purely a compression/decompression codec. ImageMagick internally also uses exiftool to handle those metadata as far as I know. For lossless compression, it will be very nice that you can have a mode to do bit-wise comparison with the original input image before deleting them.

[olokelo]

I mean AFAIK cjxl supports copying Exif and XMP tags from original input into jxl container.
It does that automatically if metadata is detected in source image.
I'm not a JPEG XL developer so I have little idea on how things work internally but I've been experimenting with it for a while.

[dbtsai]

Get it.

[alexjc]

Adding to this, you may need to use the -m flag so it adds the container if it's not present. For instance, I use this:

exiftool -m -artist="<PERSON>" -copyright="cc-by-nc-4.0 <ORGANIZATION>, 2022." -overwrite_original *.jxl

As for "copying from the original input", do you mean PIL Images in this case?
https://stackoverflow.com/questions/17042602/preserve-exif-data-of-image-with-pil-when-resizecreate-thumbnail