Unable to read/write Exif metadata

[Disty0]

For reference, i am currently trying to implement JPEG XL support on a stable diffusion webui: vladmandic/automatic#3600
But i am unable to save and read exif metadata.

The line for generating the exif metadata:

exif = piexif.dump({ "Exif": { piexif.ExifIFD.UserComment: piexif.helper.UserComment.dump(exifinfo, encoding="unicode") } })

Added a print to this plugin's save function to see if it gets the exif metadata like this:

And it definitely gets the exif metadata so i am guessing this issue is on the rust backend:

Saved images has "something" as exif in them:

But nothing is able to read the exif metadata in the saved images:

I also have JXL images that has valid exif metadata in them (converted from jpg to jxl with imagemagick) but plugin is still unable to read the exif metadata.

[Isotr0py]

But nothing is able to read the exif metadata in the saved images.

Oh, that's because I set compress=True by default when encoding jxl image with metadata. However, many software (including exiftool and exiv2) can't recognize the compressed exif data. I have opened #87 to make it optional and disabled by default.

I also have JXL images that has valid exif metadata in them (converted from jpg to jxl with imagemagick) but plugin is still unable to read the exif metadata.

This plugin can't decode jxl images with exif data directly, because upstream jpegxl-rs doesn't have high-level API for this.

However, if a jxl image is created from jpeg reconstruction, the exif metadata should be handled correctly, because we will reconstruct jxl to jpeg in this plugin instead of directly decoding, which means we will return an JPEG PIL instance. So I guess the jpg->jxl convert in imagemagick is using direct encoding instead of lossless jpeg reconstruction.

BTW, if you use the official cjxl tool provided by libjxl to convert jxl from jpg, this plugin should be able to read the image with exif metadata. (This is also how I create sample jxl image with metadata for test)

[Isotr0py]

BTW, you can try to use the pre-release wheels from main branch: https://github.com/Isotr0py/pillow-jpegxl-plugin/releases/tag/exif-dev. These wheels should be able to encode image with exif metadata compatiable with exiv2 and exiftool.

[Disty0]

BTW, you can try to use the pre-release wheels from main branch: https://github.com/Isotr0py/pillow-jpegxl-plugin/releases/tag/exif-dev. These wheels should be able to encode image with exif metadata compatiable with exiv2 and exiftool.

Pre-release wheels fixed the metadata saving:

So I guess the jpg->jxl convert in imagemagick is using direct encoding instead of lossless jpeg reconstruction.

That is true. imagemagick still treats it as a png with -quality 100 instead of using jpeg reconstruction.

This plugin can't decode jxl images with exif data directly, because upstream jpegxl-rs doesn't have high-level API for this.

Saving is working with the pre-release wheels, so only this upstream issue remains right now.