[jama_]

Actually, in my recent vibe coding adventures I tested making a ProRAW converter app that also applied the included gain map to the image and encoded via libjxl on device. Surprisingly, Photos.app was able to display the converted image with HDR, but the HDR tag in the UI is only displayed for images with the proprietary gain map.

There seems to be some support there, though I tested on iOS 26.

[jiggawatts]

Yes, but you can't send that to anyone via iMessage. It corrupts the image.

[jama_]

That I of course didn't test. Yeah, I'd expect them reencoding images to save on bandwidth, and they're probably doing so naively for JXL (maybe even converting to HEIC).