[illiac786]

> iPhone HDR produces an HDR image file

What file format is this? iPhone produces tone mapped HEIC, yes, but that’s not HDR as you pointed out.

Or do you mean HDR video?

[astrange]

No, the HEIC has a proprietary attachment with the HDR data as well. You can see the iPhone display adapting when you view it in Photos.

[_aavaa_]

Do you have any info on how that attachment is stored/accesssed?

[illiac786]

I think I found it:

https://github.com/m13253/heif-hdrgainmap-decode

[_aavaa_]

Thanks! I'll take a look