Support HEIF images

[AndrewJDR]

These days, everybody is on iOS 11, and is thus probably sending messages in HEIF format rather than jpeg/png.

This means that image support in this bridge is largely broken at the moment. Unless there's some level of support in riot for displaying HEIF (I don't think so?), we'll need to convert the HEIF images to jpeg or png and attach those.

[michaelnew]

My bridge is running on High Sierra, and images seem to only show up in the filesystem as JPEG, not HEIF, even when taken and sent from an iOS 12 device. Are you able to check if images are actually coming through as HEIF and, if so, any ideas on why it could be different? I've been working on the media handling of the bridge lately and would like to fix this if possible, but so far haven't been able to duplicate it.

Apple makes it sound like anything iOS 11+ or High Sierra+ supports HEIF, but it sounds like images are sometimes quietly converted to JPEG when they're sent to other devices, and it's not very clear when that happens.

Side note: I would expect the same issues to be showing up for HEVC video, and I'm also not seeing that on my bridge.

[AndrewJDR]

In iOS, settings > camera >Formats > High Efficiency causes photos taken with the camera to be stored in heic/heif.

In terms of whether photos stored in heic/heif stay that way upon sending, I'm not sure on all the rules behind that. I can imagine that in order for it to send as heic, the photo needs to be stored as heic (of course), all the recipients in the thread need to be capable of opening heic (so imessage only, iOS devices only...)

[AndrewJDR]

It seems like it was (is?) possibly a bug in iOS/Messages causing heic to be sent over iMessage:
https://www.reddit.com/r/applehelp/comments/9sav9l/found_ios_1201_bugs_where_you_end_up_unknowingly/

So hopefully, this was just a case of me observing the bug, and hopefully that bug has been fixed since then. That would at least explain both of our observations...

[sabogalc]

itsjunetime/smserver#105