Here is an early version of the HEIC / HEIF plugin.
Please test it with your photos and let us know how it works.
A big problem with HEIC is there are very few sample images, and NOTHING supports working on the file format so we cannot create our own images to try different things (e.g. rotation via EXIF, alpha channels, etc.).
I don't know why anyone would chose use this format right now, but Opus can view it even if nothing much else supports it. 
- DLL requires Opus 12.8.1 beta or above. It will not work with 12.8. You must install the beta released today (or a later version).
- DLL is 64-bit only. 32-bit builds will come later. I assume anyone who wants to test this is using 64-bit.
- It depends on Windows components for decoding HEIC. This seems to mean you need the HEVC and HEIC/HEIF codecs installed from the Microsoft Store. This probably requires Windows 10, although I am not sure.
- You can use the Windows Photos app to find out if the required components are installed on your computer. If they are, it will display an HEIC file. If they aren't, it will give you a link to the thing(s) you need to download. So try the Photos app if you see an error message in the Opus viewer for .heic files.
- Type
/home/Viewersinto the Opus location bar to find out where to copy the DLL, after extracting it from the zip file.
opuswic_opus12.8.1-beta-64bit.zip (95.8 KB)