assemble the Aux data to heif request

[SpaceGrey]

Describe why it is important and where it will be useful

It seems that the library only supports decoding the aux data from the heif image, but no API for reverse. I want to add the gain map data to the image and haven't found a way to do so.

Describe your proposed solution

Not sure.

Describe alternatives you've considered, if relevant

No response

Additional context

No response

[bigcat88]

Good time of day. First it should be supported by libheif - only after it the support of this feature can be added here.