The excellent Hugin application uses an image processing utility called hugin-tools.
Hugin-tools is available as a Debian package, which can easily be included as a dependency in a Debian package with “Depends: hugin-tools”. However I know of no way of including dependencies in a Flatpak. The only option is to recreate the whole thing in the manifest, which is a lot of work, a maintenance liability and probably beyond many people’s ability.
Would it be possible to create a module like those in ‘shared-modules’, which would perform the same function? Then including it would only need one statement in a manifest.
Most of the work for this has already been done - “hfiguiere” has already created a Flatpak for the whole of hugin https://github.com/flathub/net.sourceforge.Hugin/blob/master/net.sourceforge.Hugin.json
Rather than creating a module for the whole of hugin-tools. It might be better (and easier) to have the tools in separate modules
(note that this doesn’t work on Gnome Platform) “exalm” has done most of the work on what is needed for align-image-stack, the one I’m interested in https://github.com/Exalm/popout3d/tree/master/flatpak (note that this doesn’t work on Gnome Platforms later than 3.2)
If it’s possible, I think these tools would be very useful to authors of image-processing applications and align-image-stack would be a good one start with.