Originally Posted by kovidgoyal
You should be able to re-use calibre code to update metadata/covers, that does not depend on OEB. There is no code in calibre to update existing jackets, just replace an old one with a new one.
Hmmm. Perhaps I wasn't looking at the right code then. I was looking at ebooks.oeb.transforms.cover.py, where it defines the cover templates and populates them in the insert_cover function()? I had thought I could reuse the template definitions, but that I would have to replicate all the remaining code of actual generation. As the insert_cover() function relies on self.oeb for the guide and manifest logic?
The jacket.py file in the same namespace also has dependencies on the oeb manifest from the Jacket class. The module level functions I could call, but again I think I would be replicating logic from the Jacket class.
Which is all fine if that is what you meant and recommend - but perhaps I am missing something more obvious