I am using Gigapixel AI alongside the stock Photos app on a Mac.
Alas, it seems there is no extension for the Photos App to allow in-app processing. This would be awesome, but I do understand your users probably skew towards a user base who use other products.
However, this meant I was dragging and dropping from Photos into Gigapixel. After a while, I noticed that for all but the smallest images, Gigapixel was only loading a reduced size file (maxing out at about 1000px longest dimension).
I thought this may be behaviour of the drag and drop function in OSX / Photos but a drag to the Finder or to Final Cut Pro seems to drop a full size image.
Is anyone aware of why this happens? I can exporting first (or dragging and dropping to the Finder first) but this makes the workflow clunkier than it needs to be.
Also if there was thought of a Photos plugin that would be great to hear.