So I've written a small utility using qt5 to take advantage of the new --trim option Tobias has kindly added to xwallpaper.
Existing tools do not allow displaying geometry parameters from a picture display. Writing this in qt5 because I didn't want to reinvent more than I would need. I'd like to make this available so that fellow developers would help with providing aspect-ratio ready list for backgrounds. (As Tobias noted, not all aspect ratio are needed, since trim is "smart", but we still need basic "best picture area for cropping".... especially for portrait pictures, of which we have just a few in the basic collection)
aspect-crop-1.1.tgz
Description: aspect-crop-1.1.tgz