I'd also like to be able to pick a part of the image to focus on, e.g.
if the image is a portrait of a person I could pick their face.
Idealy I'l like a piece of software which would present me with the
images one at a time and let me draw a bounding box (with a fixed
ratio I specify in advance) around the area of the image I want. Then
I'd like it to generate a thumbnail.
Better yet, I'd like it to spit out the filename and the co-ordinates
of opposite corners of the bounding box on the command line so I can
pipe it into a script and scale the image on my own terms.