[Atle Richter schie]

A solution would be to open Adobe Bridge, navigate to the folder with your images, go to View -> Sort -> By dimensions. Then Bridge will sort your images by pixel-size.

Next up, find the “break point” in size where you’ll start upsizing instead of downsizing and just batch process the ones above.

(The Image Processor (for Photoshop) in Bridge is located in Tools -> Photoshop -> …)

[Atle Richter schie]

I might be missing something, but could this be solved with actions and the “trim” + “canvas size” functions? At least if the product images are on white/isolated background trim could remove excess pixels, and then redefine the amount of whitespace needed for the differens proportions with canvas size.