Resizing an image w.r.t to its height and width

问题

I need to resize an image so that if its height is smaller than its width, I'll set its height and vice versa. I wonder if there's a way doing this directly from the command line. Using '^' operator behaves just the opposite (or I could not succeed using it for my purpose). Thanks for replies.

来源：https://stackoverflow.com/questions/9003490/resizing-an-image-w-r-t-to-its-height-and-width