I was generating logos for Git Notify’s Chrome Extension with the help of GoSpaces Tools. I have got a generic one in a decent sized banner. I had to crop off in the centre.
imagemagick to the rescue. but the args? A simple Google search solved it.
convert input.jpg -gravity center -crop 25x25+0+0 output.jpg
source: Image Magick Forum
Fred Weinhaus has put together lots of Image Magick scripts.
One I was looking was to crop in the middle is called squareup.
Look here if you want to generate your own logos