I need to cut a large number of columns out of a PNG image. The area I want to remove is in the centre of the image; I therefore want the left and right edges to be closer together after the cut.
I can't find an obvious way of doing this in Gimp or Photoshop CS5 (I am very much a beginner). I would really like a tool which lets me say "cut out 100 columns, starting 4 pixels from the left". Any suggestions?