Get Camera Roll pictures from BackUp? How?

Before we traded a iPhone 4s in, I backed it up. I do not want to restore it, but I do want to get the photos from the Camera Roll to my Mac. Either through iphoto, etc. Can I do this? I backed the phone up to the computer and the cloud. Again, I do not have a iphone that I want to restore this info to. I only need to get the pictures from the Camera Roll to iphoto. I have seen apps that say they extract photos... if this the only way? It seems with a back up on the same computer I should be able 'import' them.