User blog comment:FlyingSquirrel192/Taking pictures on a laptop/@comment-3514063-20110821015552/@comment-2194058-20110821021356

There's a tool that does that. If you look for the dotted box, you can click and drag the cutting tool to focus on the important part. Once you've chosen what you want to focus on, copy it with the right-click button and start a new page, or erase the page. Paste the newly copied image and save it.