The Gimp provides the Rectangle, Ellipse and Lasso selection tools to help you cut out specific parts of a photo or illustration to keep, eliminate or edit. In addition, if you add an Alpha ...

Cut Out the Person Open the image including the person you want to copy by clicking the "File" menu and then choosing the "Open" option.

In the Gimp, you should be able to simply use the elliptical selection tool (E) to select the area you want, and then either copy and paste into another image, or Select->Invert (Ctrl+I) and then ...