The removal of the outside part of an image is called ‘Cropping.’ To have a perfect shape of an image, cropping is basically done. You can crop single photo as well as multiple photos together.

Learn more about Cropping:

Cropping (image) by Wikipedia

Crop Definition by Tech Terms

6 reasons to crop a photo by Digicam Help

See also:

Montage

Image Dimensions

Free Online Crop Tools:

Photo Cropper by Fotor

Lunapic