That is how it's generally used in graphics programs. However that doesn't change the fact that crop DOES mean "to cut off". Granted, most computer users would understand the meaning of 'crop' that is "mark an area and crop away anything not marked".
/ David Hedbor
Previous text:
2003-03-06 14:06: Subject: negative indices in array ranges
In all programs I use crop means keep selection.
/ Martin Nilsson (har bott i google)