Perspective crop

I'd like to suggest a "perspective crop" and/or "perspective correction" option (example). After drawing a rectangle on the image, the user can move any of the four corners independently to produce a quadrilateral.

• Perspective correction "squares" the angles of the quadrilateral to produce a rectangle, hence correcting the perspective of the image.
• Perspective crop is the same as above, but also crops to the rectangle.
• Be useful if holding down Alt, Ctrl, Shift keys, lets the use move pairs of corners together