Straighten the converging lines you get when a camera is tilted up at a building, or flatten a document, whiteboard or artwork shot from an angle so it reads square on.
How the photo perspective corrector works
Upload the photo and say what should end up square, for example 'straighten the converging building verticals' or 'flatten this whiteboard so it reads square on'. Say whether the resulting edges should be filled or cropped. Run the tool and check that lines you expected to be parallel really are, and that any people in frame are not stretched. Reword and run again on the same upload if needed.
Tips for the best results
Name the lines that should be parallel or square, since that is what the correction locks onto. Strong perspective changes stretch things near the frame edge, so keep corrections moderate when people are in shot. Documents and flat artwork correct best because their edges are unambiguous.