How & when to use this
Whiteboard & document photos
Shot a whiteboard or paper at an angle? Drag the 4 corners to the document's edges and the tool warps it to a straight rectangle — like a mobile scanner, right in your browser.
Architectural photography
Buildings shot from below look like they're leaning back. Place the 4 corners on the building's corners and correct the keystoning without any desktop software.
Receipts & business cards
Drag corners to the receipt edges, hit Correct — you get a clean overhead view, great for archiving or reading text that was hard to see at an angle.
How the warp works
Uses a projective transform (homography) computed from your 4-point selection. The output maps those corners to a flat rectangle using bilinear interpolation on the Canvas API. Zero server, zero upload.