Resize a signature image

Sign with a black or dark blue pen on plain white, unlined paper, and make the signature large; a big signature scaled down looks crisp, a tiny one scaled up looks ragged. Lay the paper flat near a window, hold the phone directly above it so the sheet is not skewed, and keep your own shadow off the page. Fill most of the picture with the signature before you press the button.

Forms commonly allow only 10 to 50 KB for a signature, because it is stored next to thousands of others and printed small. A few dark strokes on white compress extremely well, so reaching such a limit seldom costs visible quality. If the form sets a minimum that a clean signature falls below, the file is padded up to it without altering the image.

When a limit is given as "less than 20 KB", enter 20 as the maximum and leave the minimum empty. When it is "between 10 and 20 KB", fill in both.

Phone cameras tend to render white paper as pale grey or yellow. Switching on "Replace the background" is meant for portraits and may not separate thin pen strokes cleanly, so for signatures it is better to fix the picture at the source: more light, no flash glare, and the paper filling the frame. A JPG of dark ink on evenly lit paper is what reviewers expect to see.