How to get a clean signature with a white background from a phone photo
Sign, photograph and clean up a signature so the paper is white and the ink is dark, then resize it to your form’s size and KB limit.
Why phone photos of signatures look grey
A phone camera sees white paper as light grey, often with a shadow from your hand or the phone. Forms want a clear dark signature on white, and grey paper also wastes KB because the compressor has to store the uneven shading. Cleaning it up makes the signature clearer and the file smaller.
Sign on the right paper
Use plain white paper with no lines and a black or dark blue pen that writes smoothly. Sign a little larger than usual so strokes are not too thin after resizing. Leave space around the signature.
Take the photo
Put the paper on a flat surface near a window in daylight. Hold the phone straight above the paper, not at an angle, and make sure your hand and phone don’t cast a shadow across the signature. Tap the screen to focus before you take the photo.
Clean it up
Open the signature resizer (/signature-resize/) and choose the photo. The tool evens out the lighting across the page, turns the paper white and the ink dark, and trims the empty space around the signature. The Ink threshold slider is set automatically; move it right to keep thin strokes, or left to make grey paper whiter. Tick Darker ink if the pen was light.
Set the size and KB
Enter the width and height and the KB limit from your form. Signatures compress well because they are mostly white, so they usually fit small limits such as 10 or 20 KB. Ready pages exist for /resize-signature-to-10kb/, /resize-signature-to-20kb/, /resize-signature-to-30kb/ and /resize-signature-to-50kb/.
JPG or PNG
The tool saves a JPG by default, which almost every form accepts. If your form accepts PNG, you can tick Save as PNG; PNG keeps edges crisp but the tool still checks it fits your KB limit. Use whatever format the form asks for.
Questions
How do I make my signature background white?
Photograph the signature on white paper in daylight, then open it in the signature resizer at /signature-resize/. It evens out the lighting, makes the paper white and the ink dark, and trims the edges automatically.
Why is my signature faint after cleanup?
The pen was probably light or the strokes thin. Move the Ink threshold slider to the right to keep thin strokes, or tick Darker ink; signing again with a darker pen also helps.
What size should a signature be for an online form?
Use the size your form’s instructions give, since it differs between organisations. Many forms ask for a wide, short image and a small KB limit such as 10–20 KB, but check your own advertisement.
Updated 2026-11-06