SignatureSmith / Signature background remover
Signature background remover
Turn a phone photo of your pen signature into a transparent PNG. Shadows evened out, paper removed, ink kept crisp, all on your device.
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How the background is removed
A signature photo is mostly paper with a thin line of ink, so its brightness histogram has two humps: a huge one near white and a small one in the dark. The remover measures every pixel's brightness, then finds the valley between the humps using Otsu's method, a thresholding technique published by Nobuyuki Otsu in 1979 that picks the cut-off separating two groups most cleanly.
Phone photos are rarely evenly lit. With “Even out shadows” on, the tool first estimates the paper's brightness across the page by blurring a small copy of the photo, then divides each pixel by that estimate. A shadow in one corner no longer looks like ink.
Pixels just around the cut-off become partly transparent (the “edge softness”), which keeps stroke edges smooth instead of jagged. Finally the empty margins are trimmed so the PNG is exactly the size of your signature.
Where to use a transparent signature
- PDFs: place it with Sign a PDF, or with Adobe Acrobat's Fill & Sign using the “image” option.
- Word and Google Docs: Insert › Image, then wrap text “in front of text”.
- Email signatures: resize to about 200 px wide before adding it in Gmail or Outlook settings.
- Letterheads and certificates: the transparent background sits cleanly on coloured paper.
Keep the transparent PNG of your real signature somewhere private. Anyone who has the file can paste it onto a document.
Background remover questions
How do I make my signature a transparent PNG?
Sign on plain white paper with a dark pen, photograph it flat in daylight, and choose the photo above. The remover drops the paper, keeps the ink and trims the margins. Press PNG to download it with a transparent background.
Is my signature photo uploaded?
No. The image is read and processed with your browser's canvas on your own device. There is no upload step and nothing is stored unless you press Save, which keeps a copy in this browser only.
Why is there grey noise around my signature?
Shadows or textured paper are darker than the cut-off. Drag the ink cut-off to the left until the noise disappears, keep “Even out shadows” switched on, and retake the photo without your phone's shadow over the paper if needed.
Parts of my signature disappeared. What do I do?
Light pen strokes are brighter than the cut-off. Drag it to the right, or re-sign with a darker pen such as a black gel pen or felt tip.
Can I change the ink colour?
Yes. Pick black, blue, navy, oxblood or our violet ink, or keep the original colours from the photo.
What is the best way to photograph a signature?
Use white printer paper, a black or dark blue pen, and even daylight from a window. Hold the phone directly above the page so the signature is not skewed, fill most of the frame with it, and avoid flash, which creates a bright hotspot.