Why this needs no model
A signature on paper is dark ink on light paper. The question for every pixel is simply whether it is ink or paper, and the answer is in its brightness. The page looks at the brightness of every pixel in the photo, finds the level that best separates the two groups, and makes everything brighter than that transparent.
A pixel near that level is made partly transparent rather than switched on or off, which keeps the curves of the pen stroke smooth instead of stepped. The result is cropped to the ink with a small margin, so it drops into a form or a document at the right size.
Using the signature
A cropped transparent PNG of a signature is usually a few kilobytes, well under the limits upload forms set.
| Use | Tip |
|---|---|
| Online forms asking for a signature upload | Check the size limit and the pixel dimensions the form states |
| PDFs and Word documents | Insert as a picture and set it to sit in front of the text |
| Email signatures | Export in black; blue ink can look like a link |
Limits
- Lined or patterned paper. The lines are dark enough to be read as ink; sign on plain paper.
- A signature over printed text, such as on a form. The printed text is kept too; sign on a blank sheet instead.
Questions people ask
- How do I take a good photo of my signature?
- Dark pen, plain white paper, daylight from a window, and the phone held flat above the page so the paper fills the frame. Keep the shadow of the phone off the signature.
- Why are parts of my signature broken or missing?
- The pen was light or the photo was bright, so some strokes are nearly as pale as the paper. Move the paper cut-off slider up until the strokes are whole.
- The corners of the paper show up grey.
- Uneven light makes the corners darker than the middle. Move the slider down until they disappear, or photograph again with the paper evenly lit.
- Is my signature uploaded?
- No. The page works on the pixels in your browser, with no model and no server. Nothing about your signature leaves the computer.
Other background jobs
- Remove white backgroundThe white box around a logo gone, the white inside it kept. No model.
- Transparent backgroundA PNG with a real alpha channel, for logos, products and stickers.
- Remove backgroundThe background off any picture, as a full-size transparent PNG.
- Passport photo backgroundPlain white or light blue behind an ID photo taken at home, with no shadow.