Signature extractor — clean, crop and resize a signature photo

How to use Signature Extractor & Resizer

1. Choose a photo or scan of your signature on white paper.
2. Leave Ink detection on Automatic. Switch to Manual and move the Threshold slider only if the result looks wrong.
3. Pick an Ink colour: Black, Blue or Keep original.
4. Choose a Background: Transparent PNG for documents, White JPEG for upload forms.
5. Set the Margin around the signature, and if a form gives limits, fill in Width, Height and Maximum size (0 means no limit).
6. Press Extract signature and download the file ending in -signature.

What it does and when to use it

A photo of a signature carries a lot of baggage: grey paper, shadows, the edge of the desk, and far too many pixels. Forms want something much simpler, just the ink, cropped close, at a fixed size and under a small file limit.

Use it to:

• Sign letters and PDFs with a transparent PNG that sits cleanly on the page.
• Meet portal rules for exam, job and bank applications that ask for a signature image of a set size and KB range.
• Recolour faded ink to solid black or blue so it prints and scans clearly.
• Tidy a scan that has a grey background or a pencil line through it.

For a specific exam or ID form, ToolsRift also has ready-made pages, such as the SSC Signature Resizer, the IBPS Photo & Signature Resizer and the PAN Card Photo & Signature Resizer. They fill in the official numbers for you.

How it works

All steps run in your browser.

1. Light versus dark. The image is turned into brightness values. In Automatic mode the tool uses Otsu’s method, a classic way to find the brightness level that best splits a picture into two groups (ink and paper), and then nudges it slightly towards lighter strokes.
2. Lifting the ink. Pixels darker than the threshold become ink, with a soft edge so curves stay smooth instead of jagged. Everything lighter becomes transparent.
3. Recolouring. Ink pixels are painted solid black or blue, or keep their own colour.
4. Cropping. The tool finds the box around the ink and crops to it, plus the margin you chose (a percentage of the signature’s longer side).
5. Sizing. With width and height set, the signature is fitted inside that exact box. With only one set, the other side follows the signature’s proportions.
6. File size. With a maximum KB set, the tool searches for the best quality that fits. If you left both pixel boxes at 0, it may also scale the signature down to meet the limit.

Worked examples

A signature for a bank form: 140 × 60 px, white, under 20 KB. Choose White JPEG, type 140 and 60, and set 20 KB. Say the ink, with its margin, measures about 900 × 300 px. Fitted into 140 × 60, it becomes 140 × 47 px, with white bands above and below so nothing is cut. A file this small is normally well inside 20 KB.

A transparent signature for a cover letter. Keep Transparent PNG, Black ink and both sizes at 0. You get the signature at its photographed size with the paper removed, ready to place on a document.

Faint blue ballpoint on cream paper. Automatic mode may drop the lightest strokes. Switch to Manual and raise the threshold a little at a time until the full signature appears, then set the ink to Blue so the strokes are solid.

Limits and tips

• Plain paper only. Lined, squared or printed paper leaves marks that look like ink. Sign on a blank sheet.
• Shadows become ink. A dark shadow across the page can be picked up as a smudge. Re-take the photo in even light rather than fighting it with the slider.
• Colour is replaced, not detected. Black or Blue paints every ink pixel one colour. Choose Keep original if a form wants the real pen colour.
• Fixed sizes add margins. If a form fixes both pixel dimensions, expect white or transparent padding on two sides.
• Too-small limits. If the maximum KB cannot be met at the size you typed, the tool says so. Try smaller dimensions or a White JPEG, which compresses better than PNG.
• Check the form’s own rules for pen colour, size and file type before you upload.