How to Scan Your Signature for Online Exam Forms (Under 20 KB)

Almost every online application in Nepal — Lok Sewa, university admissions, bank recruitment, licence renewals — asks for a scanned handwritten signature, and almost every portal enforces the same trio of rules: black ink on a white background, clean edges, and a file size typically capped at 20 KB. A signature photographed casually on a desk fails all three: the paper reads grey, shadows fill the letter loops, and the raw photo weighs hundreds of kilobytes. The fix is a process called thresholding, and you can do it in about two minutes with any phone and a browser.

Step 1 — Set up the perfect signature shot

The quality of the final scan is decided before any software touches the file. Sign with a black or dark blue gel pen (0.7 mm or thicker) on plain white unlined paper. Keep the signature at your natural size — roughly 6 to 10 cm wide — and sign once, confidently; hesitant strokes show up as broken lines after thresholding. Then place the paper under even light near a window or under two room lights from opposite sides so no shadow crosses the ink, and photograph it straight from above with the signature filling most of the frame. Tap to focus on the ink and, if your camera app allows, lock the exposure slightly down so the paper stays bright white instead of blowing out.

Step 2 — Threshold-scan it in the browser

Upload the photo to the Exam Signature Scanner and use the Paper Whitening Threshold slider. The tool maps every pixel brighter than the threshold to pure white (#FFFFFF) and every darker pixel to solid ink, which is exactly the transformation an exam-portal validator applies internally when it checks whether your signature reads cleanly. Move the slider until the background snaps to white with no grey patches, while the strokes stay continuous and unbroken. If strokes develop gaps, the threshold is too high; if the paper turns grey and muddy, it is too low. The live preview updates as you drag, so finding the sweet spot takes a few seconds.

Step 3 — Export under 20 KB with the right dimensions

Crop away the empty paper margin — portals compare the ink-to-whitespace ratio, and a tiny signature floating in a large white box is flagged as low quality. A final canvas between 300×100 and 600×200 pixels preserves the natural aspect ratio of a signature. Choose the 20 KB ceiling and let the engine iterate quality and dimensions until the export fits; because thresholded images are essentially two colours, they compress extremely well and the result usually lands between 5 and 15 KB. Export as PNG if the portal accepts it (sharper edges) or JPEG when JPEG-only is stated.

Why portals reject signatures

• Grey or shadowed background — the scanner validator reads the paper as noise; re-run with a higher whitening threshold.
• Broken or faint strokes — the threshold ate thin ink; sign with a darker pen or lower the threshold slightly.
• Oversized file — the raw photo was uploaded unchanged; always pass through the KB-ceiling export.
• Wrong aspect ratio — a tall crop around a wide signature looks distorted; keep the natural proportions.
• Mismatch with admit card — sign the way you will sign in front of the exam invigilator; identical-looking signatures avoid verification queries.

The draw-pad alternative

If you cannot get a clean photo — damaged paper, shaky hands, no good light — use the built-in draw pad instead. On a phone, sign with a stylus or finger in landscape orientation for natural wrist movement; on a laptop, use a mouse with slow, deliberate strokes and let the stroke-smoothing setting round the jitter. The draw pad exports through the same whitening and 20 KB pipeline, so the result is indistinguishable from a scanned one.

Threshold behaviour and KB ceilings reflect portal requirements commonly published in official vacancy notices as of October 2026. Individual portals may differ — verify against the notice you are applying to. Job Finder is an independent educational resource.