Registration portals routinely ask for three uploads: a photo, an ID scan, and your signature as a separate image — often with tight rules like "JPG, white background, 10–20 KB, 140 × 60 px". Here's how to produce that without a scanner.

Step 1: Capture It Properly

  • Sign with a black or dark blue pen on plain white paper. Thin ballpoint lines can disappear after compression — a gel or fine marker pen reads better.
  • Sign larger than you normally would. More pixels of ink survive the downscale.
  • Photograph it straight from above in even, indirect light. Avoid the shadow of your phone falling across the paper, and never use flash on glossy paper.

Step 2: Crop Tight, Then Straighten

Crop to just the signature with a small, even margin — portals validate aspect ratio, and a page full of empty paper wastes your pixel budget. If the paper was slightly rotated, straighten it so the baseline is level.

Step 3: Clean the Background

Photos of white paper come out grey or cream. Two paths:

  • White background required (most portals): remove the off-white cast so the paper reads as pure white while the ink stays dark. A color-based background remover set to sample the paper tone, with the replacement set to solid white, does exactly this.
  • Transparent PNG (for putting the signature onto contracts or PDFs): same removal, but keep the background transparent. Then the signature can sit on any document without a white box covering the text beneath it.

Keep the ink itself untouched — over-aggressive tolerance settings eat thin strokes and leave a broken signature.

Step 4: Hit the Size and Weight Limits

Two independent constraints:

  • Dimensions: resize to the stated pixel size (commonly 140 × 60 px for signatures — small, which is why a tight crop matters).
  • File size: many portals demand 10–20 KB. Rather than guessing quality values, compress to a target size so the file lands just under the ceiling at the best quality that fits. If a signature is too heavy even at low quality, the cause is usually a noisy photo background — clean it first, then compress.

Two Practical Warnings

  • Format matters: if the form says JPG, don't upload a renamed PNG. Convert properly.
  • Keep the signature file private. A signature image is a sensitive asset — process it with tools that work locally in your browser rather than uploading it to a random online service, and delete stray copies from your Downloads folder when you're done.