Why 20KB is hard
Signature fields on exam and job portals often allow only 20KB. A phone photo is hundreds of times larger, so you need to crop and compress in a careful order.
Step 1: write and photograph it
Sign on plain white paper with a dark pen. Take the photo in daylight, straight from above, with no shadows.
Step 2: crop tightly
Cut away all the empty paper so the signature fills the frame. Fewer pixels means a smaller, sharper result.
Step 3: compress
Use the 20KB compressor. Dark ink on white compresses very well and stays readable.
If the portal also needs exact pixels
Some forms want a size like 140 × 60 px. Set it with the resize tool first, then compress.