“200 DPI” doesn’t mean what the upload form checks
The IBPS advertisement describes the left thumb impression requirement as 240 × 240 pixels at 200 DPI. DPI (dots per inch) is a print-resolution figure — it tells a printer how many pixels to pack into each physical inch if the image is ever printed, and it’s stored as a small piece of metadata inside the file. It has no bearing on how many pixels the image actually contains, and critically, it is not what the upload form validates.
What the form actually checks, in practice, is the pixel grid (240 × 240) and the file size (20–50 KB). An image that is 240 × 240 pixels but tagged with the “wrong” DPI value in its metadata will upload and be accepted exactly the same as one tagged 200 DPI — because almost no web upload validator reads DPI metadata at all. This tool doesn’t write a DPI tag either way; it focuses on the two numbers that are actually enforced.
Capturing a usable thumb impression
A thumb impression is typically taken with ink on white paper, same as a signature, then scanned or photographed. Because the requirement is square (240 × 240) rather than the elongated shape of a signature, centre-cropping is more forgiving here — as long as the impression is reasonably centred in your source photo, the automatic crop this tool applies won’t cut into it.
As with the signature, a flat scan on plain white paper tends to compress more predictably into the 20–50 KB band than a phone photo with shadows or an off-white background — fewer stray details for the JPEG encoder to spend bytes on means a size that’s easier to land inside the required range on the first try.