Make your signature transparent.

For ink on paper, a luminance threshold is more accurate than a segmentation model — it keeps thin pen strokes that AI models often eat. It is also instant. Honest engineering: the right tool, not the fanciest one.

Raise the sensitivity — Low keeps only the darkest ink, High also keeps lighter pen strokes. Even lighting when you photograph helps most.

No. Everything runs in your browser; the photo never leaves your device. For a signature, that matters.