ZigZag

Window 30 px

How far ZigZag looks around each pixel to judge the local lighting. Lower it for fine print, raise it for large text or broad shadows.

Background 90 %

How bright a pixel must be, next to its neighbours, to be treated as background. Lower it to about 60 % to rescue faint ink on degraded documents.

Ink 0

Nudges the automatic threshold. Positive keeps more ink — bolder, but noisier; negative cleans harder at the risk of thinning strokes.