«Presets» are a common feature for several Colors commands. You can find its description in Sezione 8.1.1, «Caratteristiche comuni dei colori».

Standard deviation of gaussian neighborhood average for computing local contrast. If 0 is used a global threshold is used instead of one based on local contrast.

This sets a rough target of levels of accuracy for antialiasing, or set to 1 to disable antialiasing.

Thresholding level consists of two values. Change the lower threshold towards 0 to minimize shadows or towards 1.0 to minimize highlights. The high threshold decides the maximum values to include, above this it gets set to 0.

These are common features described in Sezione 8.1.1, «Caratteristiche comuni dei colori».