“Presets” are a common feature for several Colors commands. You can find its description in 第 8.1.1 节 “Colors Common Features”.

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 第 8.1.1 节 “Colors Common Features”.