What do the parameters threshold, shaperate, and compactness mean and do?
The mathematical definitions of the parameters appear in the manual. In essence, threshold determines how large the segments get. Shaperate and compactness are weights that determine how the shapes look. Shaperate weighs the shape attributes versus the color attribute. Then within the shape calculation, the compactness rate weighs the compactness calculation over the smoothness calculation. The main thing to control: A lower shaperate will let the segments go out further to follow similar colors. A higher shaperate will generally keep segments closer in, albeit less spectrally homogenious.
