Colored pencil filter internals

I frequently use the ‘Colored pencil’ filter in GIMP, and would like to understand how it works, with a mind to achieving similar results from the command-line. However, I’ve been unable to figure out where it’s implemented. Can anyone point me to the right place in the source code to get started?

Kind Regards,
Mike

@Michael_Gauland Welcome to the forum! In GIMP, you can create a new layer from the filter with the command and parameters as the layer name. This can be selected in the G’MIC plugin window.