Reducing Portrait to Basic Colors and Lines

[rich2005]

There is a standard Gimp filter in Filters -> Artistic -> Cartoon but it has been there a long time, there are better versions.

You could try the g'mic plugin http://www.gmic.eu which contains all sorts of effects. If you try it, read the instructions for a Windows install. You need to set up the correct path in Edit -> Preferences but one effect looks like this



edit:
A quick look around and an interesting procedure from Pat Davids blog.

https://patdavid.net/2014/09/woodcuthedc...ffect.html

It requires using a gmic filter, but nice resulting effect.