For G'MIC 2.9.8 and later, don't use this but use "Filters -> G'MIC-Qt -> Artistic -> Comic Book" (You have to have updated G'MIC filters by "ctrl-R"). For GIMP 2.8 ...

GIMP, which stands for GNU Image Manipulation Program, is a popular open-source graphics editing software available for free. With GIMP, you can create stunning visuals and animations, including ...

For some reason the auto Github generated source code of this filter is outdated. So please use the updated source code I provided here named photo_2_cartoon_source ...