A while back got curious about the approach used by apps like Manga Camera ( https://play.google.com/store/apps/details?id=jp.co.supersof... ) to turn photos into Manga style "drawings".

Turns out there's a paper on it "MANGAWALL: GENERATING MANGA PAGES FOR REAL-TIME APPLICATIONS" ( https://www.semanticscholar.org/paper/MangaWall-Generating-m... ) and an implementation - https://github.com/zippon/MangaWall - that implementation uses ordered dithering ( https://github.com/zippon/MangaWall/blob/master/src/MangaEng... ) among other things to help produce a pencil drawn like effect.

Anyway just saying ;) To me at least, pretty fascinating ...