This is very slow. But if you wait long enough it will paint the NPR guy with a "Paint by numbers" effect. Colour spreads to adjacent pixels if they are similar in colour. Threshold determines how similar the pixels need to be for the colour to spread. Tether limits the spread by distance. If you'd like to change the picture: Scan your own 360x480 image and import into this project using: https://scratch.mit.edu/projects/66980580/
Check out the discussion forum "Non-photorealistic rendering projects" for other examples: https://scratch.mit.edu/discuss/topic/140162/
