This drawing algorithm is turning out to be much more complicated than I had first expected.

Imagine 10-15 colored pebbles laying on a sheet of paper in an orderly fashion. You're given a felt-tipped marker and are asked to group together all the blue pebbles by drawing circles and/or arcs. The result would look something like:



I'm now trying to do this programmatically. The code already knows where the blue ones are, where all the other ones are, etc., so there's no identification that needs to be done. But trying to code this behaviour is turning out to be rather frustrating.