Thinning out lines?

[gramp]

There is also an interest in the general case of "thinning regions to their central lines". The central line can be guessed at by selecting the region and "shrinking" to smaller and smaller selections, but the process doesn't care anything about preserving single pixels in a line.

I was trying to find out more about it a few days ago:
https://stackoverflow.com/questions/6955...ong-region
which references this project (which then discusses Hilditch's Algorithm):
http://cgm.cs.mcgill.ca/~godfried/teachi...tml#define

A skeletonizing tool would be useful for finding the centerlines for later stroking, to replace a rough area with a smoother one.