algorithm for thinning

Please try this:

This is a morphological image processing. As an example of algorithm:
Iteratively delete (or erode) pixels inside the object (letter) to shrink it without shortening it or breaking it apart. Note that this is an iterative process. In general, you may stop the iteration after several times. Iterate it 3-5 times gives good and fast result.

You may find third party for this kind of image processing. The following thir party has that function.
http://www.artuxsoft.com[^]
http://www.artuxsoft.com/image-erosion.aspx[^]

Regards.

you can use distance transform(with chessborad distance metric,seems good.) first, then find the minimum distance points on the image which is will be the skeleton that you want. :)

see also this : http://homepages.inf.ed.ac.uk/rbf/HIPR2/distance.htm[^]

jkchan
http://cgmath.blogspot.com

Here is an overview See weather this help[^]

This will give an overview