Pattern recognition of basic shapes in Rev

[David Bovill]

I'd like to emulate the behavior of some software which allows you to draw
rough shapes by hand and recognises whether you want to draw a circle,
triangle, rectangle etc. The tools would allow you to use the freehand pen
polygon tool to sketch and then replace the sketch with an appropriately
placed polygon or button.

The missing algorithm is one which will take an arbitrary set of poygon
points and return the recognised shape and vertices / dimensions. Any ideas
where to start?