Fit best straight lines and arcs to 2D points

A colection of points is measured by scanning a 2D shape. I need these points to be reduced to a series of straight lines and arcs. The tolerance, ie the maximum distance any of the points is away from the calculated lines, should be an input parameter for the program. The program needs to be either in Delphi or it should be a DLL which Delphi can use.