High-quality polygonal contour approximation based on relaxation

An algorithm is proposed for extracting high quality, polygonal contours from connected objects in binary images. This is can be useful for OCR algorithms working on scanned text. It is also particularly interesting for raster-to-vector conversion of engineering drawings or other types of line drawings, where simple contours (known as Freeman chains) are grossly inadequate. Our algorithm is based on a relaxation technique, in which an initial polygonal approximation is iteratively refined until stability. Experiments demonstrate that this method consistently produces high quality results: the polygonal approximations obtained have a minimal number of corner points and remain extremely close to the original Freeman chain code.