Smoothing in a tangential direction of a contour and detail enhancement in its perpendicular direction are simultaneously achieved with spatial filters having prescribed weighing factor distribution. An area including a contour is first designated, and a direction of the contour is detected. A weighted...http://www.google.co.uk/patents/US5050227?utm_source=gb-gplus-sharePatent US5050227 - Method of and apparatus for image smoothing along a tangential direction of a contour
