Streak and spot detection in digital pictures

A procedure is discussed for detecting dark streaks and spots (intensity anomalies) in a digital picture. The algorithm is insensitive to intensity cliffs and plateaux edges, and it can be finely `tuned¿ to accept anomalies of a given size while rejecting others. It has been successfully applied to the detection of scratches on the internal surfaces of hydraulics cylinders and results were presented in an earlier paper. The present article discusses the properties of the algorithm and demonstrates its behaviour on a test picture.