A Min-Max Medial Axis Transformation

Blum’s medial axis transformation (MAT) of the set S of l's in a binary picture can be defined by an iterative shrinking and reexpanding process which detects “comners” on the contours ofconstant distance from S, and thereby yields a “skeleton” of S. For unsegmented (gray level) pictures, one can use an analogous definition, in which local MIN and MAX operations play the roles of shrinking and expanding, to compute a “MMMAT value” at each point of the picture. The set of points having high values defines a good “skeleton” for the set of high-gray level points in the given picture.