Shape normalization through visible region center and unvisible region center

Abstract In this paper we present a new shape normalization method that is invariant to shape translation, rotation and scaling. We define a visible area density function and an unvisible area density function for a planar shape. Using these two functions we define a visible region center and an unvisible region center of the shape, respectively. When the visible and unvisible region centers of a shape locate at different positions they can be utilized as characteristic points to normalize the shape to a standard form. The normalizing process by use of the centers is presented. Experiments are executed on five groups of shapes with distortion of translation, rotation and scaling adding quantilization noise. The results show that the method is reasonable and available.