Computing global shape measures

Global shape measures are a convenient way to describe regions. They are generally simple and efficient to extract, and provide an easy means for high level tasks such as classification as well as helping direct low-level computer vision processes such as segmentation. In this chapter a large selection of global shape measures (some from the standard literature as well as other newer methods) are described and demonstrated

A Rectilinearity Measurement for Polygons

In this paper we define a function 7g(P) which is defined for any polygon P and which maps a given polygon P into a number from the interval (0, 1]. The number 7g(P) can be used as an estimate of the rectilinearity of P. The mapping 7(P) has the following desirable properties: - any polygon P has the estimated rectilinearity 7(P) which is a number from (0, 1]; - 7(P)=1 if and only if P is a rectilinear polygon, i.e., all interior angles of P belong to the set {,r/2, 3,r/2}; - inf 7(P) = 0, where H denotes the set of all polygons; PCH - a polygon's rectilinearity measure is invariant under similarity trans- formations