How to describe pure form and how to measure differences in shapes using shape numbers

Surface trees – Representation of boundary surfaces using a tree descriptor

“…The initial inward transition may be chosen in such a way that it is maximally aligned to the major axis used in the computation of the eccentricity of the solid [12]. This major axis can be determined as the segment of line between the centers of the two faces in the surface furthest apart.…”

The Use of Contour, Shape and Form in an Integrated Neural Approach for Object Recognition

“…Another interesting method for 2D invariant object representation is the use of the compactness measure of a shape, sometimes called the shape factor, and which is a numerical quantity representing the degree to which a shape is compact. Relevant work in this area within the theory of shape numbers was proposed by Bribiesca and Guzman (Bribiesca and Guzman, 1980). Worthington studied topographical information from image intensity data in grey scale using the Shape from Shading (SFS) algorithm (Worthington and Hancock, 2001).…”

Multi-Sensor Scene Synthesis and Analysis

“…Fourier desc,'iptors [3], chain codes [51,52], graph representation (of which strings and trees are special cases) [50], and shape nimbers [123,124]. Variatioiis and inconsistencies in shape are handled by the use of models [53], "rubber masks" [122], relaxation [54], and syntactic nniques [50].…”