The angle-of-sight signature for two-dimensional shape analysis of manufactured objects

摘要

A new two-dimensional (2D) shape-encoding scheme is introduced which is based on the idea of the angle-of-sight (AOS). Using this scheme, a shape can be efficiently transformed into a one-dimensional (1D) signature by recording the AOS vs. distance of each boundary point with respect to a shape-specific chord-of-sight (COS). The COS is selected by using an extension of the notion of shape boundary, to the idea of shape-specific points and the characteristic ellipse (CE). The AOS signature has many important properties including: it is information-preserving and thus unique, it does not require boundary smoothing; it has its own selectable smoothing property; it can provide a set of multi-scale representations by means of a simple operation; it is transformation-invariant; it is defined at all points; it preserves symmetries. As well, for matching purposes, a two-level matching process is proposed using a global measure (the eccentricity of the CE of a shape) and a dissimilarity measure based on the AOS signature. The encoding and matching techniques developed have been tested with 35 manufactured objects. The results obtained show that the AOS signature and the two-level-matching technique are quite effective and reliable for the recognition of 2D shapes of typical manufactured objects.