Grouping Symmetrical Structures for Object Segmentation and Description

A method is presented for segmenting gray-value images into objects (or their parts) and for recognizing the detected objects. Starting from edge maps, the method extracts axial descriptions of symmetrical shapes. Initially, a piecewise linear approximation of the binary edge map is obtained. From any two of the resulting linear segments, a Linear Segment Pair (LSP) is formed and several of its attributes are computed. These attributes allow the method to reject or select the LSPs through symbolic rules and coarse numeric thresholds. Grouping the LSPs into couples is governed by additional attributes and rules, with the nal representation consisting of ordered sets of LSPs. The application to shape description, object recognition, and stereo correspondence is presented. This segmentation method is useful for a broad range of images; it has been used in a robot vision system which is capable of manipulating three-dimensional, overlapping, real-world objects in close to real time.