MEDIAL-POINT DESCRIPTION OF SHAPE - A REPRESENTATION FOR ACTION CODING AND ITS PSYCHOPHYSICAL CORRELATES

We describe a region-based shape representation that might be particul arly useful from a biological perspective because it promotes the loca lization of objects, and object parts relative to each other. The prop osed medial-point representation is similar to medial-axis type repres entations, but it is more compact. The medial points are those points along the medial axis that are equidistant from the longest segments o f the boundary, therefore they represent the largest amount of edge in formation. The main advantage is that the original image can be reduce d to a small number of points. We also provide psychophysical correlat es of the representation for shapes with increasing complexity. Using a reverse mapping technique, we find that variations of contrast sensi tivity within figures are defined by the shape of the bounding contour , and the peaks in the sensitivity maps correspond to the medial point s of the proposed representation. (C) 1998 Elsevier Science Ltd. All r ights reserved.