Description of Shape using Orientation and Propagation Flow

Candidate: Menczel,Yaron


A new theory for the partition of an image into its syntactical primitives is introduced. The method uses edge segments and their orientation to mark an image with useful syntactical information. The marking is done by defining a flow initiating from the boundary and propagating inward into the shape. Three algorithms are introduced. The first sends flow waves in a direction perpendicular to the edges into the object. The second algorithm is an iterative version of the first algorithm, with the addition that an edge detector is constantly applied on the growing object. The third labels the edges with their orientation and then iteratively applies a majority vote selection to spread the orientation with unlabeled pixels inactive in the voting process. The propagation is moderated by a number of heuristics that ensure local and global support within the flow. The flow carries orientation data and spreads the information to all interior pixels. A connected component algorithm based on orientation is then used to construct segments of uniform orientation. These segments constitute the basis of a structural description. The new approach is compared to other methods of segmentation and representation of shapes. These other methods are not always capable of explaining human perception of shapes in a uniform and unique way. Methods that are designed to deal with simple perceptual domains are not capable of dealing with occlusion, texture, touching bodies, and subjective contours. In contrast, this new proposal is shown to work with simple figures as well as more real world complex images. Several examples are given to show the usefulness of the approach. In particular, we give an implementation of a system that performs automatic character recognition based on this method.