2 a Generative Process

We have developed a new Bayesian framework for visual object recognition which is based on the insight that images of objects can be modeled as a conjunction of local features. This framework can be used to both derive an object recognition algorithm and an algorithm for learning the features themselves. The overall approach, called complex feature recognition or CFR, is unique for several reasons: it is broadly applicable to a wide range of object types, it makes constructing object models easy, it is capable of identifying either the class or the identity of an object, and it is computationally eecient { requiring time proportional to the size of the image. Instead of a single simple feature such as an edge, CFR uses a large set of complex features that are learned from experience with model objects. The response of a single complex feature contains much more class information than does a single edge. This signiicantly reduces the number of possible correspondences between the model and the image. In addition, CFR takes advantage of a type of image processing called oriented energy. Oriented energy is used to eeciently pre-process the image to eliminate some of the diiculties associated with changes in lighting and pose.