Coarse-to-Fine Visual Selection

We study visual selection: Detect and roughly localize all instances of a generic object class, such as a face, in a greyscale scene, measuring performance in terms of computation and false alarms. Our approach is sequential testing which is coarse-tone in both in the exploration of poses and the representation of objects. All the tests are all binary and indicate the presence or absence of loose spatial arrangements of oriented edge fragments. Starting from training examples, we recursively nd larger and larger arrangements which are "decomposable," which implies the probability of an arrangement appearing on an object decays slowly with its size. Detection means nding a suucient number of arrangements of each size along a decreasing sequence of pose cells. At the beginning, the tests are simple and universal, accommodating many poses simultaneously, but the false alarm rate is relatively high. Eventually, the tests are more discriminating, but also more complex and dedicated to speciic poses. As a result, the spatial distribution of processing is highly skewed and detection is rapid, but at the expense of (isolated) false alarms which, presumably, could be eliminated with localized, more intensive, processing.