The Weizmann Institute of Science Faculty of Mathematics and Computer Science Vision and Robotics Seminar Room 141 (faculty lounge), Ziskind Building on Sunday, January 15, 2012 at 11:00 Note the unusual day, time and location David Jacobs University of Maryland will speak on Fast, Wavelet-Based Image Comparison Abstract: We wish to compare images in a way that allows us to consider two images to be similar even when there are some deformations that change their shape, or lighting variation that changes their intensity. I will discuss our recent work showing that we can perform image comparisons that are insensitive to these transformations very efficiently by operating in the wavelet domain. First, I will present an approximation algorithm for computing the Earth Mover-Fs Distance (EMD), a metric for comparing probability distributions. This can be used to match image descriptors, or histograms, accounting for deformations or other variations in appearance. Using a wavelet-based representation, we construct an accurate, linear time algorithm for computing the EMD. Next, we consider image matching in the presence of lighting variation. We attack this problem by defining a local cost on small image changes that is insensitive to the effects of lighting variation. We use this cost to define a Riemannian manifold of images, in which geodesic distance is used to measure the similarity of images when there are larger variations in lighting. We show that these geodesic distances can also be approximated efficiently by computing them in the wavelet domain. Combining these ideas, we obtain a single image comparison method that is insensitive to lighting changes and moderate changes in shape, and that can be computed about as quickly as normalized correlation. We demonstrate that this produces state-of-the-art face recognition results in the presence of lighting and expression changes. --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Yaeli Malka <yaeli.malka@weizmann.ac.il>