Cees Snoek

The paper Evaluation of Color Descriptors for Object and Scene Recognition by Koen van de Sande, Theo Gevers, and Cees Snoek is available online now. Image category recognition is important to access visual information on the level of objects and scene types. So far, intensity-based descriptors have been widely used. To increase illumination invariance and discriminative power, color descriptors have been proposed only recently. As many descriptors exist, a structured overview of color invariant descriptors in the context of image category recognition is required. Therefore, this paper studies the invariance properties and the distinctiveness of color descriptors in a structured way. The invariance properties of color descriptors are shown analytically using a taxonomy based on invariance properties with respect to photometric transformations. The distinctiveness of color descriptors is assessed experimentally using two benchmarks from the image domain and the video domain. From the theoretical and experimental results, it can be derived that invariance to light intensity changes and light color changes affects category recognition. The results reveal further that, for light intensity changes, the usefulness of invariance is category-specific.

During the past two weeks I spent some pleasant time in Germany for a Dagstuhl meeting, the ACM Multimedia PC meeting, and the ICME conference. My personal highlight of all events was the Dagstuhl meeting on Contextual and Social Media Understanding and Usage. This was a very interesting experience. The Dagstuhl concept works as follows: you lock a bunch of people that work on a similar research topic in a castle-like venue in the middle of nowhere. You make sure that they are fed at regular intervals during the day, you group them based on specific interests, and what will happen is that they start to think and talk about novel research ideas. I ended up in a group with Alex Hauptmann, Gareth Jones, and Stéphane Marchand-Maillet. We discussed the possibility of opening a huge central repository for multimedia data, features, software, and experimental results to boost research in contextual and social media understanding. I hope this idea will generate some activity the coming months. Apart from discussing the social aspects of multimedia research, the Dagstuhl meeting was also a very engaging social activity, I especially liked the discussions in the wine cellar :) I owe a big thanks to the organizers of the workshop: Susanne Boll, Mohan Kankanhalli, Gopal Pingali, and Svetha Venkatesh, for inviting me, and of course to the fellow participants (see group photo) for the great atmosphere. I hope to come back to this place at some later point in time.