Computer Science Colloquium - Prof. Laurent Najman, ESIEE Paris

Titel: Power-Watershed: a graph-based optimization framework for image and data processing

Abstract:

The watershed is a tool originally developed in the mathematical morphology community for image segmentation. Over time, numerous adaptations have emerged, proving its applicability beyond image processing. Particularly, it has demonstrated its value in tasks such as data classification and filtering. This presentation aims to highlight the continued relevance of the watershed method in the era of deep learning. Following an overview of cutting-edge achievements attainable through the watershed technique, our focus shifts to the Power Watershed (PW) optimization framework, within the context of image and data processing. Existing literature recognizes the PW framework’s potential, especially when applied to prominent graph-based data processing algorithms like random walker, isoperimetric partitioning, ratio-cut clustering, multi-cut, and shortest path filters. The result is faster, yet consistent, solutions.During the talk, we delve into the PW framework’s underlying concept: the utilization of contrast invariance within data. This concept is elucidated using hypothetical images and experimental demonstrations. Importantly, the principles from this framework can be adapted for a wide range of graph-based cost minimization methods, and seamlessly integrated with deep learning networks, leading to scalable algorithms that consistently deliver high-quality outcomes.

Short Bio:

Laurent Najman received the Habilitation à Diriger les Recherches in 2006 from the University of Marne-la-Vallée, a Ph.D. in applied mathematics from Paris-Dauphine University in 1994 with the highest honor (Félicitations du Jury) and an “Ingénieur” degree from the Ecole des Mines de Paris in 1991. After earning his engineering degree, he worked in the Central Research Laboratories of Thomson-CSF for three years, working on some problems of infrared image segmentation using mathematical morphology. He then joined a start-up company named Animation Science in 1995, as director of research and development. The technology of particle systems for computer graphics and scientific visualization, developed by the company under his technical leadership, received several awards. These include the European Information Technology Prize 1997 awarded by the European Commission (Esprit program) and by the European Council for Applied Science and Engineering and the Hottest Products of the Year 1996 awarded by the Computer Graphics World journal. In 1998, he joined OCÉ Print Logic Technologies, as senior scientist. He worked there on various problems of image analysis dedicated to scanning and printing. In 2002, he joined the Computer Sciences Department of ESIEE, Paris, where he is full professor and the leader of the A3SI team of the Laboratoire d’Informatique Gaspard Monge, Université Gustave Eiffel. Since 2025, he has served as the president of AFRIF, the French branch of the International Association for Pattern Recognition. His current research interests include the study of the topology of discrete structures (such as graphs, hierarchies, and simplicial complexes), using discrete mathematical morphology and discrete optimization.