Browsing by Author "Marques, Jorge S."
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- Automatic tracking of multiple pedestrians with group formation and occlusionsPublication . Jorge, Pedro; Abrantes, Arnaldo; Marques, Jorge S.This work addresses the problem of automatic track ing of pedestrians observed by a fixed camera in out door scenes. Tracking isolated pedestrians is not a difficult task. The challenge arises when the track ing system has to deal with temporary occlusions and groups of pedestrians. In both cases it is not possi ble to track each pedestrian during the whole video sequence. However, the system should be able to rec ognize each pedestrian as soon as he/she becomes vis ible and isolated from the group. This paper presents methods to tackle these difficulties. The proposed sys tem is based on a hierarchical approach which allows the application of the same methods for tracking iso lated pedestrians and groups.
- Estimation of 3D shapes using active surface modelsPublication . Nascimento, Jose; Marques, Jorge S.This paper addresses the estimation of surfaces from a set of 3D points using the unified framework described in [1]. This framework proposes the use of competitive learning for curve estimation, i.e., a set of points is defined on a deformable curve and they all compete to represent the available data. This paper extends the use of the unified framework to surface estimation. It o shown that competitive learning performes better than snakes, improving the model performance in the presence of concavities and allowing to desciminate close surfaces. The proposed model is evaluated in this paper using syntheticdata and medical images (MRI and ultrasound images).
- Sistema para pesquisa de imagens com retroacção de relevânciaPublication . Jesus, Rui; Abrantes, Arnaldo; Marques, Jorge S.Recentemente, a retroacção de relevância tem sido utilizada para melhorar o desempenho dos sistemas de pesquisa em base de dados de imagens. Este artigo apresenta um método de Retroacção de Relevância baseado no classificador de Mínimos Quadrados Regularizado e numa técnica de selecção de imagens que permite aumentar a capacidade de aprendizagem do método. São apresentados resultados de testes experimentais.
- Tracking with Bayesian networks: extension to arbitrary topologiesPublication . Jorge, Pedro; Abrantes, Arnaldo; Marques, Jorge S.It was recently proposed an object tracking method, which is able to deal with object occlusions and group tracking, using Bayesian networks. The Bayesian network (BN) tracker has shown promising results in difficult situations but its architecture is limited to a maximum of 2 parents/2 children per node, in order to avoid the combinatorial explosion and difficult network generation procedures from the video signal. This paper addresses the major limitation of the BN tracker and presents a method to generalize the tracker to cope with arbitrary topologies, allowing the tracker to operate in more complex scenes.