Cette thèse traite de la détection et de la ré-identification de personnes dans un environnement instrumenté par un réseau de caméras à champ disjoint. Elle est à la confluence des communautés Recherche Opérationnelle et Vision car elle s'appuie sur des techniques d'optimisation combinatoire pour formaliser de nouvelles modalités de vision par ordinateur. Dans ce contexte, un détecteur visuel de personnes, basé sur la programmation linéaire en nombres entiers, est tout d'abord proposé. Son originalité est de prendre en compte le coût de traitement et non uniquement les performances de détection. Ce détecteur est évalué et comparé aux détecteurs de la littérature les plus performants. Ces expérimentations menées sur deux bases de données publiques mettent clairement en évidence l'intérêt de notre détecteur en terme de coût de traitement avec garantie de performance de détection. La seconde partie de la thèse porte sur la modalité de ré-identification de personnes. L'originalité de notre approche, dénommée D-NCR (pour Directed Network Consistent Re-identification), est de prendre explicitement en compte les temps minimum de transit des personnes dans le réseau de caméras et sa topologie pour améliorer la performance de la ré-identification. On montre que ce problème s'apparente à une recherche de chemins disjoints particuliers à profit maximum dans un graphe orienté. Un programme linéaire en nombres entiers est proposé pour sa modélisation et résolution. Les évaluations réalisées sur une base publique d'images sont prometteuses et montrent le potentiel de cette approche. / This thesis deals with people detection and re-identification in an environment instrumented by a network of disjoint-field cameras. It stands at the confluence of the Operational Research and Computer Vision communities as combinatorial optimization techniques are used to formalize new computer vision methods. In this context, a people visual detector, based on mixed-integer programming, is first propose that simultaneously take computation time and detection performances into account. This detector is evaluated and compared to the best detectors of the literature. These experiments, conducted on two public databases, clearly demonstrate the interest of our detector in terms of processing time with detection performance guarantee. The second part of the thesis deals with people re-identification. Our novel approach, called D-NCR (Directed Network Consistent Re-identification), explicitly takes minimum transit times in the camera network into account, as well as the network topology, in order to improve the re-identification performance. This problem is similar to the determination of particular maximum-profitable independent paths in an oriented graph. A mixed-integer program is proposed to model and solve this problem. The experiments made on a public dataset sound promising and tend to prove the potential of the approach.

There has been a significant number of security concerns in recent times; as a result, security cameras have been installed to monitor activities and to prevent crimes in most public places. These analysis are done either through video analytic or forensic analysis operations on human observations. To this end, within the research context of this thesis, a proactive machine vision based military recognition system has been developed to help monitor activities in the military environment. The proposed object detection, recognition and re-identification systems have been presented in this thesis. A novel technique for military personnel recognition is presented in this thesis. Initially the detected camouflaged personnel are segmented using a grabcut segmentation algorithm. Since in general a camouflaged personnel's uniform appears to be similar both at the top and the bottom of the body, an image patch is initially extracted from the segmented foreground image and used as the region of interest. Subsequently the colour and texture features are extracted from each patch and used for classification. A second approach for personnel recognition is proposed through the recognition of the badge on the cap of a military person. A feature matching metric based on the extracted Speed Up Robust Features (SURF) from the badge on a personnel's cap enabled the recognition of the personnel's arm of service. A state-of-the-art technique for recognising vehicle types irrespective of their view angle is also presented in this thesis. Vehicles are initially detected and segmented using a Gaussian Mixture Model (GMM) based foreground/background segmentation algorithm. A Canny Edge Detection (CED) stage, followed by morphological operations are used as pre-processing stage to help enhance foreground vehicular object detection and segmentation. Subsequently, Region, Histogram Oriented Gradient (HOG) and Local Binary Pattern (LBP) features are extracted from the refined foreground vehicle object and used as features for vehicle type recognition. Two different datasets with variant views of front/rear and angle are used and combined for testing the proposed technique. For night-time video analytics and forensics, the thesis presents a novel approach to pedestrian detection and vehicle type recognition. A novel feature acquisition technique named, CENTROG, is proposed for pedestrian detection and vehicle type recognition in this thesis. Thermal images containing pedestrians and vehicular objects are used to analyse the performance of the proposed algorithms. The video is initially segmented using a GMM based foreground object segmentation algorithm. A CED based pre-processing step is used to enhance segmentation accuracy prior using Census Transforms for initial feature extraction. HOG features are then extracted from the Census transformed images and used for detection and recognition respectively of human and vehicular objects in thermal images. Finally, a novel technique for people re-identification is proposed in this thesis based on using low-level colour features and mid-level attributes. The low-level colour histogram bin values were normalised to 0 and 1. A publicly available dataset (VIPeR) and a self constructed dataset have been used in the experiments conducted with 7 clothing attributes and low-level colour histogram features. These 7 attributes are detected using features extracted from 5 different regions of a detected human object using an SVM classifier. The low-level colour features were extracted from the regions of a detected human object. These 5 regions are obtained by human object segmentation and subsequent body part sub-division. People are re-identified by computing the Euclidean distance between a probe and the gallery image sets. The experiments conducted using SVM classifier and Euclidean distance has proven that the proposed techniques attained all of the aforementioned goals. The colour and texture features proposed for camouflage military personnel recognition surpasses the state-of-the-art methods. Similarly, experiments prove that combining features performed best when recognising vehicles in different views subsequent to initial training based on multi-views. In the same vein, the proposed CENTROG technique performed better than the state-of-the-art CENTRIST technique for both pedestrian detection and vehicle type recognition at night-time using thermal images. Finally, we show that the proposed 7 mid-level attributes and the low-level features results in improved performance accuracy for people re-identification.

Cette thèse CIFRE est effectuée dans un contexte industriel et présente un framework complet pour la détection, le suivi mono-caméra et de la ré-identification de personnes dans le contexte multi-caméras. Les performances élevés et le traitement en temps réel sont les deux contraintes critiques ayant guidé ce travail. La détection de personnes vise à localiser/délimiter les gens dans les séquences vidéo. Le détecteur proposé est basé sur une cascade de classifieurs de type LogitBoost appliqué sur des descripteurs de covariances. Une approche existante a fortement été optimisée, la rendant applicable en temps réel et fournissant de meilleures performances. La méthode d'optimisation est généralisable à d'autres types de détecteurs d'objets. Le suivi mono-caméra vise à fournir un ensemble d'images de chaque personne observée par chaque caméra afin d'extraire sa signature visuelle, ainsi qu'à fournir certaines informations du monde réel pour l'amélioration de la ré-identification. Ceci est réalisé par le suivi de points SIFT à l'aide d'une filtre à particules, ainsi qu'une méthode d'association de données qui infère le suivi des objets et qui gère la majorité des cas de figures possible, notamment les occultations. Enfin, la ré-identification de personnes est réalisée avec une approche basée sur l'apparence globale en améliorant grandement une approche existante, obtenant de meilleures performances tout en étabt applicable en temps réel. Une partie "conscience du contexte" est introduite afin de gérer le changement d'orientation des personnes, améliorant les performances dans le cas d'applications réelles. / This thesis is performed in industrial context and presents a whole framework for people detection and tracking in a camera network. It addresses the main process steps: people detection, people tracking in mono-camera context, and people re-identification in multi-camera context. High performances and real-time processing are considered as strong constraints. People detection aims to localise and delimits people in video sequences. The proposed people detection is performed using a cascade of classifiers trained using LogitBoost algorithm on region covariance descriptors. A state of the art approach is strongly optimized to process in real time and to provide better detection performances. The optimization scheme is generalizable to many other kind of detectors where all possible weak classifiers cannot be reasonably tested. People tracking in mono-camera context aims to provide a set of reliable images of every observed person by each camera, to extract his visual signature, and it provides some useful real world information for re-identification purpose. It is achieved by tracking SIFT features using a specific particle filter in addition to a data association framework which infer object tracking from SIFT points one, and which deals with most of possible cases, especially occlusions. Finally, people re-identification is performed using an appearance based approach by improving a state of the art approach, providing better performances while keeping the real-time processing advantage. A context-aware part is introduced to robustify the visual signature against people orientations, ensuring better re-identification performances in real application case.