Robust multiple-people tracking using color-based particle filters

Presentado al 3rd Iberian Conference on Pattern Recognition and Image Analysis (IbPRIA-2007) celebrado en Girona (Spain) del 6 al 8 de junio.Robust and accurate people tracking is a key task in many promising computer-vision applications. One must deal with non-rigid targets in open-world scenarios, whose shape and appearance evolve over time. Targets may interact, causing partial or complete occlusions. This paper improves tracking by means of particle filtering, where occlusions are handled considering the target's predicted trajectories. Model drift is tackled by careful updating, based on the history of likelihood measures. A colour-based likelihood, computed from histogram similarity, is used. Experiments are carried out using sequences from the CAVIAR database.This work has been supported by the Catalan Research Agency (AGAUR), by the Spanish Ministry of Education (MEC) under projects TIC2003-08865 and DPI-2004-5414, and by the EC grant IST-027110 under the HERMES project.Peer Reviewe

Multimodal feedback fusion of laser, image and temporal information

Trabajo presentado a la 8th International Conference on Distributed Smart Cameras (ICDSC) celebrada en Venecia (Italia) del 4 al 7 de noviembre de 2014.In the present paper, we propose a highly accurate and robust people detector, which works well under highly variant and uncertain conditions, such as occlusions, false positives and false detections. These adverse conditions, which initially motivated this research, occur when a robotic platform navigates in an urban environment, and although the scope is originally within the robotics field, the authors believe that our contributions can be extended to other fields. To this end, we propose a multimodal information fusion consisting of laser and monocular camera information. Laser information is modelled using a set of weak classifiers (Adaboost) to detect people. Camera information is processed by using HOG descriptors to classify person/non person based on a linear SVM. A multi-hypothesis tracker trails the position and velocity of each of the targets, providing temporal information to the fusion, allowing recovery of detections even when the laser segmentation fails. Experimental results show that our feedback-based system outperforms previous state-of-the-art methods in performance and accuracy, and that near real-time detection performance can be achieved.This work has been partially funded by the European project CargoANTs (FP7-SST-2013- 605598) and by the Spanish CICYT project DPI2013-42458-P.Peer Reviewe

Robust multiple-people tracking using color-based particle filters

Robust and accurate people tracking is a key task in many promising computer-vision applications. One must deal with non-rigid targets in open-world scenarios, whose shape and appearance evolve over time. Targets may interact, causing partial or complete occlusions. This paper improves tracking by means of particle filtering, where occlusions are handled considering the target's predicted trajectories. Model drift is tackled by careful updating, based on the history of likelihood measures. A colour-based likelihood, computed from histogram similarity, is used. Experiments are carried out using sequences from the CAVIAR database.Peer Reviewe

Moving cast shadows detection methods for video surveillance applications

Moving cast shadows are a major concern in today’s performance from broad range of many vision-based surveillance applications because they highly difficult the object classification task. Several shadow detection methods have been reported in the literature during the last years. They are mainly divided into two domains. One usually works with static images, whereas the second one uses image sequences, namely video content. In spite of the fact that both cases can be analogously analyzed, there is a difference in the application field. The first case, shadow detection methods can be exploited in order to obtain additional geometric and semantic cues about shape and position of its casting object (’shape from shadows’) as well as the localization of the light source. While in the second one, the main purpose is usually change detection, scene matching or surveillance (usually in a background subtraction context). Shadows can in fact modify in a negative way the shape and color of the target object and therefore affect the performance of scene analysis and interpretation in many applications. This chapter wills mainly reviews shadow detection methods as well as their taxonomies related with the second case, thus aiming at those shadows which are associated with moving objects (moving shadows).Peer Reviewe

Robot interactive learning through human assistance

Peer ReviewedPostprint (author’s final draft

La formación del profesorado en instituciones educativas multiculturales y en situación de vulnerabilidad; base para construir ciudadanía inclusiva e intercultural

Education for an inclusive and intercultural citizenship has recreate in all educational institutions, since the nature of the sociocultural reality in their daily requests for urgent manner the formation of competent citizens to interact with diverse individuals and groups that make and build local, political and cultural communities. It is within reach mutual exchange of goods and cultural values, based on the active promotion of respect and interdependence, allowing the development of projects that benefit the common good, which together different people involved. It is necessary, point and carry out processes of teacher training in their own institutions which are dimensional development of critical judgment to problems hindering social welfare, allowing sensitize people towards assume e introspecten suspicion and evidence of marginalization and exclusion. In this altruistic line is required to learn or awaken the ability to identify the voices of people and groups involved in the processes of social injustice and sociocultural, economic and educational backwardness, be flexible and put us alongside them in their emancipation justified in the research standing reach their dignity and freedom.La educación para una ciudadanía inclusiva e intercultural ha de recrearse en todas las instituciones educativas, dado que la naturaleza de la realidad sociocultural en su cotidianidad solicita de manera inaplazable la formación de ciudadanos competentes para relacionarse con la diversidad de individuos y colectivos que conforman y construyen las comunidades locales, políticas y culturales. Está a nuestro alcance el intercambio recíproco de bienes y valores culturales, basándonos en el respeto activo y la promoción de la interdependencia que permita el desarrollo de proyectos que benefician el bien común, donde participen juntas personas distintas. Es menester, apuntar y llevar cabo procesos de formación del profesorado en sus propias instituciones que tengan como dimensiones el desarrollo del juicio crítico ante problemas que obstaculizan el bienestar social, que permita sensibilizar a las personas en pro que asuman e introspecten toda sospecha y evidencia de marginación y exclusión. En esta línea altruista, se requiere aprender o despertar la capacidad de identificar las voces de las personas y grupos implicados en los procesos de injusticia social y rezago sociocultural, económico y educativo, ser flexibles y situarnos junto a ellos en su emancipación justificada en la pesquisa permanente de alcanzar su dignidad y libertad

PEDAGOGÍA DEL DIÁLOGO EN CLAVE INTERCULTURAL EN LA ESCUELA. UNA APUESTA POR VISIBILIZAR LA CULTURA AFROCOLOMBIANA A TRAVÉS DE LA ENSEÑANZA DE LA HISTORIA DE ÁFRICA

La escuela a través del tiempo ha sido un escenario de enseñanza y aprendizaje en el cual llegan estudiantes y docentes de diferentes lugares del país; pero también desde diferentes lugares del mundo, esto ha generado que dicho espacio académico se convierta en el epicentro de la multiculturalidad y la interculturalidad. Desafortunadamente, la escuela tradicionalmente ha desarrollado sus prácticas pedagógicas en el marco de la monoculturalidad, enfocada en aspectos eurocéntricos, propios de la cultura local, quienes excluyen e inferiorizan a aquellos estudiantes que pertenecen a una cultura diferente, como es el caso de los afrocolombianos. El presente artículo se estructura en cuatro apartados que son el resultado de la investigación fenomenológica que se desarrolló en el programa de Doctorado en Ciencias de la Educación de la Universidad del Magdalena, bajo la línea de investigación, “Pedagogía e intercultura lidad”. En el primer apartado, se presenta un acercamiento epistemológico al concepto de interculturalidad en la escuela desde la perspectiva de diferentes referentes teóricos. Poste riormente, se aborda la normativa vigente en el marco de la educación intercultural. El tercer apartado, hace énfasis en la historia de África, destacando los reinos antiguos más representa tivos. Lo anterior se desarrolla desde las aproximaciones teóricas de la pedagogía del diálogo en clave intercultural. Finalmente, se presentan algunas conclusiones a partir de los desafíos y retos que tiene la escuela para visibilizar la cultura afrocolombiana desde la perspectiva histó rica en el contexto de la educación intercultural

Ultrasound Application to Improve Meat Quality

High-intensity ultrasound offers an alternative to traditional methods of food preservation and is regarded as a green, versatile, popular, and promising emerging technology. Ultrasound generates acoustic cavitation in a liquid medium, developing physical forces that are considered the main mechanism responsible for the observed changes in exposed materials. In meat, ultrasound has been successfully used to improve processes such as mass transfer and marination, tenderization of meat ,and inactivation of microorganisms. It is also an alternative to traditional meat aging methods for improving the quality properties of meat. Moreover, the combination of ultrasonic energy with a sanitizing agent can improve the effect of microbial reduction in foods. This review describes recent potential applications of ultrasound in meat systems, as well as physical and chemical effects of ultrasound treatments on the conservation and modification of processed meat foods

Foreground object segmentation and shadow detection for video sequences in uncontrolled environments

Descripció del recurs: el 20 de juny de 2011Aquesta tesis esta dividida en dos parts principalment. A la primera, es presenta un estudi dels problemes que es poden trobar en la segmentació per moviment, basant-se en aquest estudi es presenta un algoritme genèric el qual es capaç de solucionar d'una forma acurada la majoria dels problemes que es poden trobar en aquest tipus de segmentació. En la segona part, es tracta el tema de les ombres en profunditat. Primer, es presenta un algoritme bottom-up basat en un detector de ombres cromàtiques el qual es capaç no només de solucionar les ombres que es troben a la penombra, sinó també les ombres que podem trobar a l'umbra. Segon, es presenta un sistema topdown basat en un sistema de tracking per tal de trackejar les ombres i d'aquesta manera millorar la detecció de les ombres cromàtiques. En la nostra primera contribució, presentem un anàlisis del possibles problemes que trobem en la segmentació per moviment quan utilitzem el color, els gradients, o la intensitat. La nostra segona aportació es una arquitectura hibrida la qual pot solucionar els principals problemes observats en l'anàlisi, mitjançant la fusió de (i) la informació obtinguda per aquestes tres cues, i (ii) un algoritme de diferencia temporal. Per un costat, em aconseguit millorat els models de color i de gradients per que puguin solucionar tant el problemes amb els canvis de il·luminació global i local (com les ombres no cromàtiques) i els camuflatges en intensitat. A més a més, la informació local es explotada per tal de solucionar el problema dels camuflatges en croma. Per una altra banda, la intensitat es aplicada quan el color i els gradients no estan disponibles degut a problemes en la obtenció d'aquests (es troben fora del rang dinàmic). Addicionalment, la diferencia temporal es inclosa en la segmentació per moviment en el moment en que cap de les cues estudiades no estan disponibles, com per exemple quan el fons de la imatge no es visible en el període de entrenament. Per últim en aquesta primera part, el nostre algoritme també ha de solucionar el problema de les segmentacions fantasma. Com a resultat, el nostre algoritme obté una segmentació robusta i acurada tant en escenaris d'interior com d'exterior, tal i com s'ha demostrat tant quantitativament com qualitativament en els resultats experimentals, mitjançant la comparació del nostre algoritme amb els més coneguts algoritmes de l'estat de l'art. La segmentació en moviment té que tenir en compte el problema de les ombres per tal de evitar distorsions quan intentem segmentar els objectes en moviment. Però molts dels algoritmes que son capaços de detectar les ombres solament son capaços de detectar les ombres a la penombra. En conseqüència, aquestes tècniques no son capaces de detectar les ombres a l'umbra les quals son normalment detectades com part dels objectes en moviment. En aquesta tesis presentem primer una innovadora tècnica que es basa en els models de gradients i de color per tal de separar aquestes ombres cromàtiques dels objectes en moviment. Primerament, construïm tant un model de color en forma de con, com també un model de gradient els quals son invariant a les cromaticitats per tal d'aconseguir fer una segmentació automàtica a la vegada que totes les possibles ombres son detectades. En un segon pas, les regions que poden ser ombres son agrupades considerant "l'efecte blau" i les particions obtingudes mitjançant els gradients. Finalment, analitzem (i) les similituds temporals entre els les estructures locals dels gradients i (ii) les similituds espacials entre els angles cromàtics i les distorsions de la lluminositat de totes les ombres potencials per tal d'identificar les ombres a la umbra. Segon, en el procés top-down després de la detecció dels objectes i les ombres els dos son seguits usant un filtre de Kalman, per d'aquesta manera millorar la detecció de lesombrescromàtiques. Primerament, l'algoritme fa una associacióentre elsblobs (foreground i ombres) i els filtres de Kalman. Segon, es realitza un anàlisis dels possibles casos entre las associacions obtingudes anteriorment, i a més a més es tracten les oclusions mitjançant un Model Probabilístic d'Aparença. Basant-se en aquesta associació es busca la consistència temporal entre els foregrounds, les ombres, i els seus respectius filtres de Kalman. A partir d'aquesta nova associació son estudiats diferents casos, com a resultat les ombres cromàtiques que s'havien perdut son detectades. Finalment, els resultats son utilitzats com a feedback per millorar la detecciódela ombra i del objecte. Pel contrari que altres algoritmes el nostre mètode no fa cap assumpcióapriori sobre la localitzaciódelacàmera, les geometries o les textures de les superfícies, les formes o els possibles tipus de ombres, objectes o de fons de la imatge. Els resultats experimentals mostren la performance i la precisió del nostre algoritme en la detecció de les ombres cromàtiques en diferents materials i amb diferents condicions de il·luminació.This Thesis is mainly divided in two parts. The first one presents a study of motion segmentation problems. Based on this study, a novel algorithm for mobile-object segmentation from a static background scene is also presented. This approach is demonstrated robust and accurate under most of the common problems in motion segmentation. The second one tackles the problem of shadows in depth. Firstly, a bottom-up approach based on a chromatic shadow detector is presented to deal with umbra shadows. Secondly, a top-down approach based on a tracking system has been developed in order to enhance the chromatic shadow detection. In our first contribution, a case analysis of motion segmentation problems is presented by taking into account the problems associated with different cues, namely colour, edge and intensity. Our second contribution is a hybrid architecture which handles the main problems observed in such a case analysis, by fusing (i) the knowledge from these three cues and (ii) a temporal difference algorithm. On the one hand, we enhance the colour and edge models to solve both global/local illumination changes (shadows and highlights) and camouflage in intensity. In addition, local information is exploited to cope with a very challenging problem such as the camouflage in chroma. On the other hand, the intensity cue is also applied when colour and edge cues are not available, such as when beyond the dynamic range. Additionally, temporal difference is included to segment motion when these three cues are not available, such as that background not visible during the training period. Lastly, the approach is enhanced for allowing ghost detection. As a result, our approach obtains very accurate and ro¬bust motion segmentation in both indoor and outdoor scenarios, as quantitatively and qualitatively demonstrated in the experimental results, by comparing our approach with most best-known state-of-the-art approaches. Motion Segmentation has to deal with shadows to avoid distortions when detecting moving objects. Most segmentation approaches dealing with shadow detection are typically restricted to penumbra shadows. Therefore, such techniques cannot cope well with umbra shadows. Consequently, umbra shadows are usually detected as part of moving objects. Firstly, a bottom-up approach for detection and removal of chromatic moving shadows in surveillance scenarios is proposed. Secondly, a top-down approach based on kalman filters to detect and track shadows has been developed in order to enhance the chromatic shadow detection. In the Bottom-up part, the shadow detection approach applies a novel technique based on gradient and colour models for separating chromatic moving shadows from moving objects. Well-known colour and gradient models are extended and improved into an invariant colour cone model and an invariant gradient model, respectively, to perform automatic segmentation while detecting potential shadows. Hereafter, the regions corresponding to potential shadows are grouped by considering "a bluish effect" and an edge partitioning. Lastly, (i) temporal similarities between local gradient structures and (ii) spatial similarities between chrominance angle and brightness distortions are analysed for all potential shadow regions in order to finally identify umbra shadows. In the top-down process, after detection of objects and shadows both are tracked using Kalman filters, in order to enhance the chromatic shadow detection, when it fails to detect a shadow. Firstly, this implies a data association between the blobs (foreground and shadow) and Kalman filters. Secondly, an event analysis of the different data association cases is performed, and occlusion handling is managed by a Probabilistic Appearance Model (PAM). Based on this association, temporal consistency is looked for the association between foregrounds and shadows and their respective Kalman Filters. From this association several cases are studied, as a result lost chromatic shadows are correctly detected. Finally, the tracking results are used as feedback to improve the shadow and object detection. Unlike other approaches, our method does not make any a-priori assumptions about camera location, surface geometries, surface textures, shapes and types of shadows, objects, and background. Experimental results show the performance and accuracy of our approach in different shadowed materials and illumination conditions