Ioannis Pitas

Bio: Ioannis Pitas is an academic researcher from Aristotle University of Thessaloniki. The author has contributed to research in topics: Facial recognition system & Digital watermarking. The author has an hindex of 76, co-authored 795 publications receiving 24787 citations. Previous affiliations of Ioannis Pitas include University of Bristol & University of York.

Embedded UAV Real-Time Visual Object Detection and Tracking

Abstract: The use of camera-equipped Unmanned Aerial Vehicles (UAVs, or “drones”) for a wide range of aerial video capturing applications, including media production, surveillance, search and rescue operations, etc., has exploded in recent years. Technological progress has led to commercially available UAVs with a degree of cognitive autonomy and perceptual capabilities, such as automated, on-line detection and tracking of target objects upon the captured footage. However, the limited computational hardware, the possibly high camera-to-target distance and the fact that both the UAV/camera and the target(s) are moving, makes it challenging to achieve both high accuracy and stable real-time performance. In this paper, the current state-of-the-art on real-time object detection/tracking is overviewed. Additionally, a relevant, modular implementation suitable for on-drone execution (running on top of the popular Robot Operating System) is presented and empirically evaluated on a number of relevant datasets. The results indicate that a sophisticated, neural network-based detection and tracking system can be deployed at real-time even on embedded devices.

Autonomous Unmanned Aerial Vehicles Filming In Dynamic Unstructured Outdoor Environments [Applications Corner]

Abstract: The recent mass commercialization of affordable unmanned aerial vehicles (UAVs), known as drones, has significantly altered the media production landscape, allowing for the easy acquisition of impressive aerial footage. Relevant applications include the production of movies, TV shows, or commercials as well as the filming of outdoor events or news stories. In the near future, increased drone autonomy is expected to reduce shooting costs and shift focus to the creative process, rather than the minutiae of UAV operation. This article introduces and surveys the emerging field of autonomous UAV filming and familiarizes the reader with the inherent signal processing aspects and challenges.

Positive and Negative Label Propagations

Abstract: This paper extends the state-of-the-art label propagation (LP) framework in the propagation of negative labels. More specifically, the state-of-the-art LP methods propagate information of the form “the sample $i$ should be assigned the label $k$ .” The proposed method extends the state-of-the-art framework by considering additional information of the form “the sample $i$ should not be assigned the label $k$ .” A theoretical analysis is presented in order to include negative LP in the problem formulation. Moreover, a method for selecting the negative labels in cases when they are not inherent from the data structure is presented. Furthermore, the incorporation of negative label information in two multigraph LP methods is presented. Finally, a discussion on the proposed algorithm extension to out of sample data, as well as scalability issues, is presented. Experimental results in various scenarios showed that the incorporation of negative label information increases, in all cases, the classification accuracy of the state of the art.

Multi-view Human Action Recognition: A Survey

Abstract: While single-view human action recognition has attracted considerable research study in the last three decades, multi-view action recognition is, still, a less exploited field. This paper provides a comprehensive survey of multi-view human action recognition approaches. The approaches are reviewed following an application-based categorization: methods are categorized based on their ability to operate using a fixed or an arbitrary number of cameras. Finally, benchmark databases frequently used for evaluation of multi-view approaches are briefly described.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Face recognition: A literature survey

Abstract: As one of the most successful applications of image analysis and understanding, face recognition has recently received significant attention, especially during the past several years. At least two reasons account for this trend: the first is the wide range of commercial and law enforcement applications, and the second is the availability of feasible technologies after 30 years of research. Even though current machine recognition systems have reached a certain level of maturity, their success is limited by the conditions imposed by many real applications. For example, recognition of face images acquired in an outdoor environment with changes in illumination and/or pose remains a largely unsolved problem. In other words, current systems are still far away from the capability of the human perception system.This paper provides an up-to-date critical survey of still- and video-based face recognition research. There are two underlying motivations for us to write this survey paper: the first is to provide an up-to-date review of the existing literature, and the second is to offer some insights into the studies of machine recognition of faces. To provide a comprehensive survey, we not only categorize existing recognition techniques but also present detailed descriptions of representative methods within each category. In addition, relevant topics such as psychophysical studies, system evaluation, and issues of illumination and pose variation are covered.

Detecting faces in images: a survey

Abstract: Images containing faces are essential to intelligent vision-based human-computer interaction, and research efforts in face processing include face recognition, face tracking, pose estimation and expression recognition. However, many reported methods assume that the faces in an image or an image sequence have been identified and localized. To build fully automated systems that analyze the information contained in face images, robust and efficient face detection algorithms are required. Given a single image, the goal of face detection is to identify all image regions which contain a face, regardless of its 3D position, orientation and lighting conditions. Such a problem is challenging because faces are non-rigid and have a high degree of variability in size, shape, color and texture. Numerous techniques have been developed to detect faces in a single image, and the purpose of this paper is to categorize and evaluate these algorithms. We also discuss relevant issues such as data collection, evaluation metrics and benchmarking. After analyzing these algorithms and identifying their limitations, we conclude with several promising directions for future research.