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Author

Ioannis Pitas

Other affiliations: University of Bristol, University of York, University of Toronto  ...read more
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.


Papers
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Proceedings ArticleDOI
27 Apr 1993
TL;DR: A novel approximation of Euclidean distance in Z/sup 2/ is proposed, and a novel algorithm for the computation of Voronoi tessellation and Delauney triangulation is presented based on this approximation.
Abstract: A novel approximation of Euclidean distance in Z/sup 2/ is proposed, and a novel algorithm for the computation of Voronoi tessellation and Delauney triangulation is presented based on this approximation. The proposed method has low computational complexity (of order O(1/N)) and allows parallel implementation. Mathematical morphology is used to implement the Voronoi tessellation and the Delauney triangulation. >

8 citations

Proceedings ArticleDOI
25 Sep 2016
TL;DR: This work proposes a multi-view temporal video segmentation approach that employs a Gaussian scoring process for determining the best segmentation positions, and compares the temporal segmentation results of the proposed method to both single-view andMulti-view methods.
Abstract: In this work, we propose a multi-view temporal video segmentation approach that employs a Gaussian scoring process for determining the best segmentation positions. By exploiting the semantic action information that the dense trajectories video description offers, this method can detect intra-shot actions as well, unlike shot boundary detection approaches. We compare the temporal segmentation results of the proposed method to both single-view and multi-view methods, and also compare the action recognition results obtained on ground truth video segments to the ones obtained on the proposed multi-view segments, on the IMPART multi-view action data set.

8 citations

Proceedings Article
01 Sep 2006
TL;DR: The method has been tested on a variety of sequences with very good results, including a database of video sequences representing human faces changing from the neutral state to the one that represents a fully formed human facial expression.
Abstract: This paper presents a method for generalizing human facial expressions or personalizing (cloning) them from one person to completely different persons, by means of a statistical analysis of human facial expressions coming from various persons. The data used for the statistical analysis are obtained by tracking a generic facial wireframe model in video sequences depicting the formation of the different human facial expressions, starting from a neutral state. Wireframe node tracking is performed by a pyramidal variant of the well-known Kanade-Lucas-Tomasi (KLT) tracker. The loss of tracked features is handled through a model deformation procedure increasing the robustness of the tracking algorithm. The dynamic facial expression output model is MPEG-4 compliant. The method has been tested on a variety of sequences with very good results, including a database of video sequences representing human faces changing from the neutral state to the one that represents a fully formed human facial expression.

8 citations

Proceedings Article
01 Jan 2014
TL;DR: Experimental results denote that the proposed approach enhances action classification performance, when compared to the standard approach, and achieves state-of-the-art performance on the Hollywood 3D database designed for the recognition of complex actions in unconstrained environments.
Abstract: In this paper, we propose a method for human action recognition in unconstrained environments based on stereoscopic videos. We describe a video representation scheme that exploits the enriched visual and disparity information that is available for such data. Each stereoscopic video is represented by multiple vectors, evaluated on video locations corresponding to different disparity zones. By using these vectors, multiple action descriptions can be determined that either correspond to specific disparity zones, or combine information appearing in different disparity zones in the classification phase. Experimental results denote that the proposed approach enhances action classification performance, when compared to the standard approach, and achieves state-of-theart performance on the Hollywood 3D database designed for the recognition of complex actions in unconstrained environments.

8 citations

Journal Article
TL;DR: In this article, a scene change detection method is presented, which analyzes both auditory and visual information sources and accounts for their inter-relations and coincidence to semantically identify video scenes.
Abstract: A scene change detection method is presented in this paper, which analyzes both auditory and visual information sources and accounts for their inter-relations and coincidence to semantically identify video scenes. Audio analysis focuses on the segmentation of the audio source into three types of semantic primitives, i.e. silence, speech and music. Further processing on speech segments aims at locating speaker change instants. Video analysis attempts to segment the video source into shots, without the segmentation being affected by camera pans, zoom-ins/outs or significantly high object motion. Results from single source segmentation are in some cases suboptimal. Audio-visual interaction achieves to either enhance single source findings or extract high level semantic information. The aim of this paper is to identify semantically meaningful video scenes by exploiting the temporal correlations of both sources based on the observation that semantic changes are characterized by significant changes in both information sources. Experimentation has been carried on a real TV serial sequence composed of many different scenes with plenty of commercials appearing in-between. The results are proven to be rather promising.

8 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
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 …

33,785 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide an up-to-date critical survey of still-and video-based face recognition research, and provide some insights into the studies of machine recognition of faces.
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.

6,384 citations

Journal ArticleDOI
TL;DR: In this article, the authors categorize and evaluate face detection algorithms and discuss relevant issues such as data collection, evaluation metrics and benchmarking, and conclude with several promising directions for future research.
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.

3,894 citations