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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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Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper presented a robust pothole detection algorithm that is both accurate and computationally efficient, where a dense disparity map is first transformed to better distinguish between damaged and undamaged road areas.
Abstract: Pothole detection is one of the most important tasks for road maintenance. Computer vision approaches are generally based on either 2D road image analysis or 3D road surface modeling. However, these two categories are always used independently. Furthermore, the pothole detection accuracy is still far from satisfactory. Therefore, in this paper, we present a robust pothole detection algorithm that is both accurate and computationally efficient. A dense disparity map is first transformed to better distinguish between damaged and undamaged road areas. To achieve greater disparity transformation efficiency, golden section search and dynamic programming are utilized to estimate the transformation parameters. Otsu’s thresholding method is then used to extract potential undamaged road areas from the transformed disparity map. The disparities in the extracted areas are modeled by a quadratic surface using least squares fitting. To improve disparity map modeling robustness, the surface normal is also integrated into the surface modeling process. Furthermore, random sample consensus is utilized to reduce the effects caused by outliers. By comparing the difference between the actual and modeled disparity maps, the potholes can be detected accurately. Finally, the point clouds of the detected potholes are extracted from the reconstructed 3D road surface. The experimental results show that the successful detection accuracy of the proposed system is around 98.7% and the overall pixel-level accuracy is approximately 99.6%.

53 citations

Journal ArticleDOI
TL;DR: A novel method for embedding and detecting a chaotic watermark in the digital spatial domain of color facial images, based on localizing salient facial features, is introduced.
Abstract: We introduce a novel method for embedding and detecting a chaotic watermark in the digital spatial domain of color facial images, based on localizing salient facial features. These features define a certain area on which the watermark is embedded and detected. An assessment of the watermarking robustness is done experimentally, by testing resistance to several attacks, such as compression, filtering, noise addition, scaling, cropping and rotation.

52 citations

Proceedings ArticleDOI
31 May 1998
TL;DR: A method for the restoration of cracks on a painting is developed, which detects the local minima by using a morphological high-pass operator, called top-hat transformation and proposes two crack filling methods, one which is based on order statistics and another one using anisotropic diffusion.
Abstract: In this paper we develop a method for the restoration of cracks on a painting. First, we detect the local minima (they can be either cracks or painting brush strokes), by using a morphological high-pass operator, called top-hat transformation. The crack filling procedure must be applied only on the cracks and not on these dark brush strokes, which are also detected. In order to separate these brush strokes from cracks, we use the Hue and Saturation information in the HSV or HSI color space. The separation is obtained by classification through the implementation of the MRBF neural network. Alternatively, a semi-automatic method is described for this separation. The primitive geometric shape-matching property of the morphological opening can be used to separate brush strokes, which have a specific shape. Finally, we propose two crack filling methods, one which is based on order statistics and another one using anisotropic diffusion. The results on painting crack restoration were very good.

52 citations

Proceedings ArticleDOI
02 Jul 1997
TL;DR: This paper presents a watermarking algorithm for copyright protection of digital images that controls embedding, detection and reconstruction of the copyright label in grayscale or color digital image.
Abstract: This paper presents a watermarking algorithm for copyright protection of digital images. A copyright label represented by a binary image is embedded in grayscale or color digital image. A mixing dynamical system controls embedding, detection and reconstruction of the copyright label. Detection of the watermark is succeeded either by direct reconstruction of the watermark as a binary image or by using statistical hypothesis testing.

52 citations

Journal ArticleDOI
TL;DR: A comprehensive review of a number of (semi‐) automated FISH and IHC image processing systems, focusing on the algorithmic aspects of each technique, verifies the increasingly important role of such methods in FISHand IHC.
Abstract: Fluorescent in-situ hybridization (FISH) and immunohistochemistry (IHC) constitute a pair of complimentary techniques for detecting gene amplification and overexpression, respectively. The advantages of IHC include relatively cheap materials and high sample durability, while FISH is the more accurate and reproducible method. Evaluation of FISH and IHC images is still largely performed manually, with automated or semiautomated techniques increasing in popularity. Here, we provide a comprehensive review of a number of (semi-) automated FISH and IHC image processing systems, focusing on the algorithmic aspects of each technique. Our review verifies the increasingly important role of such methods in FISH and IHC; however, manual intervention is still necessary in order to resolve particularly challenging or ambiguous cases. In addition, large-scale validation is required in order for these systems to enter standard clinical practice.

52 citations


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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