Ioannis Pratikakis | Democritus University of Thrace (original) (raw)
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Papers by Ioannis Pratikakis
Proceedings of the First International Conference on Computer Vision Theory and Applications, 2006
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In this paper, a segmentation-free and training-free word spotting method is proposed that allows... more In this paper, a segmentation-free and training-free word spotting method is proposed that allows mobile device users to search instances of a query word in handwritten document collections. The method is based on a document-oriented keypoint and feature extraction pipeline together with a fast feature matching method that permits the pipeline to be effectively employed in the cloud and to be introduced as a service in modern mobile device units. Evaluation results on two segmentation-free historical handwritten datasets show the efficiency of the proposed method in terms of matching accuracy along with its fast retrieval time.
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Computers & Graphics, Jun 1, 2023
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An important step for the document analysis and recognition pipeline is the document image binari... more An important step for the document analysis and recognition pipeline is the document image binarization procedure. In the case of historical handwritten document images, the inherent degradation of the documents requires a preprocessing step aiming to enhance the image and improve the subsequent binarization step. To address this challenge a new document image enhancement method is proposed based on Bio-Inspired Models and especially on the OFF-center ganglion cells of the Human Vision System. Experimental results demonstrate the improvement of standard binarization methods when the proposed enhancement method is used.
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IEEE transactions on intelligent vehicles, Feb 1, 2023
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Computers & Graphics, Aug 1, 2022
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Nova Science Publishers, Inc. eBooks, Jul 21, 2017
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2018 16th International Conference on Frontiers in Handwriting Recognition (ICFHR), 2018
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IEEE Transactions on Multimedia, 2017
Performance evaluation is one of the main research topics in information retrieval. Evaluation me... more Performance evaluation is one of the main research topics in information retrieval. Evaluation metrics are used to quantify various performance aspects of a retrieval method. These metrics assist in identifying the optimum method for a specific retrieval challenge but also to allow its parameters fine-tuning in order to achieve a robust operation for a given set of requirements specification. In this work, we present RETRIEVAL, a Web-based integrated information retrieval performance evaluation platform. It offers a number of metrics that are popular within the scientific community, so as to compose an efficient framework for implementing performance evaluation. We discuss the functionality of RETRIEVAL by citing important aspects such as the data input approaches, the user-level performance metrics parameterization, the evaluation scenarios, the interactive plots, and the performance reports repository that offers both archiving and download functionalities.
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2016 Digital Media Industry & Academic Forum (DMIAF), 2016
The aim of this research is to achieve spatial consistency of the UV map. We present an approach ... more The aim of this research is to achieve spatial consistency of the UV map. We present an approach to produce a fully spatially consistent UV mapping based on the planar parameterisation of the mesh. We apply our method on a 3D digital replica of an ancient Greek Lekythos vessel. We parameterise the mesh of a 3D model onto a unit square 2D plane using computational conformal geometry techniques. The proposed method is genus independent, due to an iterative 3D mesh cutting procedure. Having now the texture of a 3D model depicted on a spatially continuous two dimensional structure enables us to efficiently apply a vast range of image processing based techniques and algorithms.
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2017 14th IAPR International Conference on Document Analysis and Recognition (ICDAR), 2017
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2020 IEEE International Joint Conference on Biometrics (IJCB), 2020
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Pattern Recognition, 2016
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2016 15th International Conference on Frontiers in Handwriting Recognition (ICFHR), 2016
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The Visual Computer, May 2, 2016
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Pattern Recognition, Apr 1, 2016
The problem of facial expression recognition in dynamic sequences of 3D face scans has received a... more The problem of facial expression recognition in dynamic sequences of 3D face scans has received a significant amount of attention in the recent past whereas the problem of retrieval in this type of data has not. A novel retrieval methodology for such data is introduced in this paper. The proposed methodology automatically detects specific facial landmarks and uses them to create a descriptor. This descriptor is the concatenation of three sub-descriptors which capture topological as well as geometric information of the 3D face scans. The motivation behind the proposed hybrid facial expression descriptor is the fact that some facial expressions, like happiness and surprise, are characterized by obvious changes in the mouth topology while others, like anger, fear and sadness, produce geometric but no significant topological changes. The proposed retrieval scheme exploits the Dynamic Time Warping technique in order to compare descriptors corresponding to different 3D facial sequences. A detailed evaluation of the introduced retrieval scheme is presented showing that it outperforms previous state-of-the-art retrieval schemes. Experiments have been conducted using the six prototypical expressions of the standard dataset BU-4DFE and the eight prototypical expressions of the recently available dataset BP4D-Spontaneous. Finally, a majority voting scheme based on the retrieval results is used to achieve unsupervised dynamic 3D facial expression recognition. The achieved classification accuracy is comparable to the state-of-the-art supervised dynamic 3D facial expression recognition techniques. HighlightsWe illustrate a novel retrieval methodology for dynamic sequences of 3D face scans.We present a detailed evaluation of the introduced retrieval scheme.BU-4DFE and BP4D-Spontaneous data sets were used for experiments.Retrieval results are used to achieve unsupervised facial expression recognition.The presented results outperform state-of-the-art retrieval schemes.
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International Journal of Image and Graphics, Jul 1, 2019
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Despite numerous recent efforts, 3D object retrieval based on partial shape queries remains a cha... more Despite numerous recent efforts, 3D object retrieval based on partial shape queries remains a challenging problem, far from being solved. The problem can be defined as: given a partial view of a shape as query, retrieve all partially similar 3D models from a repository. The objective of this track is to evaluate the performance of partial 3D object retrieval methods, for partial shape queries of various scan qualities and degrees of partiality. The retrieval problem is often found in cultural heritage applications, for which partial scans of objects query a dataset of geometrically distinct classes.
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Proceedings of the First International Conference on Computer Vision Theory and Applications, 2006
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In this paper, a segmentation-free and training-free word spotting method is proposed that allows... more In this paper, a segmentation-free and training-free word spotting method is proposed that allows mobile device users to search instances of a query word in handwritten document collections. The method is based on a document-oriented keypoint and feature extraction pipeline together with a fast feature matching method that permits the pipeline to be effectively employed in the cloud and to be introduced as a service in modern mobile device units. Evaluation results on two segmentation-free historical handwritten datasets show the efficiency of the proposed method in terms of matching accuracy along with its fast retrieval time.
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Computers & Graphics, Jun 1, 2023
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An important step for the document analysis and recognition pipeline is the document image binari... more An important step for the document analysis and recognition pipeline is the document image binarization procedure. In the case of historical handwritten document images, the inherent degradation of the documents requires a preprocessing step aiming to enhance the image and improve the subsequent binarization step. To address this challenge a new document image enhancement method is proposed based on Bio-Inspired Models and especially on the OFF-center ganglion cells of the Human Vision System. Experimental results demonstrate the improvement of standard binarization methods when the proposed enhancement method is used.
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IEEE transactions on intelligent vehicles, Feb 1, 2023
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Computers & Graphics, Aug 1, 2022
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Nova Science Publishers, Inc. eBooks, Jul 21, 2017
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2018 16th International Conference on Frontiers in Handwriting Recognition (ICFHR), 2018
Bookmarks Related papers MentionsView impact
IEEE Transactions on Multimedia, 2017
Performance evaluation is one of the main research topics in information retrieval. Evaluation me... more Performance evaluation is one of the main research topics in information retrieval. Evaluation metrics are used to quantify various performance aspects of a retrieval method. These metrics assist in identifying the optimum method for a specific retrieval challenge but also to allow its parameters fine-tuning in order to achieve a robust operation for a given set of requirements specification. In this work, we present RETRIEVAL, a Web-based integrated information retrieval performance evaluation platform. It offers a number of metrics that are popular within the scientific community, so as to compose an efficient framework for implementing performance evaluation. We discuss the functionality of RETRIEVAL by citing important aspects such as the data input approaches, the user-level performance metrics parameterization, the evaluation scenarios, the interactive plots, and the performance reports repository that offers both archiving and download functionalities.
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2016 Digital Media Industry & Academic Forum (DMIAF), 2016
The aim of this research is to achieve spatial consistency of the UV map. We present an approach ... more The aim of this research is to achieve spatial consistency of the UV map. We present an approach to produce a fully spatially consistent UV mapping based on the planar parameterisation of the mesh. We apply our method on a 3D digital replica of an ancient Greek Lekythos vessel. We parameterise the mesh of a 3D model onto a unit square 2D plane using computational conformal geometry techniques. The proposed method is genus independent, due to an iterative 3D mesh cutting procedure. Having now the texture of a 3D model depicted on a spatially continuous two dimensional structure enables us to efficiently apply a vast range of image processing based techniques and algorithms.
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2017 14th IAPR International Conference on Document Analysis and Recognition (ICDAR), 2017
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2020 IEEE International Joint Conference on Biometrics (IJCB), 2020
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Pattern Recognition, 2016
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2016 15th International Conference on Frontiers in Handwriting Recognition (ICFHR), 2016
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The Visual Computer, May 2, 2016
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Pattern Recognition, Apr 1, 2016
The problem of facial expression recognition in dynamic sequences of 3D face scans has received a... more The problem of facial expression recognition in dynamic sequences of 3D face scans has received a significant amount of attention in the recent past whereas the problem of retrieval in this type of data has not. A novel retrieval methodology for such data is introduced in this paper. The proposed methodology automatically detects specific facial landmarks and uses them to create a descriptor. This descriptor is the concatenation of three sub-descriptors which capture topological as well as geometric information of the 3D face scans. The motivation behind the proposed hybrid facial expression descriptor is the fact that some facial expressions, like happiness and surprise, are characterized by obvious changes in the mouth topology while others, like anger, fear and sadness, produce geometric but no significant topological changes. The proposed retrieval scheme exploits the Dynamic Time Warping technique in order to compare descriptors corresponding to different 3D facial sequences. A detailed evaluation of the introduced retrieval scheme is presented showing that it outperforms previous state-of-the-art retrieval schemes. Experiments have been conducted using the six prototypical expressions of the standard dataset BU-4DFE and the eight prototypical expressions of the recently available dataset BP4D-Spontaneous. Finally, a majority voting scheme based on the retrieval results is used to achieve unsupervised dynamic 3D facial expression recognition. The achieved classification accuracy is comparable to the state-of-the-art supervised dynamic 3D facial expression recognition techniques. HighlightsWe illustrate a novel retrieval methodology for dynamic sequences of 3D face scans.We present a detailed evaluation of the introduced retrieval scheme.BU-4DFE and BP4D-Spontaneous data sets were used for experiments.Retrieval results are used to achieve unsupervised facial expression recognition.The presented results outperform state-of-the-art retrieval schemes.
Bookmarks Related papers MentionsView impact
International Journal of Image and Graphics, Jul 1, 2019
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Despite numerous recent efforts, 3D object retrieval based on partial shape queries remains a cha... more Despite numerous recent efforts, 3D object retrieval based on partial shape queries remains a challenging problem, far from being solved. The problem can be defined as: given a partial view of a shape as query, retrieve all partially similar 3D models from a repository. The objective of this track is to evaluate the performance of partial 3D object retrieval methods, for partial shape queries of various scan qualities and degrees of partiality. The retrieval problem is often found in cultural heritage applications, for which partial scans of objects query a dataset of geometrically distinct classes.
Bookmarks Related papers MentionsView impact