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Konstantinos Zagoris

dblp:20/5682 · DBLP profile ↗
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24ranked-venue papers
9as first author
0since 2021 · last 2019
0000-0002-3413-9751ORCID · corroborated

Domains — the database's venue-derived domains; a paper can count in several

Databases, data management, data science and information retrieval · 10 · 2 first-authorGraphics, computer vision, multimedia, augmented reality and games · 10 · 5 first-authorArtificial intelligence and machine learning · 8 · 4 first-author

Expertise — from the expertise taxonomy: the topics of the expert's papers under the CCF categories. A weight counts papers with recency: 1 for a paper about the topic, 0.3 when the topic is its context, halved every five years.

Computer graphics and multimedia
1 paper
Image and video processing · 100%
Databases, data mining, and information retrieval
2 papers
Information retrieval · 100%

Topics — the 7 heaviest of 8, each with the papers that count most for it

TopicWeightPapersLastEvidence papers
Image and video processing
document image analysis
0.312017
Unsupervised Word Spotting in Historical Handwritten Document Images Using Document-Oriented Local Features · IEEE Trans. Image Process. 2017
Image and video processing › document image analysis › text recognition
word spotting
0.312017
Unsupervised Word Spotting in Historical Handwritten Document Images Using Document-Oriented Local Features · IEEE Trans. Image Process. 2017
Information retrieval › image retrieval › image representation
bag-of-visual-words
0.112011
Bag-of-visual-words vs global image descriptors on two-stage multimodal retrieval · SIGIR 2011
Information retrieval › image retrieval
content-based image retrieval
0.112011
Bag-of-visual-words vs global image descriptors on two-stage multimodal retrieval · SIGIR 2011
Information retrieval
evaluation
0.112011
The TREC files: the (ground) truth is out there · SIGIR 2011
Information retrieval
multimodal retrieval
0.112011
Bag-of-visual-words vs global image descriptors on two-stage multimodal retrieval · SIGIR 2011
Information retrieval › multi-stage retrieval
two-stage retrieval
0.112011
Bag-of-visual-words vs global image descriptors on two-stage multimodal retrieval · SIGIR 2011

Methods — techniques the papers use, named apart from their topics

spatial context · 0.3segmentation-free matching · 0.3keypoint matching · 0.3document-oriented local features · 0.3text pre-filtering · 0.1statistical significance testing · 0.1global image descriptors · 0.1
YearPublicationVenuePosition
2019 ICDAR 2019 Competition on Document Image Binarization (DIBCO 2019)
abstract
DIBCO 2019 is the international Competition on Document Image Binarization organized in conjunction with the ICDAR 2019 conference. The general objective of the contest is to identify current advances in document image binarization of machine-printed and handwritten document images using performance evaluation measures that are motivated by document image analysis and recognition requirements. This paper describes the competition details including the evaluation measures used as well as the performance of the 24 submitted methods along with a brief description of each method.
Ioannis Pratikakis, Konstantinos Zagoris, Xenofon Karagiannis, Lazaros T. Tsochatzidis, Tanmoy Mondal, Isabelle Marthot-Santaniello
ICDAR2
2018 ICFHR 2018 Competition on Handwritten Document Image Binarization (H-DIBCO 2018)
abstract
H-DIBCO 2018 is the international Handwritten Document Image Binarization Contest organized in the context of ICFHR 2018 conference. The general objective of the contest is to record recent advances in document image binarization using established evaluation performance measures. This paper describes the contest details including the evaluation measures used as well as the performance of the 8 submitted methods along with a brief description of each method.
Ioannis Pratikakis, Konstantinos Zagoris, Panagiotis Kaddas, Basilios Gatos
ICFHR2
2017 ICDAR2017 Competition on Document Image Binarization (DIBCO 2017)
abstract
DIBCO 2017 is the international Competition on Document Image Binarization organized in conjunction with the ICDAR 2017 conference. The general objective of the contest is to identify current advances in document image binarization of machine-printed and handwritten document images using performance evaluation measures that are motivated by document image analysis and recognition requirements. This paper describes the competition details including the evaluation measures used as well as the performance of the 26 submitted methods along with a brief description of each method.
Ioannis Pratikakis, Konstantinos Zagoris, George Barlas, Basilios Gatos
ICDAR2
2017 Bio-Inspired Modeling for the Enhancement of Historical Handwritten Documents
abstract
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.
Konstantinos Zagoris, Ioannis Pratikakis
ICDAR1
2017 Computer-aided diagnosis of mammographic masses based on a supervised content-based image retrieval approach
Lazaros T. Tsochatzidis, Konstantinos Zagoris, Nikolaos Arikidis, Anna Karahaliou, Lena Costaridou, Ioannis Pratikakis
Pattern Recognit.2
2017 Unsupervised Word Spotting in Historical Handwritten Document Images Using Document-Oriented Local Features
abstract
Word spotting strategies employed in historical handwritten documents face many challenges due to variation in the writing style and intense degradation. In this paper, a new method that permits effective word spotting in handwritten documents is presented that it relies upon document-oriented local features, which take into account information around representative keypoints as well a matching process that incorporates spatial context in a local proximity search without using any training data. Experimental results on four historical handwritten data sets for two different scenarios (segmentation-based and segmentation-free) using standard evaluation measures show the improved performance achieved by the proposed methodology.
Konstantinos Zagoris, Ioannis Pratikakis, Basilios Gatos
IEEE Trans. Image Process.1
2016 An Adaptive Zoning Technique for Word Spotting Using Dynamic Time Warping
abstract
Zoning features have been proved one of the most efficient statistical features which provide high speed and low complexity word matching. They are calculated by the density of pixels or pattern characteristics in several zones that the pattern frame is divided. In this paper, an adaptive zoning technique for efficient word spotting is introduced. The main idea is that the zoning features are extracted after cutting the query word in vertical zones, according to its length and pixel distribution along the horizontal axis, and adjusting these boundaries optimally with the corresponding zones in the candidate match-word using Dynamic Time Warping (DTW). This adjustment is performed by coupling every zone of the query word to the corresponding zone of each candidate match-word with the use of the corresponding warping matrix. This process absorbs the ambiguities between the query and the candidate match words and due to this fact it can be applied to both machine-printed and handwritten document images. The proposed word spotting technique is tested using the pixel density as a characteristic feature in every zone and an improvement is recorded compared to other state-of-the-art methods.
A. Papandreou, Basilios Gatos, Konstantinos Zagoris
DAS3
2016 ICFHR2016 Handwritten Document Image Binarization Contest (H-DIBCO 2016)
abstract
H-DIBCO 2016 is the international Handwritten Document Image Binarization Contest organized in the context of ICFHR 2016 conference. The general objective of the contest is to identify current advances in document image binarization of handwritten document images using performance evaluation measures that are motivated by document image analysis and recognition requirements. This paper describes the contest details including the evaluation measures used as well as the performance of the 12 submitted methods along with a brief description of each method.
Ioannis Pratikakis, Konstantinos Zagoris, George Barlas, Basilios Gatos
ICFHR2
2016 ICFHR2016 Handwritten Keyword Spotting Competition (H-KWS 2016)
abstract
The H-KWS 2016, organized in the context of the ICFHR 2016 conference aims at setting up an evaluation framework for benchmarking handwritten keyword spotting (KWS) examining both the Query by Example (QbE) and the Query by String (QbS) approaches. Both KWS approaches were hosted into two different tracks, which in turn were split into two distinct challenges, namely, a segmentation-based and a segmentation-free to accommodate different perspectives adopted by researchers in the KWS field. In addition, the competition aims to evaluate the submitted training-based methods under different amounts of training data. Four participants submitted at least one solution to one of the challenges, according to the capabilities and/or restrictions of their systems. The data used in the competition consisted of historical German and English documents with their own characteristics and complexities. This paper presents the details of the competition, including the data, evaluation metrics and results of the best run of each participating methods.
Ioannis Pratikakis, Konstantinos Zagoris, Basilios Gatos, Joan Puigcerver, Alejandro H. Toselli, Enrique Vidal 0001
ICFHR2
2014 ICFHR 2014 Competition on Handwritten Keyword Spotting (H-KWS 2014)
abstract
H-KWS 2014 is the Handwritten Keyword Spotting Competition organized in conjunction with ICFHR 2014 conference. The main objective of the competition is to record current advances in keyword spotting algorithms using established performance evaluation measures frequently encountered in the information retrieval literature. The competition comprises two distinct tracks, namely, a segmentation-based and a segmentation-free track. Five (5) distinct research groups have participated in the competition with three (3) methods for the segmentation-based track and four (4) methods for the segmentation-free track. The benchmarking datasets that were used in the contest contain both historical and modern documents from multiple writers. In this paper, the contest details are reported including the evaluation measures and the performance of the submitted methods along with a short description of each method.
Ioannis Pratikakis, Konstantinos Zagoris, Basilios Gatos, Georgios Louloudis, Nikolaos Stamatopoulos
ICFHR2
2014 Segmentation-Based Historical Handwritten Word Spotting Using Document-Specific Local Features
abstract
Many word spotting strategies for the modern documents are not directly applicable to historical handwritten documents due to writing styles variety and intense degradation. In this paper, a new method that permits effective word spotting in handwritten documents is presented that relies upon document-specific local features which take into account texture information around representative key points. Experimental work on two historical handwritten datasets using standard evaluation measures shows the improved performance achieved by the proposed methodology.
Konstantinos Zagoris, Ioannis Pratikakis, Basilios Gatos
ICFHR1
2014 Distinction between handwritten and machine-printed text based on the bag of visual words model
Konstantinos Zagoris, Ioannis Pratikakis, Apostolos Antonacopoulos, Basilios Gatos, Nikos Papamarkos
Pattern Recognit.1
2013 Text Detection in Natural Images Using Bio-inspired Models
abstract
Textual information in images constitutes a very rich source of high-level semantics for multimedia indexing and retrieval. In this paper, a new approach is proposed for detecting text in natural images inspired by the properties of the Human Visual System (HVS). In particular, the detection is based upon the functionality of the OFF and ON center-surround cells of the HVS. Cells are combined at different scales to guide a both efficient and effective algorithm. Performance evaluation relies on the ICDAR 2011 Robust Reading Dataset.
Konstantinos Zagoris, Ioannis Pratikakis
ICDAR1
2013 Dynamic two-stage image retrieval from large multimedia databases
Avi Arampatzis, Konstantinos Zagoris, Savvas A. Chatzichristofis
Inf. Process. Manag.2
2012 Handwritten and Machine Printed Text Separation in Document Images Using the Bag of Visual Words Paradigm
abstract
In a number of types of documents, ranging from forms to archive documents and books with annotations, machine printed and handwritten text may be present in the same document image, giving rise to significant issues within a digitisation and recognition pipeline. It is therefore necessary to separate the two types of text before applying different recognition methodologies to each. In this paper, a new approach is proposed which strives towards identifying and separating handwritten from machine printed text using the Bag of Visual Words paradigm (BoVW). Initially, blocks of interest are detected in the document image. For each block, a descriptor is calculated based on the BoVW. The final characterization of the blocks as Handwritten, Machine Printed or Noise is made by a Support Vector Machine classifier. The promising performance of the proposed approach is shown by using a consistent evaluation methodology which couples meaningful measures along with a new dataset.
Konstantinos Zagoris, Ioannis Pratikakis, Apostolos Antonacopoulos, Basilios Gatos, Nikos Papamarkos
ICFHR1
2012 A Fuzzy Rank-Based Late Fusion Method for Image Retrieval
Savvas A. Chatzichristofis, Konstantinos Zagoris, Yiannis S. Boutalis, Avi Arampatzis
MMM2
2011 Dynamic Two-Stage Image Retrieval from Large Multimodal Databases
Avi Arampatzis, Konstantinos Zagoris, Savvas A. Chatzichristofis
ECIR2
2011 Fusion vs. Two-Stage for Multimodal Retrieval
Avi Arampatzis, Konstantinos Zagoris, Savvas A. Chatzichristofis
ECIR2
2011 Bag-of-visual-words vs global image descriptors on two-stage multimodal retrieval
abstract
The Bag-Of-Visual-Words (BOVW) paradigm is fast becoming a popular image representation for Content-Based Image Retrieval (CBIR), mainly because of its better retrieval effectiveness over global feature representations on collections with images being near-duplicate to queries. In this experimental study we demonstrate that this advantage of BOVW is diminished when visual diversity is enhanced by using a secondary modality, such as text, to pre-filter images.
Savvas A. Chatzichristofis, Konstantinos Zagoris, Avi Arampatzis
SIGIR2
2011 The TREC files: the (ground) truth is out there
abstract
Traditional tools for information retrieval (IR) evaluation, such as TREC's trec_eval, have outdated command-line interfaces with many unused features, or 'switches', accumulated over the years. They are usually seen as cumbersome applications by new IR researchers, steepening the learning curve. We introduce a platform-independent application for IR evaluation with a graphical easy-to-use interface: the TREC_Files Evaluator. The application supports most of the standard measures used for evaluation in TREC, CLEF, and elsewhere, such as MAP, P10, P20, and bpref, as well as the Averaged Normalized Modified Retrieval Rank (ANMRR) proposed by MPEG for image retrieval evaluation. Additional features include a batch mode and statistical significance testing of the results against a pre-selected baseline.
Savvas A. Chatzichristofis, Konstantinos Zagoris, Avi Arampatzis
SIGIR2
2011 Image retrieval systems based on compact shape descriptor and relevance feedback information
Konstantinos Zagoris, Ergina Kavallieratou, Nikos Papamarkos
J. Vis. Commun. Image Represent.1
2010 A Document Image Retrieval System
Konstantinos Zagoris, Ergina Kavallieratou, Nikos Papamarkos
Eng. Appl. Artif. Intell.1
2010 Accurate Image Retrieval Based on Compact Composite Descriptors and Relevance Feedback Information
abstract
In this paper a new set of descriptors appropriate for image indexing and retrieval is proposed. The proposed descriptors address the tremendously increased need for efficient content-based image retrieval (CBIR) in many application areas such as the Internet, biomedicine, commerce and education. These applications commonly store image information in large image databases where the image information cannot be accessed or used unless the database is organized to allow efficient storage, browsing and retrieval. To be applicable in the design of large image databases, the proposed descriptors are compact, with the smallest requiring only 23 bytes per image. The proposed descriptors' structure combines color and texture information which are extracted using fuzzy approaches. To evaluate the performance of the proposed descriptors, the objective Average Normalized Modified Retrieval Rank (ANMRR) is used. Experiments conducted on five benchmarking image databases demonstrate the effectiveness of the proposed descriptors in outperforming other state-of-the-art descriptors. Also, a Auto Relevance Feedback (ARF) technique is introduced which is based on the proposed descriptors. This technique readjusts the initial retrieval results based on user preferences improving the retrieval score significantly. An online demo of the image retrieval system img(Anaktisi) that implements the proposed descriptors can be found at .
Savvas A. Chatzichristofis, Konstantinos Zagoris, Yiannis S. Boutalis, Nikos Papamarkos
Int. J. Pattern Recognit. Artif. Intell.2
2006 Web Document Image Retrieval System Based on Word Spotting
abstract
Nowadays, the huge non-indexing quantities of image archives (especially document images) require the development of intelligent tools for their retrieval with convenience comparable of the texts search engines. The proposed technique addresses the document retrieval problem by a word matching procedure. It performs matching directly in the images bypassing OCR and using word-images as queries. It is constituted of two different parts: The offline and the online operation. In the offline operation, the archive of document images is examined and the results are stored in a database. The online operation consists of the Web interface, the creation of the word's image and finally, the matching stage. The proposed matching process it can be described shortly as a two-threshold rating system. Finally, the proposed system has been build and it can be found in at the Web address: http://orpheus.ee.duth.gr/irs2.
Konstantinos Zagoris, Nikos Papamarkos, Christodoulos Chamzas
ICIP1