Giorgos Sfikas Assistant Professor

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Publications




Peer-reviewed (Conferences, Journals, Book Chapters)


  • [C1] G.Sfikas, C.Constantinopoulos, A.Likas, N.P.Galatsanos: "An Analytic Distance Metric for Gaussian Mixture Models with Application in Image Retrieval", International conference on Artificial Neural Networks (ICANN), Warsaw, Poland, September 2005 [pdf] [code]
  • [C2] G.Sfikas, C.Nikou, N.P.Galatsanos: "Robust image segmentation with mixtures of Student's t-distributions", IEEE International conference on Image Processing (ICIP), San Antonio, USA, September 2007   [pdf] [code]
  • [C3] G.Sfikas, C.Nikou, N.P.Galatsanos: "Edge-preserving spatially-varying mixtures for image segmentation", IEEE Computer Vision and Pattern Recognition (CVPR), Anchorage, USA, June 2008   *Selected for oral presentation (top 3% of accepted papers)* [pdf] [code]
  • [C4] G.Sfikas, C.Nikou, N.P.Galatsanos, C.Heinrich: "MR Brain Tissue classification using an edge-preserving spatially variant Bayesian mixture model", 11th international conference on medical image computing and computer assisted intervention (MICCAI), New York, USA, September 2008  [pdf] [code]
  • [C5] G.Sfikas, C.Nikou, C.Heinrich, N.P.Galatsanos: "On optimization of probability vector random fields used for image segmentation", IEEE International workshop on Machine Learning for Signal Processing (MLSP), Grenoble, France, September 2009  [pdf]
  • [C6] G.Sfikas, C.Heinrich, J.Zallat, C.Nikou, N.P.Galatsanos: "Joint recovery and segmentation of polarimetric images using a compound MRF and mixture modeling", International Conference on Image processing (ICIP), Cairo, Egypt, November 2009  [pdf] [code]
  • [C7] G.Sfikas, C.Heinrich, C.Nikou: "Multiple atlas inference and population analysis with spectral clustering", IEEE International Conference on Pattern Recognition (ICPR), Istanbul, Turkey, August 2010  [pdf]
  • [C8] G.Sfikas, C.Nikou, N.P.Galatsanos, C.Heinrich: "Majorization-Minimization mixture model determination in image segmentation", IEEE Computer Vision and Pattern recognition (CVPR), Colorado Springs, USA, June 2011  [pdf]
  • [C9] A.P.Giotis, G.Sfikas, C.Nikou, B.Gatos: "Shape-based Word Spotting in Handwritten Document Images", International Conference on Document Analysis and Recognition (ICDAR), Nancy, France, August 2015   [pdf]
  • [C10] B.Gatos, N.Stamatopoulos, G.Louloudis, G.Sfikas, G.Retsinas, F.Simistira, V.Papavassiliou, V.Katsouros: "GRPOLY-DB: An old Greek polytonic document image database", International Conference on Document Analysis and Recognition (ICDAR), Nancy, France, August 2015  [pdf] [dataset]
  • [C11] G.Sfikas, A.P.Giotis, G.Louloudis, B.Gatos: "Using Attributes for Word Spotting and Recognition in Polytonic Greek Documents", International Conference on Document Analysis and Recognition (ICDAR), Nancy, France, August 2015  [pdf]
  • [C12] G.Louloudis, G.Sfikas, N.Stamatopoulos, B.Gatos: "Word Segmentation using the Student's-t Distribution", International Workshop on Document Analysis and Systems (DAS), Santorini, Greece, April 2016  [pdf] [code]
  • [C13] G.Sfikas, C.Akasiadis, E.Spyrou: "Creating a smart room using an IoT approach", Workshop on Artificial Intelligence and Internet of Things (AI-IoT), in conjunction with the 9th Hellenic Conference on Artificial Intelligence (SETN), Thessaloniki, Greece, May 2016  [pdf]
  • [C14] G.Sfikas, G.Louloudis, N.Stamatopoulos, B.Gatos: "Bayesian mixture models on connected components for Newspaper article segmentation", ACM Symposium on Document Engineering (DocEng), Vienna, Austria, September 2016  [pdf]
  • [C15] G.Sfikas, G.Retsinas, B.Gatos: "Zoning Aggregated Hypercolumns for Keyword Spotting", International Conference on Frontiers in Handwriting Recognition (ICFHR), Shenzhen, China, October 2016   [pdf] [code]
  • [C16] G.Sfikas, C.Nikou: "Bayesian Multiview Manifold Learning applied to Hippocampus Shape and Clinical Score Data", 3rd workshop on Bayesian and Graphical Models in Biomedical Imaging, held in conjunction with the 19th International Conference on Medical Image Computing and Computer Assisted Intervention (MICCAI), Athens, Greece, October 2016   *Best paper award*   [pdf]
  • [C17] G.Retsinas, G.Sfikas, B.Gatos: "Transferable Deep Features for Keyword Spotting", International Workshop on Computational Intelligence for Multimedia Understanding, held in conjunction with the 25th European Signal Processing Conference (EUSIPCO), Kos, Greece, September 2017   [pdf]
  • [C18] G.Sfikas, B.Gatos, C.Nikou: "SemiCCA: A New Semi-Supervised Probabilistic CCA Model for Keyword Spotting", IEEE International Conference on Image processing (ICIP), Beijing, China, September 2017   [pdf]
  • [C19] G.Retsinas, G.Louloudis, N.Stamatopoulos, G.Sfikas, B.Gatos, "Nonlinear Manifold Embedding on Keyword Spotting using t-SNE", International Conference on Document Analysis and Recognition (ICDAR), Kyoto, Japan, November 2017   [pdf]
  • [C20] G.Sfikas, G.Retsinas, B.Gatos: "A PHOC Decoder for Lexicon-free Handwriting Word Recognition", International Conference on Document Analysis and Recognition (ICDAR), Kyoto, Japan, November 2017   [pdf]
  • [C21] G.Retsinas, G.Sfikas, N.Stamatopoulos, G.Louloudis, B.Gatos: "Exploring critical aspects of CNN-based keyword spotting. A PHOCNet study", International Workshop on Document Analysis and Systems (DAS), Vienna, Austria, April 2018   [pdf]
  • [C22] G.Retsinas, G.Sfikas, G.Louloudis, N.Stamatopoulos, B.Gatos, “Compact deep descriptors for keyword spotting”, International Conference on Frontiers in Handwriting Recognition (ICFHR), Niagara Falls, USA, August 2018   [pdf]
  • [C23] M.Plissiti, P.Dimitrakopoulos, G.Sfikas, C.Nikou, O.Krikoni, A.Charchanti, “SIPAKMED: A new dataset for feature and image-based classification of normal and pathological cervical cells in Pap smear images”, IEEE International Conference on Image Processing (ICIP), Athens, Greece, October 2018   [pdf] [dataset]
  • [C24] G.Retsinas, G.Louloudis, N.Stamatopoulos, G.Sfikas, B.Gatos, “An Alternative Deep Feature Approach to Line Level Keyword Spotting”, IEEE Computer Vision and Pattern recognition (CVPR), Long Beach (CA), USA, June 2019   [pdf]
  • [C25] G.Sfikas, A.Noula, J.Patacas, D.Ioannidis, D.Tzovaras, "Building thermal output determination using visible spectrum and infrared inputs", International Conference on Energy and Sustainable Futures (ICESF), Nottingham, United Kingdom, September 2019   [pdf]
  • [C26] P.Kouzouglidis, G.Sfikas, C.Nikou, "Automatic Video Colorization using 3D Conditional Generative Adversarial Networks", International Symposium on Visual Computing (ISVC), Lake Tahoe (NV), USA, October 2019   [pdf] [example colorizations]
  • [C27] P.Dimitrakopoulos, G.Sfikas, C.Nikou, "Nuclei Detection Using Residual Attention Feature Pyramid Networks", IEEE International Conference on Bioinformatics and Bioengineering (BIBE), Athens, Greece, October 2019   *Best student paper award*   [pdf]
  • [C28] G.Sfikas, J.Patacas, C.Psarros, A.Noula, D.Ioannidis, D.Tzovaras, "A Deep Neural Network-based method for the detection and accurate thermography statistics estimation of aerially surveyed structures", International Conference on Construction Applications of Virtual Reality (CONVR), Bangkok, Thailand, November 2019   [pdf]
  • [C29] P.Dimitrakopoulos, G.Sfikas, C.Nikou, "Ising-GAN: Annotated Data Augmentation with a spatially constrained Generative Adversarial Network", IEEE International Symposium on Biomedical Imaging (ISBI), April 2020   [pdf]
  • [C30] P.Dimitrakopoulos, G.Sfikas, C.Nikou, "WInD: Wasserstein Inception Distance for Evaluating Generative Adversarial Network Performance", IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), May 2020   [pdf] [code]
  • [C31] G.Sfikas, D.Ioannidis, D.Tzovaras, "Quaternionic keypoint description for multispectral imaging", Hellenic Conference on Artificial Intelligence (SETN), September 2020   [pdf]
  • [C32] G.Sfikas, D.Ioannidis, D.Tzovaras, "Quaternion Harris for Multispectral Keypoint Detection", IEEE International conference on Image Processing (ICIP), October 2020   [pdf]
  • [C33] V.Megir, G.Sfikas, A.Mekras, C.Nikou, D.Ioannidis, D.Tzovaras, "Salient object detection with pretrained Deeplab and k-means: Application to UAV-captured building imagery", 1st workshop on Pattern Recognition and Automation in Construction and the Built Environment (PRAConBE 2020), held in conjunction with the 25th International Conference on Pattern Recognition (ICPR), January 2021   [pdf]
  • [C34] G.Sfikas, A.P.Giotis, G.Retsinas, C.Nikou, "Quaternion Generative Adversarial Networks for Inscription Detection in Byzantine Monuments", 2nd workshop on Pattern Recognition for Cultural Heritage (PatReCH 2020), held in conjunction with the 25th International Conference on Pattern Recognition (ICPR), January 2021   [pdf] [code]
  • [C35] G.Retsinas, G.Sfikas, C.Nikou, "Iterative Weighted Transductive Learning for Handwriting Recognition", International Conference on Document Analysis and Recognition (ICDAR), Lausanne, Switzerland, September 2021   [pdf]
  • [C36] G.Retsinas, G.Sfikas, C.Nikou, P.Maragos, "Deformation-invariant Networks for Handwritten Text Recognition", IEEE International Conference on Image processing (ICIP), Anchorage, USA, September 2021   [pdf] [code]
  • [C37] G.Retsinas, G.Sfikas, C.Nikou, P.Maragos, "From Seq2Seq Recognition to Handwritten Word Embeddings", British Machine Vision Conference (BMVC), held online, November 2021   [pdf] [supplemental material] [code]
  • [C38] B.Gatos, G.Sfikas, P.Kaddas, G.Retsinas, "CULDILE: Cultural Dimensions of Deep Learning, A Document Analysis System for Historical Documents", International Workshop on Document Analysis and Systems (DAS), La Rochelle, France, May 2022   [pdf]
  • [C39] G.Sfikas, G.Retsinas, B.Gatos, "Exploring uses of Normalizing Flows for Document Image Processing: Text Super-resolution and Binarization", International Workshop on Document Analysis and Systems (DAS), La Rochelle, France, May 2022   [pdf]
  • [C40] G.Sfikas, G.Retsinas, A.P.Giotis, B.Gatos, C.Nikou, "Keyword Spotting with Quaternionic ResNet: Application to Spotting in Greek Manuscripts", International Workshop on Document Analysis and Systems (DAS), La Rochelle, France, May 2022   [pdf]
  • [C41] G.Retsinas, G.Sfikas, B.Gatos, C.Nikou, "Best Practices for a Handwritten Text Recognition system", International Workshop on Document Analysis and Systems (DAS), La Rochelle, France, May 2022   [pdf]
  • [C42] G.Retsinas, G.Sfikas, B.Gatos, C.Nikou, "On-The-Fly Deformations for Keyword Spotting", International Workshop on Document Analysis and Systems (DAS), La Rochelle, France, May 2022   [pdf]
  • [C43] G.Sfikas, G.Retsinas, B.Gatos, C.Nikou, "Hypercomplex Generative Adversarial Networks for Lightweight Semantic Labeling", International Conference on Pattern Recognition and Artificial Intelligence (ICPRAI), Paris, France, June 2022   [pdf]
  • [C44] A.P.Giotis, G.Sfikas, C.Nikou, "Adversarial deep features for weakly supervised document image keyword spotting", IEEE Image, Video, and Multidimensional Signal Processing Workshop (IVMSP), Nafplio, Greece, June 2022
  • [C45] A.Katsaliros, I.Panagos, G.Sfikas, C.Nikou, "Road Crack Detection Using Quaternion Neural Networks", IEEE Image, Video, and Multidimensional Signal Processing Workshop (IVMSP), Nafplio, Greece, June 2022   [pdf]
  • [C46] P.Dimitrakopoulos, G.Sfikas, C.Nikou, "Variational Feature Pyramid Networks", International Conference on Machine Learning (ICML), Baltimore, USA, July 2022   [pdf]
  • [C47] I.Panagos, G.Sfikas, C.Nikou, "Compressing Audio Visual Speech Recognition Models With Parameterized Hypercomplex Layers", Hellenic Conference on Artificial Intelligence (SETN), September 2022*
  • [C48] G.Retsinas, G.Sfikas, P.P.Filntisis, P.Maragos, "Newton-based Trainable Learning Rate", IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), June 2023   [pdf] [code]
  • [C49] G.Retsinas, G.Sfikas, C.Nikou, "Keyword Spotting Simplified: A Segmentation-Free Approach using Character Counting and CTC re-scoring", International Conference on Document Analysis and Recognition (ICDAR), San Jose, USA, August 2023
  • [C50] G.Sfikas, G.Retsinas, P.Dimitrakopoulos, B.Gatos, C.Nikou, "Shared-Operation Hypercomplex Networks for Handwritten Text Recognition", International Conference on Document Analysis and Recognition (ICDAR), San Jose, USA, August 2023
  • [C51] K.Nikolaidou, G.Retsinas, V.Christlein, M.Seuret, G.Sfikas, E.B.Smith, H.Mokayed, M.Liwicki, "Styled Text-to-Text-Content-Image Generation with Latent Diffusion Models", International Conference on Document Analysis and Recognition (ICDAR), San Jose, USA, August 2023
  • [C52] G.Sfikas, G.Retsinas, B.Gatos, "Document Binarization with Quaternionic Double Discriminator Generative Adversarial Network", International Conference on Document Analysis and Recognition - Workshop on Machine Learning (ICDAR-WML), San Jose, USA, August 2023
  • [C53] P.Dimitrakopoulos, G.Sfikas, C.Nikou, "Implicit Neural Representation Inference for Low-Dimensional Bayesian Deep Learning", International Conference on Learning Representations (ICLR), Vienna, Austria, May 2024

  • [J1] G.Sfikas, C.Nikou, N.P.Galatsanos, C.Heinrich: "Spatially varying mixtures incorporating line processes for image segmentation", Journal of Mathematical Imaging and Vision ,vol. 36(2), pp. 91-110, 2010   [pdf] [code]
  • [J2] G.Sfikas, C.Heinrich, J.Zallat, C.Nikou, N.P.Galatsanos: "Recovery of polarimetric Stokes images by spatial mixture models", Journal of the Optical Society of America A , vol. 28(3), pp. 465-474, 2011   [pdf] [code]
  • [J3] N.Philippi, V.Noblet, A.Botzung, O.Després, F.Renard, G.Sfikas, B.Cretin, S.Kremer, L.Manning, F.Blanc: "MRI-based volumetry correlates of autobiographical memory in Alzheimer's disease", PLOS ONE, vol. 7(10), pp. e46200, 2012   [pdf]
  • [J4] S.Faisan, C.Heinrich, G.Sfikas, J.Zallat: "Estimation of Mueller matrices using non-local means filtering", Optics Express, vol. 21(4), pp. 4424-4438, 2013   [pdf]
  • [J5] A.P.Giotis, G.Sfikas, B.Gatos, C.Nikou: "A survey of document image word spotting techniques", Pattern Recognition, vol.68, pp. 310-332, 2017   [pdf]
  • [J6] K.Papadimitriou, G.Sfikas, C.Nikou: "Tomographic Image Reconstruction with a Spatially Varying Gamma Mixture Prior", Journal of Mathematical Imaging and Vision, vol. 60(8), pp. 1355-1365, 2018  
  • [J7] G. Muehlberger, L.Seaward, M. Terras, S. Ares Oliveira, V. Bosch, B. Vicente, C. Maximilian, S. Colutto, H. Déjean, M. Diem, S. Fiel, B. Gatos, T. Grüning, A. Greinoecker, G. Hackl, V. Haukkovaara, G. Heyer, L. Hirvonen, T. Hodel, M. Jokinen, P. Kahle, M. Kallio, F. Kaplan, F. Kleber, R. Labahn, E.M. Lang, S. Laube, G. Leifert, G. Louloudis, R. McNicholl, JL Meunier, J. Michael, EP Mühlbauer, N. ElenaPhilipp, I. Pratikakis, J.P.Puigcerver, H.Putz, G. Retsinas, V. Romero, R. Sablatnig, JA. Sánchez, P. Schofield, G. Sfikas, C. Sieber, N. Stamatopoulos, T. Strauss, T. Terbul, A. Toselli, B. Ulreich, M. Villegas, E. Vidal, JW. Walcher, M. Weidemann, H. Wurster, K. Zagoris, "Transforming Scholarship in the Archives Through Handwritten Text Recognition: Transkribus as a Case Study", Journal of Documentation, vol. 75(5), pp. 954-976., 2019  
  • [J8] G. Tsigkas, G. Sfikas, A. Pasialis, A. Vlachopoulos, C. Nikou: "Markerless detection of ancient rock carvings in the wild: rock art in Vathy, Astypalaia", Pattern Recognition Letters, vol. 135, pp. 337-345, 2020   [pdf] [dataset]
  • [J9] A. El Saer, L. Grammatikopoulos, G. Sfikas, G. Karras, E. Petsa: "A Novel Framework for Image Matching and Stitching for Moving Car Inspection under Illumination Challenges", MDPI Sensors, vol. 24(4), 2024

  • [BC1] B. Gatos, G. Louloudis, N. Stamatopoulos, G. Sfikas: "Historical Document Processing”, in Handwriting: Recognition, Development and Analysis, Editors: Byron Leite, Dantas Bezerra, Cleber Zanchettin, Alejandro H. Toselli and Giuseppe Pirlo, Chapter 3. Nova science publishers, 2017. ISBN 978-1-53611-957-2

Technical reports, tutorials and other non-peer reviewed material

  • [TR1] B.Gatos, G.Louloudis, N.Stamatopoulos, G.Sfikas: "Historical Document Processing", ACM Symposium on Document Engineering (DocEng), Valetta, Malta, September 2017[pdf]
  • [TR2] G.Sfikas: "Mycenean wall-paintings. Case study: The 'Mycenean lady'. Computational methods for prehistoric wall-painting processing and reconstruction", February 2013[pdf] [in Greek]

Theses

  • Bsc thesis: "Μίξεις κανονικών κατανομών για ανάκτηση εικόνας"
    ("Using gaussian mixture models for image retrieval")     [pdf] (in greek)
  • Msc thesis: "Στατιστικές μέθοδοι για ανάκτηση εικόνας με βάση το περιεχόμενο"
    ("Statistical methods for content-based image retrieval")     [pdf] (in greek)
  • Doctoral thesis: "Modèles statistiques non linéaires et non gaussiens compacts pour l'analyse de structures cérébrales"
    ("Statistical non-linear, non-gaussian compact models for brain structure analysis")     [pdf]