Imperial College London

STEFANOS ZAFEIRIOU, PhD

Faculty of EngineeringDepartment of Computing

Reader in Machine Learning and Computer Vision
 
 
 
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Contact

 

+44 (0)20 7594 8461s.zafeiriou Website CV

 
 
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Location

 

375Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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178 results found

Chrysos GG, Zafeiriou S, 2018, (PDT)-T-2: Person-Specific Detection, Deformable Tracking, IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, Vol: 40, Pages: 2555-2568, ISSN: 0162-8828

JOURNAL ARTICLE

Sagonas C, Ververas E, Panagakis Y, Zafeiriou Set al., 2018, Recovering Joint and Individual Components in Facial Data, IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, Vol: 40, Pages: 2668-2681, ISSN: 0162-8828

JOURNAL ARTICLE

Booth J, Roussos A, Ververas E, Antonakos E, Ploumpis S, Panagakis Y, Zafeiriou Set al., 2018, 3D Reconstruction of "In-the-Wild" Faces in Images and Videos., IEEE Trans Pattern Anal Mach Intell, Vol: 40, Pages: 2638-2652

3D Morphable Models (3DMMs) are powerful statistical models of 3D facial shape and texture, and are among the state-of-the-art methods for reconstructing facial shape from single images. With the advent of new 3D sensors, many 3D facial datasets have been collected containing both neutral as well as expressive faces. However, all datasets are captured under controlled conditions. Thus, even though powerful 3D facial shape models can be learnt from such data, it is difficult to build statistical texture models that are sufficient to reconstruct faces captured in unconstrained conditions ("in-the-wild"). In this paper, we propose the first "in-the-wild" 3DMM by combining a statistical model of facial identity and expression shape with an "in-the-wild" texture model. We show that such an approach allows for the development of a greatly simplified fitting procedure for images and videos, as there is no need to optimise with regards to the illumination parameters. We have collected three new benchmarks that combine "in-the-wild" images and video with ground truth 3D facial geometry, the first of their kind, and report extensive quantitative evaluations using them that demonstrate our method is state-of-the-art.

JOURNAL ARTICLE

Wang M, Panagakis Y, Snape P, Zafeiriou SPet al., 2018, Disentangling the Modes of Variation in Unlabelled Data., IEEE Trans Pattern Anal Mach Intell, Vol: 40, Pages: 2682-2695

Statistical methods are of paramount importance in discovering the modes of variation in visual data. The Principal Component Analysis (PCA) is probably the most prominent method for extracting a single mode of variation in the data. However, in practice, several factors contribute to the appearance of visual objects including pose, illumination, and deformation, to mention a few. To extract these modes of variations from visual data, several supervised methods, such as the TensorFaces relying on multilinear (tensor) decomposition have been developed. The main drawbacks of such methods is that they require both labels regarding the modes of variations and the same number of samples under all modes of variations (e.g., the same face under different expressions, poses etc.). Therefore, their applicability is limited to well-organised data, usually captured in well-controlled conditions. In this paper, we propose a novel general multilinear matrix decomposition method that discovers the multilinear structure of possibly incomplete sets of visual data in unsupervised setting (i.e., without the presence of labels). We also propose extensions of the method with sparsity and low-rank constraints in order to handle noisy data, captured in unconstrained conditions. Besides that, a graph-regularised variant of the method is also developed in order to exploit available geometric or label information for some modes of variations. We demonstrate the applicability of the proposed method in several computer vision tasks, including Shape from Shading (SfS) (in the wild and with occlusion removal), expression transfer, and estimation of surface normals from images captured in the wild.

JOURNAL ARTICLE

Chrysos GG, Antonakos E, Zafeiriou S, 2018, IPST: Incremental Pictorial Structures for Model-Free Tracking of Deformable Objects, IEEE TRANSACTIONS ON IMAGE PROCESSING, Vol: 27, Pages: 3529-3540, ISSN: 1057-7149

JOURNAL ARTICLE

Trigeorgis G, Nicolaou MA, Schuller BW, Zafeiriou Set al., 2018, Deep Canonical Time Warping for Simultaneous Alignment and Representation Learning of Sequences, IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, Vol: 40, Pages: 1128-1138, ISSN: 0162-8828

JOURNAL ARTICLE

Booth J, Roussos A, Ponniah A, Dunaway D, Zafeiriou Set al., 2018, Large Scale 3D Morphable Models, INTERNATIONAL JOURNAL OF COMPUTER VISION, Vol: 126, Pages: 233-254, ISSN: 0920-5691

JOURNAL ARTICLE

Chrysos GG, Antonakos E, Snape P, Asthana A, Zafeiriou Set al., 2018, A Comprehensive Performance Evaluation of Deformable Face Tracking "In-the-Wild", INTERNATIONAL JOURNAL OF COMPUTER VISION, Vol: 126, Pages: 198-232, ISSN: 0920-5691

JOURNAL ARTICLE

Kollias D, Tzirakis P, Nicolaou MA, Papaioannou A, Zhao G, Schuller BW, Kotsia I, Zafeiriou Set al., 2018, Deep Affect Prediction in-the-wild: Aff-Wild Database and Challenge, Deep Architectures, and Beyond., CoRR, Vol: abs/1804.10938

JOURNAL ARTICLE

Zafeiriou L, Panagakis Y, Pantic M, Zafeiriou Set al., 2017, Nonnegative Decompositions for Dynamic Visual Data Analysis, IEEE TRANSACTIONS ON IMAGE PROCESSING, Vol: 26, Pages: 5603-5617, ISSN: 1057-7149

JOURNAL ARTICLE

Tzirakis P, Trigeorgis G, Nicolaou MA, Schuller BW, Zafeiriou Set al., 2017, End-to-End Multimodal Emotion Recognition Using Deep Neural Networks, IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING, Vol: 11, Pages: 1301-1309, ISSN: 1932-4553

JOURNAL ARTICLE

Georgakis C, Panagakis Y, Zafeiriou S, Pantic Met al., 2017, The Conflict Escalation Resolution (CONFER) Database, IMAGE AND VISION COMPUTING, Vol: 65, Pages: 37-48, ISSN: 0262-8856

JOURNAL ARTICLE

Sagonas C, Panagakis Y, Zafeiriou S, Pantic Met al., 2017, Robust Statistical Frontalization of Human and Animal Faces, INTERNATIONAL JOURNAL OF COMPUTER VISION, Vol: 122, Pages: 270-291, ISSN: 0920-5691

JOURNAL ARTICLE

Cheng S, Marras I, Zafeiriou S, Pantic Met al., 2017, Statistical non-rigid ICP algorithm and its application to 3D face alignment, IMAGE AND VISION COMPUTING, Vol: 58, Pages: 3-12, ISSN: 0262-8856

JOURNAL ARTICLE

Trigeorgis G, Bousmalis K, Zafeiriou S, Schuller BWet al., 2017, A Deep Matrix Factorization Method for Learning Attribute Representations, IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, Vol: 39, Pages: 417-429, ISSN: 0162-8828

JOURNAL ARTICLE

Chrysos GG, Zafeiriou S, 2017, Deep Face Deblurring, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), Publisher: IEEE, Pages: 2015-2024, ISSN: 2160-7508

CONFERENCE PAPER

Fabris A, Nicolaou MA, Kotsia I, Zafeiriou Set al., 2017, DYNAMIC PROBABILISTIC LINEAR DISCRIMINANT ANALYSIS FOR VIDEO CLASSIFICATION, IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Publisher: IEEE, Pages: 2781-2785, ISSN: 1520-6149

CONFERENCE PAPER

Zafeiriou S, Trigeorgis G, Chrysos G, Deng J, Shen Jet al., 2017, The Menpo Facial Landmark Localisation Challenge: A step towards the solution, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), Publisher: IEEE, Pages: 2116-2125, ISSN: 2160-7508

CONFERENCE PAPER

Wang M, Panagakis Y, Snape P, Zafeiriou Set al., 2017, Learning the Multilinear Structure of Visual Data, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Publisher: IEEE, Pages: 6053-6061, ISSN: 1063-6919

CONFERENCE PAPER

Sagonas C, Panagakis Y, Leidinger A, Zafeiriou Set al., 2017, Robust Joint and Individual Variance Explained, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Publisher: IEEE, Pages: 5739-5748, ISSN: 1063-6919

CONFERENCE PAPER

Trigeorgis G, Snape P, Kokkinos I, Zafeiriou Set al., 2017, Face Normals "in-the- wild" using Fully Convolutional Networks, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Publisher: IEEE, Pages: 340-349, ISSN: 1063-6919

CONFERENCE PAPER

Booth J, Antonakos E, Ploumpis S, Trigeorgis G, Panagakis Y, Zafeiriou Set al., 2017, 3D Face Morphable Models "In-the-Wild", 30TH IEEE CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION (CVPR 2017), Pages: 5464-5473, ISSN: 1063-6919

JOURNAL ARTICLE

Guler RA, Trigeorgis G, Antonakos E, Snape P, Zafeiriou S, Kokkinos Iet al., 2017, DenseReg: Fully Convolutional Dense Shape Regression In-the-Wild, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Publisher: IEEE, Pages: 2614-2623, ISSN: 1063-6919

CONFERENCE PAPER

Xue N, Panagakis Y, Zafeiriou S, 2017, Side Information in Robust Principal Component Analysis: Algorithms and Applications, 16th IEEE International Conference on Computer Vision (ICCV), Publisher: IEEE, Pages: 4327-4335, ISSN: 1550-5499

CONFERENCE PAPER

Alabort-i-Medina J, Zafeiriou S, 2017, A Unified Framework for Compositional Fitting of Active Appearance Models, INTERNATIONAL JOURNAL OF COMPUTER VISION, Vol: 121, Pages: 26-64, ISSN: 0920-5691

JOURNAL ARTICLE

Bahri M, Panagakis Y, Zafeiriou S, 2017, Robust Kronecker-Decomposable Component Analysis for Low-Rank Modeling, 16th IEEE International Conference on Computer Vision (ICCV), Publisher: IEEE, Pages: 3372-3381, ISSN: 1550-5499

CONFERENCE PAPER

Tzirakis P, Trigeorgis G, Nicolaou MA, Schuller BW, Zafeiriou Set al., 2017, End-to-End Multimodal Emotion Recognition Using Deep Neural Networks., J. Sel. Topics Signal Processing, Vol: 11, Pages: 1301-1309

JOURNAL ARTICLE

Hovhannisyan V, Parpas P, Zafeiriou S, 2016, MAGMA: Multi-level accelerated gradient mirror descent algorithm for large-scale convex composite minimization, SIAM Journal on Imaging Sciences, Vol: 9, Pages: 1829-1857, ISSN: 1936-4954

Composite convex optimization models arise in several applications, and are especially prevalentin inverse problems with a sparsity inducing norm and in general convex optimization with simpleconstraints. The most widely used algorithms for convex composite models are accelerated first ordermethods, however they can take a large number of iterations to compute an acceptable solution forlarge-scale problems. In this paper we propose to speed up first order methods by taking advantageof the structure present in many applications and in image processing in particular. Our method isbased on multi-level optimization methods and exploits the fact that many applications that giverise to large scale models can be modelled using varying degrees of fidelity. We use Nesterov’sacceleration techniques together with the multi-level approach to achieve an O(1/√ǫ) convergencerate, where ǫ denotes the desired accuracy. The proposed method has a better convergence ratethan any other existing multi-level method for convex problems, and in addition has the same rateas accelerated methods, which is known to be optimal for first-order methods. Moreover, as ournumerical experiments show, on large-scale face recognition problems our algorithm is several timesfaster than the state of the art.

JOURNAL ARTICLE

Panagakis Y, Nicolaou MA, Zafeiriou S, Pantic Met al., 2016, Robust Correlated and Individual Component Analysis, IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, Vol: 38, Pages: 1665-1678, ISSN: 0162-8828

JOURNAL ARTICLE

Snape P, Pszczolkowski S, Zafeiriou S, Tzimiropoulos G, Ledig C, Rueckert Det al., 2016, A robust similarity measure for volumetric image registration with outliers, IMAGE AND VISION COMPUTING, Vol: 52, Pages: 97-113, ISSN: 0262-8856

JOURNAL ARTICLE

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