Page moved!  This web page is no longer updated. I have successfully defended my PhD thesis at NTUA and I have moved to UCLA as a postdoctoral scholar. Please visit my new web home page.

Biosketch

I am a CVSP group member, working towards my PhD in the areas of image analysis, computer vision, and multimodal processing. My PhD thesis advisor is Prof. Petros Maragos. I completed my undergraduate studies in the ECE school of NTUA in 2003, also working for 18 months (2001-2003) as a research assistant at the Institute of Informatics & Telecommunications (IIT), Demokritos National Center for Scientific Research. During the summer of 2006 I visited Prof. Anil Kokaram's Sigmedia group at Trinity College Dublin, Ireland. Here is my CV.

News

I successfully defended my thesis in July 2009 and in October 2009 I moved to UCLA as a postdoctoral fellow, joining Prof. Alan Yuille's group. Please visit my new web home page.

We have recently organized at NTUA a one-day workshop in Athens, whose topic has been digital technologies applied to cultural heritage applications, focusing on Akrotiri, Thera.
[Workshop page...]

Research

My research is in the following areas:

Digital Restoration of Missing Parts in the Pre-historic Wall Paintings of Thera

I have been working on PDE and wavelet-based techniques for the digital restoration of missing parts in paintings. This is part of an ongoing project on the virtual restoration of the 3,600 years old wall paintings excavated in the pre-historic Aegean settlement in Akrotiri, Thera, Greece. [Read more...] [Project page...]

Audio-Visual Speech Recognition

Audiovisual speech recognition refers to the problem of recognizing speech by lipreading. We have developed highly adaptive multimodal fusion rules based on uncertainty compensation which are compatible with synchronous and asynchronous multimodal interaction architectures. Further, our work on AAM-based face representations leads to highly informative visual speech features which can be extracted in real-time. [Read more...] [Software...]

Multigrid Geometric Active Contours

We investigate multigrid techniques for the solution of the time-dependent PDEs of geometric active contour models in Computer Vision. The method allows interactive solution of models whose numerical implementation with conventional techniques has been prohibitively slow. [Read more...] [Software...]

Audio-Visual Speech Inversion

We focus on recovering aspects of vocal tract’s geometry and dynamics from speech, a problem referred to as speech inversion. In our inversion scheme ambiguities inherent to audio-only inversion are resolved by also exploiting visual information from the speaker’s face. [Read more...] [Software...]

Automatic Scale Selection in Nonlinear Scale-Spaces

We consider optimal scale selection for fully automatic image denoising in nonlinear diffusion or morphological scale-spaces. The problem is studied from a statistical model selection viewpoint and we employ cross-validation statistical techniques to address it in a principled way.

Journal Publications

• S. Lefkimmiatis, P. Maragos, and G. Papandreou,
  Bayesian Inference on Multiscale Models for Poisson Intensity Estimation: Applications to Photon-Limited Image Denoising,
  IEEE Transactions on Image Processing, vol. 18, no. 8, pp. 1724-1741, Aug. 2009.
  [pdf] [bib]
• G. Papandreou, A. Katsamanis, V. Pitsikalis, and P. Maragos,
  Adaptive Multimodal Fusion by Uncertainty Compensation with Application to Audio-Visual Speech Recognition,
  IEEE Transactions on Audio, Speech and Language Processing, vol. 17, no. 3, pp. 423-435, Mar. 2009.
  [pdf] [bib] [Read more...]
• A. Katsamanis, G. Papandreou, and P. Maragos,
  Face Active Appearance Modeling and Speech Acoustic Information to Recover Articulation,
  IEEE Transactions on Audio, Speech and Language Processing, vol. 17, no. 3, pp. 411-422, Mar. 2009.
  [pdf] [bib] [Read more...]
• G. Papandreou and P. Maragos,
  Multigrid Geometric Active Contour Models,
  IEEE Transactions on Image Processing, vol. 16, no. 1, pp. 229-240, Jan. 2007.
  [pdf] [bib] [software] [Read more...]

Conference Publications

• S. Lefkimmiatis, G. Papandreou and P. Maragos,
  Poisson-Haar Transform: A Nonlinear Multiscale Representation for Photon-Limited Image Denoising,
  Proc. IEEE Int'l Conf. on Image Processing (ICIP-09), Cairo, Egypt, Nov. 7-11, 2009.
  [pdf] [bib]
• S. Lefkimmiatis, G. Papandreou and P. Maragos,
  Photon-Limited Image Denoising by Inference on Multiscale Models,
  Proc. IEEE Int'l Conf. on Image Processing (ICIP-08), San Diego, CA, U.S.A., Oct. 12-15, 2008.
  [pdf] [bib]
• A. Katsamanis, G. Ananthakrishnan, G. Papandreou, P. Maragos, O. Engwall,
  Audiovisual Speech Inversion by Switching Dynamical Modeling Governed by a Hidden Markov Process,
  Proc. 16th European Signal Processing Conference (EUSIPCO-08), Lausanne, Switzerland, Aug. 2008.
  [pdf] [bib]
• G. Papandreou and P. Maragos,
  Adaptive and Constrained Algorithms for Inverse Compositional Active Appearance Model Fitting,
  Proc. IEEE Int'l Conf. on Computer Vision and Pattern Recognition (CVPR-08), Anchorage, AK, June 2008.
  [pdf] [appendix] [poster] [bib] [software]
• G. Papandreou, P. Maragos, and A. Kokaram,
  Image Inpainting with a Wavelet Domain Hidden Markov Tree Model,
  Proc. IEEE Int'l Conference on Acoustics, Speech, and Signal Processing (ICASSP-08), pp. 773-776, Las Vegas, NV, U.S.A., Mar.-Apr. 2008.
  [pdf] [bib]
• A. Katsamanis, G. Papandreou, and P. Maragos,
  Audiovisual-to-Articulatory Speech Inversion Using Active Appearance Models for the Face and Hidden Markov Models for the Dynamics,
  Proc. IEEE Int'l Conference on Acoustics, Speech, and Signal Processing (ICASSP-08), pp. 2237-2240, Las Vegas, NV, U.S.A., Mar.-Apr. 2008.
  [pdf] [bib]
• G. Papandreou, A. Katsamanis, V. Pitsikalis, and P. Maragos,
  Multimodal Fusion and Learning with Uncertain Features Applied to Audiovisual Speech Recognition,
  Proc. IEEE Workshop on Multimedia Signal Processing (MMSP-07), pp. 264-267, Chania, Greece, October 1-3, 2007.
  [pdf] [bib]
• A. Katsamanis, G. Papandreou, and P. Maragos,
  Audiovisual-to-Articulatory Inversion Using Hidden Markov Models,
  Proc. IEEE Workshop on Multimedia Signal Processing (MMSP-07), pp. 457-460, Chania, Greece, October 1-3, 2007.
  [pdf] [bib]
• V. Pitsikalis, A. Katsamanis, G. Papandreou, and P. Maragos,
  Adaptive Multimodal Fusion by Uncertainty Compensation,
  Proc. Int'l Conference on Spoken Language Processing (ICSLP-06), pp. 2458-2461, Pittsburgh PA, USA, Sep. 17-21, 2006.
  [pdf] [bib]
• A. Katsamanis, G. Papandreou, V. Pitsikalis, and P. Maragos,
  Multimodal Fusion by Adaptive Compensation for Feature Uncertainty with Application to Audiovisual Speech Recognition,
  Proc. 14th European Signal Processing Conference (EUSIPCO-06), Florence, Italy, Sept. 4-8 2006.
  [pdf] [bib]
• G. Papandreou and P. Maragos,
  Image Denoising in Nonlinear Scale-Spaces: Automatic Scale Selection Via Cross-Validation,
  Proc. Int'l Conf. on Image Processing (ICIP-05), Genova, Italy, September 2005.
  [pdf] [bib]
• G. Papandreou and P. Maragos,
  A Cross-Validatory Statistical Approach to Scale Selection for Image Denoising by Nonlinear Diffusion,
  Proc. IEEE Int'l Conf. on Computer Vision and Pattern Recognition (CVPR-05), San Diego, CA, June 2005.
  [pdf] [bib]
• G. Papandreou and P. Maragos,
  A Fast Multigrid Implicit Algorithm for the Evolution of Geodesic Active Contours,
  Proc. IEEE Int'l Conf. on Computer Vision and Pattern Recognition (CVPR-04), Washington DC, June 2004.
  [pdf] [bib] [software] [Read more...]

Book Chapters

• G. Papandreou, A. Katsamanis, V. Pitsikalis and P. Maragos,
  Adaptive Multimodal Fusion by Uncertainty Compensation with Application to Audio-Visual Speech Recognition,
  in Multimodal Processing and Interaction: Audio, Video, Text, edited by P. Maragos, A. Potamianos, and P. Gros, chapter 4, pp. 111-126, Springer-Verlag, New York, 2008.
  [chapter doi] [book doi] [springer] [amazon.com]
• P. Maragos, P. Gros, A. Katsamanis and G. Papandreou,
  Cross-Modal Integration for Performance Improving in Multimedia: A Review,
  in Multimodal Processing and Interaction: Audio, Video, Text, edited by P. Maragos, A. Potamianos, and P. Gros, chapter 1, pp. 3-48, Springer-Verlag, New York, 2008.
  [chapter doi] [book doi] [springer] [amazon.com]

Theses

• G. Papandreou,
  Image Analysis and Computer Vision: Theory and Applications in the Restoration of Ancient Wall Paintings,(in greek)
  ECE School PhD Thesis, 2009. Thesis supervisor: Prof. P. Maragos.
  [pdf] [defense slides] [bib]
• G. Papandreou,
  Fast Algorithms for the Evolution of Geodesic Active Contours with Applications in Computer Vision,(in greek)
  ECE School Diploma Thesis, 2003. Thesis supervisor: Prof. P. Maragos.
  [ps.gz] [bib]

Software

• GAC++: A toolbox for geometric active contours and other related PDE-based computer vision models. See here.
• AAMtools: A toolbox for building Active Appearance Models and fitting them to still and moving images. See here.