Computational Imaging / Transform and Spectral Techniques Group

The Computational Imaging group is part of the Department of Signal Processing at Tampere University of Technology. The group is specialized in forefront research on various applied and fundamental aspects of imaging, with particular emphasis on the computational methods that make advanced digital imaging applications possible.

Prof. Karen Egiazarian (group leader)
Prof. Vladimir Katkovnik
Dr. Atanas Gotchev
Dr. Alessandro Foi

11 PhD students, 10 MSc students complete list of group members

The group has long-standing national and international collaborations with industry and academia.

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APPLIED RESEARCH

Imaging

• noise modeling and analysis for digital imaging sensors
• clipped Poissonian-Gaussian modelling for raw data
• automatic noise estimation algorithms for single or multiple images
• image and video filtering: denoising, deblurring, deblocking, sharpening, enhancement
• block-matching 3D filtering (BM3D) algorithms
• shape-adaptive DCT algorithms
• filtering for data corrupted by signal-dependent noise
• denoising of photon-limited Poisson data
• multiframe blind deconvolution
• filtering framework for over- and underexposed (clipped) noisy data
• color filter array interpolation (demosaicking)
• anisotropic color interpolation algorithms for noisy raw Bayer data
• joint denoising-interpolation-deblurring of noisy raw Bayer data
• image/video upsampling and super-resolution
• nonlinear high-quality upsampling and super-resolution based recursive spatially adaptive block-matching filtering
• high dynamic range imaging
• efficient composition and tone-mapping techniques in luminance-chrominance color space for high-quality HDR imaging (noise and misalignment resilient)

Tomographic reconstruction and compressive sensing

• image reconstruction from highly incomplete data

Compression

• compression of raw Bayer pattern data
• optimal lossy compression of noisy images
• AGU

3D Visual Communications and Video Processing for Mobile Devices

• MDC for images, video, stereo-video and 3D geometry
• Optimized visualizations on auto-stereoscopic displays
• measurement of artifacts on various 3D displays
• semi-active 3D auto-stereoscopic displays
• mobile 3D auto-stereoscopic displays
• anti-aliasing filtering for 3D displays
• Mobile 3DTV content delivery optimization over DVB-H system
• error-resilient transmission of 3D video over DVB-H
• pre- and post-processing of 3D video
• stereoscopic artifacts on mobile 3D auto-stereoscopic displays
• visual quality enhancement and objective assesment of 3D video

Digital Holography

• Reconstruction of wavefield distributions
• Phase local approximation

Transforms methods for electroencephalography (EEG)

• Automatic removal of muscle and eye artifacts from scalp EEG measurements
• Blind estimation of cerebral EEG sources
• Measuring functional and effective connectivity between EEG sources
• Understanding the role of brain connectivity in neurodegeneration

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FUNDAMENTAL RESEARCH

Statistical methods

• automatic scale/bandwidth selection in nonparametric regression
• local polynomial approximation (LPA) and the intersection of confidence intervals (ICI) technique
• anisotropic estimation
• anisotropic adaptation based on multidirectional polynomial fit with varying scale
• shape-adaptive overcomplete transforms
• nonlocal transform-based filtering
• grouping and collaborative filtering
• collaborative ell-0 norm prior
• fast transforms
• nonlinear transformations
• optimization of variance-stabilizing transformations
• optimal inversion of variance-stabilizing transformations
• interaction between censoring and heteroskedasticity

Sampling and interpolation

• design of optimized piecewise-polynomial resampling kernels
• effient filter structures for decimation and interpolation
• non-uniform image resampling
• non-uniform sampling of the diffraction field

Image perception

• perceptual image quality
• eye tracking and gaze analysis
• 3D video quality of experience

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KEY PUBLICATIONS

Gomez-Herrero, G., Rutanen, K., and Egiazarian, K., “Blind source separation by entropy rate minimization”, preprint (August 2009), to appear IEEE Sig. Proc. Lett..

Cantero, J. L., Atienza, M., Gomez-Herrero, G., Cruz-Vadell, A., Gil-Neciga, E., Rodriguez-Romero, R. and Garcia-Solis, D., “Functional integrity of thalamocortical circuits differentiates normal aging from mild cognitive impairment”, preprint (May 2009), to appear Human Brain Mapping. doi:10.1002/hbm.20819

Katkovnik, V., A. Foi, K. Egiazarian, and J. Astola, “From local kernel to nonlocal multiple-model image denoising”, preprint (July 2009), to appear Int. J. Computer Vision. doi:10.1007/s11263-009-0272-7

Foi, A., “Clipped noisy images: heteroskedastic modeling and practical denoising”, Signal Processing, vol. 89, no. 12, pp. 2609-2629, December 2009. doi:10.1016/j.sigpro.2009.04.035

Gomez-Herrero, G., Atienza, M., Egiazarian, K. and Cantero, J. L., “Measuring directional coupling between EEG sources”, Neuroimage, vol. 43, no. 3, pp. 497-508, November 2008.doi:10.1016/j.neuroimage.2008.07.032

Foi, A., M. Trimeche, V. Katkovnik, and K. Egiazarian, “Practical Poissonian-Gaussian noise modeling and fitting for single image raw-data”, IEEE Trans. Image Process., vol. 17, no. 10, pp. 1737-1754, October 2008.

Katkovnik, V., J. Astola, and K. Egiazarian, “Discrete diffraction transform for propagation, reconstruction, and design of wavefield distributions”, Applied Optics, vol. 47, no. 19, pp. 3481-3493, July 2008.

Katkovnik, V., J. Astola, and K. Egiazarian, “Phase local approximation (PhaseLa) technique for phase unwrap from noisy data”, IEEE Trans. Image Process., vol. 17, no. 6, pp. 833-846, June 2008.

Katkovnik, V., and V. Spokoiny, “Spatially Adaptive Estimation via Fitted Local Likelihood Techniques”, IEEE Trans. Image Process., vol. 56, no. 3, pp. 873-886, March 2008.

Tichavsky, P., Koldovsky, Z., Yeredor, A., Gomez-Herrero, G., and Doron, E., “A hybrid technique for blind separation of non-Gaussian and time-correlated sources using a multicomponent approach”, IEEE Trans. Neural Networks, vol. 19, no. 3, pp. 421-430, March 2008.

Foi, A., S. Alenius, V. Katkovnik, and K. Egiazarian, “Noise measurement for raw-data of digital imaging sensors by automatic segmentation of non-uniform targets”, IEEE Sensors Journal, vol. 7, no. 10, pp. 1456-1461, October 2007.

Pirinen, O., A. Foi, and A. Gotchev, “Color High Dynamic Range Imaging: The Luminance-Chrominance Approach”, Int. J. Imaging Systems and Technology (IJIST), Special Issue on Applied Color Image Processing, vol. 17., no. 3, pp. 152-162, October 2007.

Dabov, K., A. Foi, V. Katkovnik, and K. Egiazarian, “Image denoising by sparse 3D transform-domain collaborative filtering, ” IEEE Trans. Image Process., vol. 16, no. 8, pp. 2080-2095, August 2007.

Foi, A., V. Katkovnik, and K. Egiazarian, “Pointwise Shape-Adaptive DCT for High-Quality Denoising and Deblocking of Grayscale and Color Images”, IEEE Trans. Image Process., vol. 16, no. 5, pp. 1395-1411, May 2007.

Paliy, D., V. Katkovnik, R. Bilcu, S. Alenius, K. Egiazarian, “Spatially Adaptive Color Filter Array Interpolation for Noiseless and Noisy Data”, International Journal of Imaging Systems and Technology (IJISP), Special Issue on Applied Color Image Processing, vol. 17, iss. 3, pp. 105-122, October 2007.

Katkovnik, V., K. Egiazarian, and J. Astola, Local Approximation Techniques in Signal and Image Processing, SPIE Press, Monograph Vol. PM157, September 2006.

Katkovnik, V., K. Egiazarian, and J. Astola, “A Spatially Adaptive Nonparametric Regression Image Deblurring”, IEEE Trans. Image Process., vol. 14, no. 10, pp. 1469-1478, October 2005.

Katkovnik, V., “Multiresolution local polynomial regression: a new approach to pointwise spatial adaptation”, Digital Signal Process., vol. 15, pp. 73-116, 2005.

Katkovnik, V., K. Egiazarian, and J. Astola, “Adaptive window size image de-noising based on intersection of confidence intervals (ICI) rule”, J. of Math. Imaging and Vision, vol. 16, no. 3, pp. 223-235, 2002.

Nikolaev, N., A. Gotchev, K. Egiazarian, and Z. Nikolov, “Suppression of electromyogram interference on the electrocardiogram by transform domain denoising”, Medical & Biological Engineering and Computing, vol. 39, pp. 649-655, 2001.

Katkovnik, V., “A new method for varying adaptive bandwidth selection”, IEEE Trans. on Signal Proc., vol. 47, no. 9, pp. 2567-2571, 1999.

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Full list of publictions