Xiaolin Wu

Professor

NSERC Senior Industrial Research Chair

Associated Editor, IEEE Trans. on Image Processing

IEEE Fellow

Department of Electrical & Computer Engineering
ITB A315
McMaster University
Hamilton, Ontario, Canada, L8G 4K1

phone: 905 525-9140 ext 24190

fax: 905 521-2922

email: xwu at ece.mcmaster.ca

COURSES: Data Structures and Algorithms (2SI4) ; Image Processing (4TN4); Numerical Analysis (3SK3)

RESEARCH:

My general research activities are in visual/multimedia computing and communications. I have published numerous algorithms for computer graphics and image processing (image coding in particular), some of which are being used by practitioners, such as a fast optimal color quantizer, and a Context-based Adaptive Lossless Image Codec (CALIC) which was developed jointly with Nasir Memon as a candidate algorithm for the new JPEG lossless standard. CALIC(executable) is widely used as a benchmark in performance evaluation of lossless image codecs.

My recent breakthrough in information display technology (patents pending)

(featured in MIT Technology Review http://m.technologyreview.com/blog/arxiv/27490/)

Temporal Psychovisual Modulation (TPVM)

Via an ingenious interplay of critical flicker frequency of human vision, high refresh-rate digital display and optoelectronic viewing devices, TPVM is a new display paradigm that differs fundamentally, in design principle, user experience and cost effectiveness, from MIT’s head-mounted display (HMD) technology and from Sony’s recent screen sharing technology, while offering more and exciting functionalities.

visor7a

The scientific principle of TPVM: atom frames emitted by high-speed display are weighted by active LC glasses and perceived by the human visual system (HSV) as an image. TPVM allows concurrent multiple self-intended exhibitions via a common display medium, an optoelectronic-psychovisual process modeled by non-negative matrix factorization. Different images are perceived by different viewers whose LC glasses modulate the same sequence of atom frames differently (see below).

visor7b See how TPVM works

In virtual reality (VR) and augmented reality (AR), TPVM allows

many users interact with the same virtual world and at the same time enjoy each other’s physical presence (e.g., surfing together), which is impossible with HMD.
a bulk of imaging computations off-loaded from HMD (electronic) to HSV (biologic), making user-worn viewing apparatus much simpler, lighter and far less expensive.

Examples in 3D medical visualization; Examples in security/privacy protection.

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I and my students have also developed

· A highly competitive color demosaicking technique: Primary-Consistent Soft-Decision (PCSD executable: pcsd.rar) color demosaicking algorithm.

· A highly competitive image interpolation technique: Soft-decision Adaptive Interpolation (SAI executable: sai.rar) algorithm.

· MARX algorithm (Model-based Adaptive Recovery of Compressive Sensing): (executable: marx.rar).

Our new book: Network-aware Source Coding and Communication, Cambridge University Press, 2011 new book

Selected Publications:

Network-aware source coding and communication

X. Wu, B. Ma and N. Sarshar, “Rainbow network problems and multiple description coding”, IEEE Trans. on Information Theory, vol. 54, no. 10, pp. 4565-4574, Oct. 2008.
X. Wu, X. Wang, and Z. Wang, "Resource-scalable joint source-channel MAP and MMSE estimation of multiple descriptions", IEEE Trans. on Signal Processing, vol. 57, no. 1, pp. 279-288, Jan. 2009.
J. Wang, J. Chen, and X. Wu, “On the sum rate of Gaussian multiterminal source coding: new proofs and results”, IEEE Trans. on Information Theory, vol. 56, no. 8, pp. 3946-3960, Aug. 2010.
X. Wang and X. Wu, "Index assignment optimization for joint source-channel MAP decoding", IEEE Trans. on Communications, vol. 58, no. 3, pp. 901-910, Mar 2010.
X. Wu, X. Wang, and Z. Wang, "Resource-scalable joint source-channel MAP and MMSE estimation of multiple descriptions", IEEE Trans. on Signal Processing, vol. 57, no. 1, pp. 279-288, Jan. 2009.
S. Dumitrescu and X. Wu, “On the complexity of joint source-channel decoding of Markov sequences over memoryless channels”, IEEE Trans. on Communications, vol. 56, no. 6, pp. 877-885, June 2008.
S. Dumitrescu, X. Wu, and Z. Wang, “Efficient algorithms for optimal uneven protection of single and multiple scalable code streams against packet erasures”, IEEE Trans. on Multimedia, vol. 9, no. 7, pp. 1466-1474, Nov. 2007.
X. Wu, S. Dumitrescu, and Z. Wang, “Monotonicity-based fast algorithm for MAP estimation of Markov sequences over noisy channels”, IEEE Trans. on Information Theory, vol.50, no.7, pp.1539-1544, July 2004.
Z. Wang and X. Wu, “Length-constrained MAP decoding of variable length encoded Markov sequences”, IEEE Trans. on Communications, vol.54, no.7, pp.1259-1266, July, 2006.
S. Dumitrescu, X. Wu, and Z. Wang, ”Globally optimal uneven error protected packetization of scalable code streams”, IEEE Trans. on Multimedia, vol. 6, no. 2, pp. 230-239, Apr. 2004.
N. Sarshar and X. Wu, “A practical approach to joint network-source coding”, Proc. of DCC 2006 (dcc06.pdf).
X. Huang and X. Wu, “Optimal index assignment for multiple description lattice vector quantization”, Proc. of DCC 2006 (IAMDLVQ.pdf).
X. Wu, X. Wang, and J. Wang, “Joint source-channel decoding of multiple description quantized Markov sequences”, Proc. of DCC 2006 (MDQMAP.pdf).
B. Ma and X. Wu, “Maximum network flow of multiple description codes”, Proc. of NetCod 2005, Apr. 2005.
N. Sarshar and X. Wu, “Statistical mechanics of optimal networked source coding”, Proc. of NetCod 2005, Apr. 2005.
X. Wu, S. Cheng and Z. Xiong, ``On packetization of embedded multimedia bitstreams'', IEEE Trans. on Multimedia, 2001, vol. 3, pp. 132-140, 2001.

Image Coding

X. Wu, G. Zhai, X. Yang and W. Zhang, “Adaptive sequential prediction of multidimensional signals with applications to lossless image coding”, IEEE Trans. on Image Processing, vol. 20, no. 1, pp. 36-42, Jan. 2011.
X. Wu, X. Zhang, and X. Wang, "Low bit-rate image compression via adaptive down-sampling and constrained least squares upconversion", IEEE Trans. on Image Processing, vol. 18, no. 3, pp. 552-561, Mar. 2009.
X. Wu, S. Dumitrescu, and N. Zhang, "On multirate optimality of JPEG 2000 code streams", IEEE Trans. on Image Processing, vol. 14, no. 12, pp. 2012-2023, Dec. 2005.
N. Sarshar and X. Wu, “On rate-distortion models for natural images”, IEEE Trans. on Image Processing, vol. 16, no. 5, pp. 1383-1394, May 2007.
N. Zhang and X. Wu, “Lossless compression of color mosaic images”, IEEE Trans. on Image Processing, vol. 15, no. 6, pp. 1379-1388, June 2006.
W. Ding, F. Wu, X. Wu, and S. Li, “Adaptive directional lifting-based wavelet transform for image coding ”, IEEE Trans. on Image Processing, vol. 16, no. 2, Feb. 2007.
X. Xue and X. Wu, “Directly operable image representation of multiscale primal sketch”, IEEE Trans. on Multimedia, vol. 7, no. 5, pp. 805-816, Oct. 2005

S. Cheng, Z. Xiong, and X. Wu, ``Fast trellis coded color quantization of images'', Real-Time Imaging, vol. 8, pp. 265-275, August 2002.
X. Wu and N. Memon, "Lossless interframe image compression via context modeling", IEEE Trans. on Image Processing, vol. 9, no. 5, pp. 994-1001, May 2000.
X. Wu and P. Bao, "-constrained high-fidelity image compression via adaptive context modeling", IEEE Trans. on Image Processing, vol. 9, no. 4, pp. 536-542, April 2000.
X. Wu, J. Wen, and W-H Wong, "Conditional entropy coding of VQ indexes for image compression", IEEE Trans. on Image Processing, vol. 8, no. 8, pp. 1005-1013, Aug. 1999.
Z. Xiong and X. Wu, "Wavelet image coding using trellis coded space-frequency quantization", IEEE Signal Processing Letters, pp. 158-161, July 1999.
P. Bao and X. Wu, ``-constrained near-lossless image compression using weighted finite automata encoding'', Computers and Graphics, vol. 22, no. 2, pp. 217-223, June 1998.
X. Wu, "Lossless compression of continuous-tone images via context selection, quantization, and modeling'', IEEE Trans. on Image Processing, vol. 6, no. 5, pp. 656-664, May 1997.
X. Wu and N. Memon, ``Context-based, adaptive, lossless image codec'', IEEE Trans. on Communications, vol. 45, no. 4, pp. 437-444, April 1997.
N. Memon and X. Wu, ``Recent developments in context-based predictive techniques for lossless image compression'', The Computer Journal, vol. 40, no. 2/3, pp. 127-136, 1997.
X. Wu and Y. Fang, "A segmentation-based predictive multiresolution image coder", IEEE Trans. on Image Processing, vol. 4, no. 1, pp. 34-47, 1995.
X. Wu, "Image coding by adaptive tree-structured segmentation", IEEE Trans. on Information Theory, vol. 38, no. 6, pp. 1755-1767, Nov. 1992.

Image and Signal Processing

X. Wu, “A linear programming approach for optimal contrast-tone mapping", IEEE Trans. Image Processing, (to appear).
G. Zhai, X. Wu, X. Yang and W. Lin, “A psychovisual quality metric in free energy principle”, IEEE Trans. Image Processing, (accepted).
X. Wu and X. Zhang, “Joint color decrosstalk and demosaicking for CFA cameras”, IEEE Trans. Image Processing, vol. 19, no. 12, pp. 3181-3189, Dec. 2010.
X. Zhang, X. Wu, “Image interpolation by adaptive 2D autoregressive modeling and soft-decision estimation”, IEEE Trans. on Image Processing, vol. 17, no. 6, pp. 887-896, June 2008.
F. Zhang, X. Wu, X. Yang, W. Zhang, "Robust color demosaicking with adaptation to varying spectral correlations", IEEE Trans. on Image Processing, vol. 18, no. 12, pp. 2706-2717, Dec. 2009.
L. Zhang, X. Wu and D. Zhang, “Color reproduction from noisy CFA data of single sensor digital cameras”, IEEE Trans. on Image Processing, vol. 16, no. 9, pp. 2184-2197, Sept. 2007.
X. Wu and L. Zhang, “Color video demosaicking via motion estimation and data fusion”, IEEE Trans. on Circuit and Syst. for Video Tech., vol. 16, no.2, pp. 231-240, Feb. 2006.
X. Wu and L. Zhang, “Improvement of color video demosaicking in temporal domain,” IEEE Trans. Image Processing, vol.15, no.10, Oct. 2006.
L. Zhang and X. Wu, “Image interpolation via directional filtering and data fusion,” IEEE Trans. Image Processing, vol.15, no.8, pp. 2226-2238, Aug. 2006.
X. Wu and N. Zhang, “Primary-consistent soft-decision color demosaicking for digital cameras", IEEE Trans. on Image Processing, vol. 13, no. 9, pp. 1263-1274, Sept. 2004.
L. Zhang and X. Wu, "Color demosaicking via directional linear minimum mean square-error estimation", IEEE Trans. on Image Processing, vol. 14, no. 12, pp. 2167-2178, Dec. 2005.
P. Bao, L. Zhang and X. Wu, “Canny edge detection enhancement by scale multiplication,” IEEE Trans. Pattern Analysis and Machine Intelligence, vol. 27, no. 9, pp. 1485-1490, Sept. 2005.
L. Zhang, P. Bao, and X.Wu, “Multiscale-LMMSE-based image denoising with optimal wavelet selection”, IEEE Trans. on Circuit and Syst. for Video Tech., vol. 15, no. 4, pp. 496-481, Apr. 2005.
L. Zhang, X. Wu, Q. Pan and H. Zhang, "Multiresolution modeling and estimation of multisensor data", IEEE Trans. on Signal Processing, pp. 3170-3182, Nov. 2004.
L. Zhang, P. Bao, and X. Wu, "Wavelet-based estimation of fractional Brownian motion embedded in noisy environment", IEEE Trans. on Information Theory, vol. 50, no. 9, pp. 2194-2200, Sept. 2004.
L. Zhang, X. Wu, and P. Bao, "Noisy signal compression by wavelet transform with optimal downsampling", International Journal of Wavelets, Multiresolution and Information Processing, vol. 1, no. 4, pp. 407-423, Dec. 2003.
L. Zhang, P. Bao, and X.Wu, ”Hybrid inter- and intra-wavelet scale image restoration”, Pattern Recognition, p. 1737-1746, vol. 36 (8), Aug. 2003.

Signal quantization and source coding

N. Sarshar and X. Wu, “On L∞ properties of multiresolution scalar quantizers”, IEEE Trans. on Information Theory, vol. 56, no. 11, pp. 5805-5810, Nov. 2010.
S. Dumitrescu and X. Wu, "On properties of locally optimal multiple description scalar quantizers with convex cells", IEEE Trans. on Information Theory, vol. 55, no. 12, pp. 5591-5606, Dec. 2009.
S. Dumitrescu and X. Wu, “Lagrangian optimization of two-description scalar quantizers”, IEEE Trans. on Information Theory, vol. 53, no. 11, pp. 3990-4012, Nov. 2007.
M. Xue, X. Wu, P. Franti, “Context quantization by kernel Fisher discriminant”, IEEE Trans. on Image Processing, vol. 15, no. 1, pp. 169-177, Jan. 2006.
S. Dumitrescu and X. Wu, “Optimal two-description scalar quantizer design”, Algorithmica, vol. 41, no. 4, pp. 269-287, Feb. 2005.
S. Dumitrescu and X. Wu, “Algorithms for optimal multi-resolution quantization", Journal of Algorithms, vol. 50, no. 1, pp. 1-22, Jan. 2004.
D. Chen, Y. Chiang, N. Memon, X. Wu, “Alphabet partitioning techniques for semi-adaptive Huffman coding of large alphabets”, IEEE Trans. on Communications, vol. 55, no. 3, March 2007.
S. Forchhammer, X. Wu, and J. D. Andersen, "Optimal context quantization in lossless compression of image data sequences", IEEE Trans. on Image Processing, vol. 13, no. 4, pp. 509-517, Apr. 2004.
X. Wu, ``Optimal binary vector quantization via enumeration of covering codes'', IEEE Trans. on Information Theory, vol. 43, no. 2, pp. 638-645, March 1997.
X. Wu, "YIQ vector quantization in a new color palette architecture", IEEE Trans. on Image Processing, vol. 5. no. 2, pp. 321-329, 1996.
X. Wu and K. Zhang, "Quantizer monotonicities and quantizer design algorithms", IEEE Trans. on Information Theory, vol. 39, no. 3, pp. 1049-1053, May 1993.
X. Wu, "Color quantization by dynamic programming and principal analysis", ACM Trans. on Graphics, vol. 11, no. 4 (TOG special issue on color), pp. 348-372, Oct. 1992.
X. Wu, "On convergence of Lloyd's method I", IEEE Trans. on Information Theory, vol. 38, no. 1, pp. 171-174, Jan. 1992.
X. Wu, "Optimal quantization by matrix-searching," Journal of Algorithms, vol. 12, no. 4, pp. 663-673, Dec. 1991.

Biomedical Imaging

X. Wu and T. Qiu, “Wavelet coding of volumetric medical images for high throughput and operability”, IEEE Trans. on Medical Imaging, vol. 24, no. 6, pp. 719-727, June 2005.
X. Wu, S. Dumitrescu, P. Biyani, and Q. Wu, “Fast chromosome karyotyping by auction algorithm”, Int. J. of Bioinformatics and Applications, vol. 2, no. 3, 2006.
P. Biyani, X. Wu and A. Sinha, “Joint classification and pairing of human chromosomes”, IEEE/ACM Trans. on Computational Biology and Bioinformatics, vol. 2, no. 2, pp. 102-109, Apr. 2005.
Z. Xiong, X. Wu, S. Cheng, and J. Hua, "Lossy-to-lossless compression of medical volumetric data using 3D integer wavelet transforms", IEEE Transactions on Medical Imaging, vol. 22, pp. 459-470, March 2003.

Steganalysis and Watermarking

S. Dumitrescu and X. Wu, “A new framework of LSB steganalysis of digital media”, IEEE Trans. on Signal Processing, vol. 53, no. 10, pp. 3923-3935, Oct., 2005.
S. Dumitrescu, X. Wu, and Z. Wang, "Detection of LSB steganography via sample pair analysis", IEEE Transactions on Signal Processing, pp. 1995-2007, July 2003.
X. Wu, "Semantically transparent fingerprinting for copyright protection of digital cinema", Proc. of 2003 SPIE Conference on Electronic Imaging, Santa Clara, CA., vol. 5020, pp. 574-579, Feb. 2003.