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1.
IEEE Trans Pattern Anal Mach Intell ; 29(7): 1285-90, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17496386

ABSTRACT

In this paper, a novel local surface descriptor is proposed and applied to the problem of aligning partial views of a 3D object. The descriptor is based on taking "snapshots" of the surface over each point using a virtual camera oriented perpendicularly to the surface. This representation has the advantage of imposing minimal loss of information be robust to self-occlusions and also be very efficient to compute. Then, we describe an efficient search technique to deal with the rotation ambiguity of our representation and experimentally demonstrate the benefits of our approaches which are pronounced especially when we align views with small overlap.


Subject(s)
Algorithms , Face/anatomy & histology , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Pattern Recognition, Automated/methods , Subtraction Technique , Artificial Intelligence , Biometry/methods , Humans , Reproducibility of Results , Sensitivity and Specificity
2.
Comput Biol Med ; 37(9): 1292-302, 2007 Sep.
Article in English | MEDLINE | ID: mdl-17291482

ABSTRACT

The detection of lumen and media-adventitia borders in intravascular ultrasound (IVUS) images constitutes a necessary step for the quantitative assessment of atherosclerotic lesions. To date, most of the segmentation methods reported are either manual, or semi-automated, requiring user interaction at some extent, which increases the analysis time and detection errors. In this work, a fully automated approach for lumen and media-adventitia border detection is presented based on an active contour model, the initialization of which is performed via an analysis mechanism that takes advantage of the inherent morphologic characteristics of IVUS images. The in vivo validation of the proposed model in human coronary arteries revealed that it is a feasible approach, enabling accurate and rapid segmentation of multiple IVUS images.


Subject(s)
Coronary Artery Disease/diagnosis , Coronary Vessels/diagnostic imaging , Imaging, Three-Dimensional/methods , Ultrasonography/methods , Algorithms , Coronary Artery Disease/diagnostic imaging , Humans , Linear Models , Observer Variation , Reproducibility of Results , Sensitivity and Specificity
3.
IEEE Trans Image Process ; 15(8): 2113-9, 2006 Aug.
Article in English | MEDLINE | ID: mdl-16900669

ABSTRACT

We propose a novel scheme for error-resilient image transmission. The proposed scheme employs a product coder consisting of low-density parity check (LDPC) codes and Reed-Solomon codes in order to deal effectively with bit errors. The efficiency of the proposed scheme is based on the exploitation of determinate symbols in Tanner graph decoding of LDPC codes and a novel product code optimization technique based on error estimation. Experimental evaluation demonstrates the superiority of the proposed system in comparison to recent state-of-the-art techniques for image transmission.


Subject(s)
Artifacts , Computer Communication Networks , Data Compression/methods , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Signal Processing, Computer-Assisted , Algorithms , Quality Control , Reproducibility of Results , Sensitivity and Specificity
4.
IEEE Trans Image Process ; 15(1): 54-67, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16435536

ABSTRACT

The transmission of JPEG2000 images over wireless channels is examined using reorganization of the compressed images into error-resilient, product-coded streams. The product-code consists of Turbo-codes and Reed-Solomon codes which are optimized using an iterative process. The generation of the stream to be transmitted is performed directly using compressed JPEG2000 streams. The resulting scheme is tested for the transmission of compressed JPEG2000 images over wireless channels and is shown to outperform other algorithms which were recently proposed for the wireless transmission of images.


Subject(s)
Algorithms , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Information Storage and Retrieval/methods , Signal Processing, Computer-Assisted , Telecommunications , Video Recording/methods , Computer Communication Networks , Computer Graphics , Numerical Analysis, Computer-Assisted
5.
IEEE Trans Image Process ; 14(11): 1890-901, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16279187

ABSTRACT

A novel image transmission scheme is proposed for the communication of set partitioning in hierarchical trees image streams over wireless channels. The proposed scheme employs turbo codes and Reed-Solomon codes in order to deal effectively with burst errors. An algorithm for the optimal unequal error protection of the compressed bitstream is also proposed and applied in conjunction with an inherently more efficient technique for product code decoding. The resulting scheme is tested for the transmission of images over wireless channels. Experimental evaluation clearly demonstrates the superiority of the proposed transmission system in comparison to well-known robust coding schemes.


Subject(s)
Algorithms , Computer Communication Networks , Data Compression/methods , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Signal Processing, Computer-Assisted , Telecommunications
6.
IEEE Trans Image Process ; 14(2): 152-68, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15700521

ABSTRACT

This paper presents a complete face authentication system integrating both two-dimensional (color or intensity) and three-dimensional (3-D) range data, based on a low-cost 3-D sensor, capable of real-time acquisition of 3-D and color images. Novel algorithms are proposed that exploit depth information to achieve robust face detection and localization under conditions of background clutter, occlusion, face pose alteration, and harsh illumination. The well-known embedded hidden Markov model technique for face authentication is applied to depth maps and color images. To cope with pose and illumination variations, the enrichment of face databases with synthetically generated views is proposed. The performance of the proposed authentication scheme is tested thoroughly on two distinct face databases of significant size. Experimental results demonstrate significant gains resulting from the combined use of depth and color or intensity information.


Subject(s)
Algorithms , Artificial Intelligence , Color , Face/anatomy & histology , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Pattern Recognition, Automated/methods , Photogrammetry/methods , Cluster Analysis , Humans , Image Enhancement/methods , Information Storage and Retrieval/methods , Numerical Analysis, Computer-Assisted , Patient Identification Systems/methods , Reproducibility of Results , Security Measures , Sensitivity and Specificity , Signal Processing, Computer-Assisted , Subtraction Technique
7.
IEEE Trans Image Process ; 13(12): 1604-17, 2004 Dec.
Article in English | MEDLINE | ID: mdl-15575155

ABSTRACT

The issue of copyright protection of digital multimedia data has attracted a lot of attention during the last decade. An efficient copyright protection method that has been gaining popularity is watermarking, i.e., the embedding of a signature in a digital document that can be detected only by its rightful owner. Watermarks are usually blindly detected using correlating structures, which would be optimal in the case of Gaussian data. However, in the case of DCT-domain image watermarking, the data is more heavy-tailed and the correlator is clearly suboptimal. Nonlinear receivers have been shown to be particularly well suited for the detection of weak signals in heavy-tailed noise, as they are locally optimal. This motivates the use of the Gaussian-tailed zero-memory nonlinearity, as well as the locally optimal Cauchy nonlinearity for the detection of watermarks in DCT transformed images. We analyze the performance of these schemes theoretically and compare it to that of the traditionally used Gaussian correlator, but also to the recently proposed generalized Gaussian detector, which outperforms the correlator. The theoretical analysis and the actual performance of these systems is assessed through experiments, which verify the theoretical analysis and also justify the use of nonlinear structures for watermark detection. The performance of the correlator and the nonlinear detectors in the presence of quantization is also analyzed, using results from dither theory, and also verified experimentally.


Subject(s)
Algorithms , Computer Graphics , Image Interpretation, Computer-Assisted/methods , Information Storage and Retrieval/methods , Nonlinear Dynamics , Patents as Topic , Pattern Recognition, Automated/methods , Computer Security , Hypermedia , Models, Statistical , Product Labeling/methods , Reproducibility of Results , Sensitivity and Specificity , Signal Processing, Computer-Assisted
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