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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Cuadros-Vargas, Alex J. Nonato, Luis Gustave Minghim, Rosane Etiene, Tiago Institute de Ciências Matemáticas e de Computaçã o CP 668 Sao Carlos 13560-970 Sao Paulo Brazil

ISBN: (纸本)0769523897

Generating triangular meshes from images is a task important to many applications. Usually, techniques that can do that either take as starting point a segmented image or generate a mesh without distinguishing different structures contained in the image. In both cases the results can be satisfactory for a number of applications, but the pre-segmentation and the absence of well defined structures imply in difficulties using the resulting mesh for simulations. Furthermore, guarantee of good quality meshes is also a common problem in previous results. In this work we present a new technique for mesh generation that handles these problems well. First, it eliminates the need for preprocessing by building the segmentation into the mesh generation process. Second, the mesh generation process takes into acount the quality of the mesh elements, producing as result meshes of better quality than previous techniques. © 2005 IEEE.

关键词： image quality

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A linear algorithm for exact pattern matching in planar subdivisions

A linear algorithm for exact pattern matching in planar subd...

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： De Andrade Neto, Pedro Ribeiro Guedes, André Luiz Pires Department of Computer Science Federal University of Paraná Centre Politécnico - Jardim das Américas Curitiba-PR 81531-990 Brazil

ISBN: (纸本)0769523897

Graph sub-isomorphism is a very common approach to solving pattern search problems, but this is a NP-complete problem. this way, it is necessary to invest in research of approximate solutions, or in special cases of the problem. Planar subdivisions can be considered as a special case of graphs, because, in addition to nodes and edges, there is a more rigid topology in relation to the order of the edges, arising to the concept of face. this work presents a linear algorithm for pattern search in planar subdivisions. the presented algorithm is based on a hybrid approach between the dual and the region adjacency graph (RAG) to represent the patterns, saving any additional storage cost. thus, the patterns are looked over the search subdivision, using a region growing algorithm. © 2005 IEEE.

关键词： Pattern matching

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Reduction of interband correlation for landsat image compression

Reduction of interband correlation for landsat image compres...

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Acevedo, Daniel G. Ruedin, Ana M. C. Departamento de Computatión Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires

ISBN: (纸本)0769523897

We present a lossless compressor for multispectral images that exploits interband correlations. Each band is divided into blocks, to which a wavelet transform is applied. the wavelet coefficients are predicted by means of a linear combination of coefficients belonging to the same orientation and spatial location. the prediction errors are then encoded with an entropy - based coder. Our original contributions are i) the inclusion, among the candidates for prediction, of coefficients of the same location from other spectral bands, ii) the calculation of weights tuned to the landscape being processed, iii) a fast block classification and a different band-ordering for each landscape. Our compressor reduces the size of an image to about a fourth of its original size. Our method is equivalent to LOCO-I, on 3 of the images tested it was superior. It is superior to other lossless compressors: WinZip, JPEG2000 and PNG. © 2005 IEEE.

关键词： image compression

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A RBFN perceptive model for image thresholding

A RBFN perceptive model for image thresholding

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Lopes, Fabrício Martins Consularo, Luís Augusto CEFET-PR - Centro Federal de Educação Tecnológica do Paraná Av. Alberto Carazzai 1640 86300-000 Cornelio Procopio PR Brazil UNIMEP - Universidade Metodista de Piracicaba Rodovia do Açúcar Km 156 13400-911 Piracicaba SP Brazil

ISBN: (纸本)0769523897

the digital image segmentation challenge has demanded the development of a plethora of methods and approaches. A quite simple approach, the thresholding, has still been intensively applied mainly for real-time vision applications. However, the threshold criteria often depend on entropic or statistical image features. this work searches a relationship between these features and subjective human threshold decisions. then, an image thresholding model based on these subjective decisions and global statistical features was developed by training a Radial Basis Functions Network (RBFN). this work also compares the automatic thresholding methods to the human responses. Furthermore, the RBFN-modeled answers were compared to the automatic thresholding. the results show that entropic-based method was closer to RBFN-modeled thresholding than variance-based method. It was also found that another automatic method which combines global and local criteria presented higher correlation with human responses. © 2005 IEEE.

关键词： image segmentation

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image formation of multifrequency vibro-acoustography: theory and computational simulations

Image formation of multifrequency vibro-acoustography: Theor...

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Silva, Glauber T. Urban, Matthew W. Departamento de Tecnologia da Informação Universidade Federal de Alagoas Maceió AL 57072-970 Brazil Department of Physiology and Biomedical Engineering Mayo Clinic College of Medicine Rochester MN 55905 United States

ISBN: (纸本)0769523897

this paper presents an extension of vibro-acoustography imaging technique. the standard technique relies on the single-frequency dynamic radiation force (or stress) produced by a highly focused dual-frequency ultrasound beam. We propose a multifrequency vibro-acoustography method based on the radiation stress generated by a beam with multiple frequencies. the system point-spread function (PSF) is obtained in terms of the acoustic emission by a point-target in response to the employed radiation stress. the PSF is evaluated for an eight- and a sixteen-element sector array transducers. three phantom images are used to show how the system transforms them into observed data. Considering only visual criteria such as contrast and resolution, simulations show the sixteen-element sector transducer renders better images. © 2005 IEEE.

关键词： Acoustic imaging

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Multi-scale optimization strategy in image registration based navigation system for bronchofiberoscopic procedures

Multi-scale optimization strategy in image registration base...

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14th symposium on New Technologies in Measurement and Instrumentation and 10th Workshop on ADC Modelling and Testing

作者： Turcza, Pawel Department of Instrumentation and Measurement AGH University of Science and Technology Al. Mickiewicza 30 30-059 Kraków Poland

image processing based navigation systems establish the position of bronchofiberoscopy tip by registering images from endoscope camera to images obtained from virtual camera observing virtual objects generated by the computer from CT data. the paper propose application of multi-scale optimization strategy in image registration algorithm in such a navigation system. Proposed strategy intends to enable real-time operation of navigation system by reduction of computational complexity, increase of robustness to local minima and improvement registration process convergence. Some initial verification results are presented.

关键词： Navigation systems

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Single-image shape from defocus

Single-image shape from defocus

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Torreão, José R. A. Fernandes, João L. Instituto de Computação Universidade Federal Fluminense 24210-240 Niterói RJ Brazil

ISBN: (纸本)0769523897

the limited depth of field causes scene points at various distances from a camera to be imaged with different amounts of defocus. If images captured under different aperture settings are available, the defocus measure can be estimated and used for 3D scene reconstruction. Usually, defocusing is modeled by gaussian convolution over local image patches, but the estimation of a defocus measure based on that is hampered by the spurious high-frequencies introduced by windowing. Here we show that this can be ameliorated by the use of unnormalized gaussians, which allow defocus estimation from the zero-frequency Fourier component of the image patches, thus avoiding spurious high frequencies. As our main contribution, we also show that the modified shape from defocus approach can be extended to shape estimation from single shading inputs. this is done by simulating an aperture change, via gaussian convolution, in order to generate the second image required for defocus estimation. As proven here, the gaussian-blurred image carries an explicit depth-dependent blur component - which is missing from an ideal shading input -, and thus allows depth estimation as in the multi-image case. © 2005 IEEE.

关键词： image reconstruction

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Particle filter-based predictive tracking for robust fish counting

Particle filter-based predictive tracking for robust fish co...

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Morais, Erikson F. Campos, Mario F. M. Pádua, Flávio L. C. Carceroni, Rodrigo L. UFMG-Universidade Federal de Minas Geais VERLab-Computer Vision and Robotics Laboratory Av. Antônio Carlos 6627 Belo Horizonte MG Brazil

ISBN: (纸本)0769523897

In this paper we study the use of computer vision techniques for for underwater visual tracking and counting of fishes in vivo. the methodology is based on the application of a Bayesian filtering technique that enables tracking of objects whose number may vary over time. Unlike existing fish-counting methods, this approach provides adequate means for the acquisition of relevant information about characteristics of different fish species such as swimming ability, time of migration and peak flow rates. the system is also able to estimate fish trajectories over time, which can be further used to study their behaviors when swimming in regions of interest. Our experiments demonstrate that the proposed method can operate reliably under severe environmental changes (e.g. variations in water turbidity) and handle problems such as occlusions or large inter-frame motions. the proposed approach was successfully validated with real-world video streams, achieving overall accuracy as high as 81%. © 2005 IEEE.

关键词： computer vision

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A maximum-likelihood approach for multiresolution W-operator design

A maximum-likelihood approach for multiresolution W-operator...

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SIBGRAPI 2005: 18th brazilian symposium on computer graphics and image processing - Conference Proceedings

作者： Vaquero, Daniel André Barrera, Junior Hirata Jr., Roberto USP-Universidade de São Paulo IME-Instituto de Matemática e Estatística Cidade Universitária Rua do Matão 1010 CEP: 05508-090 São Paulo SP Brazil

ISBN: (纸本)0769523897

the design of W-operators from a set of input/output examples for large windows is a hard problem. From the statistical standpoint, it is hard because of the large number of examples necessary to obtain a good estimate of the joint distribution. From the computational standpoint, as the number of examples grows memory and time requirements can reach a point where it is not feasible to design the operator. this paper introduces a technique for joint distribution estimation in W-operator design. the distribution is represented by a multiresolution pyramidal structure and the mean conditional entropy is proposed as a criterion to choose between distributions induced by different pyramids. Experimental results are presented for maximum-likelihood classifiers designed for the problem of handwritten digits classification. the analysis shows that the technique is interesting from the theoretical point of view and has potential to be applied in computer vision and image processing problems. © 2005 IEEE.

关键词： Distributed computer systems

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Signal processing method of holographic memory using image distortion correction and soft decision Viterbi decoding method

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 2005年第5B期44卷 3508-3512页

作者： Sato, D Nishimoto, K Katayanagi, Y Yamamoto, M Tokyo Univ Sci Grad Sch Ind Sci & Technol Noda Chiba 2788510 Japan

the signal quality of holographic memory is greatly lowered by the pixel mismatch between the charge-coupled device (CCD) and the reproduced image caused by image distortion. this paper discusses an approach to improve the signal quality by using two step decoding method. By this method, first, distortion correction is done to improve the degree of pixel mismatch to obtain better signal to noise ratio (SNR). then, to eliminate errors such as noise that cannot be removed by distortion correction, soft decision Viterbi decoding using the newly defined reliability is used to correct errors. the effectiveness of this two step decoding method was tested by computer simulation, and its effect to improve SNR and reduce errors was confirmed.

关键词： holographic memory distortion correction Viterbi decoding soft decision reliability modulation code

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