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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： A.M. Correa Machado M.F. Montenegro CAmpos J. Gee Departmento de Ciência da Computação Pontificia Universidade Católica de Minas Gerais Belo Horizonte Minas Gerais Brazil Departmento de Ciência da Computação Universidade Federal de Minas Gerais Belo Horizonte Minas Gerais Brazil Department of Radiology University of Pennsylvania Philadelphia PA USA

In this work, we present a method which is able to relate different MR sensors with respect to intensity distortions in the output images. For the important problem of image registration, the method makes possible a principled approach to likelihood modeling or the construction of similarity metrics. Likelihood models can be used as prior knowledge of the relationship between intensities in both images, providing a fundamental information resource for image registration. A poor model of the intensity mapping for the image pair to be matched may lead to false matches, regardless of the prior morphological constraints assumed and will bias all subsequent analyses. A formal analysis of robustness under different kinds of noise is also provided and the findings compared to other relevant similarity metrics. Experiments are controlled based on the application of synthetic spatial and intensity deformations that guarantee a fiducial basis for comparison.

关键词： Magnetic resonance imaging image registration image sensors Magnetic sensors image analysis Noise robustness Testing Deformable models Radiology Computational Intelligence Society

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An off-line signature verification system using hidden Markov model and cross-validation

An off-line signature verification system using hidden Marko...

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： E.J.R. Justino A. El Yacoubi F. Bortolozzi R. Sabourin PUCPR-Pontifícia Universidade Católica do Paraná Curitiba Parana Brazil Pontificia Universidade Catolica do Parana Curitiba PR BR

The main objective is to present an off-line signature verification system. It is basically divided into three parts. The first demonstrates a pre-processing process, a segmentation process and a feature extraction process, in which the main aim is to obtain the maximum performance quality of the process of verification of random falsifications, in the false acceptance and false rejection concept. The second presents a learning process based on HMM, where the aim is obtaining the best model. That is, one that is capable of representing each writer's signature, absorbing yet at the same time discriminating, at most the intrapersonal and interpersonal variation. The third presents a signature verification process that uses the models generated by the learning process without using any prior knowledge of test data, in other words, using an automatic derivation process of the decision thresholds.

关键词： Handwriting recognition Hidden Markov models Pattern recognition Feature extraction Speech recognition Automatic testing Neural networks Euclidean distance image matching Text recognition

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International symposium on image and Signal processing and Analysis, ISPA

International Symposium on Image and Signal Processing and A...

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1st International Workshop on image and Signal processing and Analysis, IWISPA 2000

ISBN: (纸本)9539676924

The proceedings contain 41 papers. The topics discussed include: digital visual information processing: adding vision and graphics;polynomial filters for image and video processing;edge-preserving neural network model for image restoration;simultaneous estimation of PSF and global frame shifts at lower S/N ratios;generalization of the Fourier domain watermarking to the space/spatial frequency domain;restoration of images blurred by circular motion;background-foreground segmentation based on dominant motion estimation and static segmentation;environment based clustering: a new approach;local similarity measures for multimodal image matching;combined invariants to convolution and rotation;image classification based on color and texture analysis;and detection and classification of MS using magnetization transfer ratio images.

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A visual attention model for tracking regions based on color correlograms

A visual attention model for tracking regions based on color...

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： L.L. Galdino D.L. Borges Escola de Engenharia Eléctrica e de Computação Laboratório de Sistemas Inteligentes Universidade Federal de Goiás Goiania Goias Brazil

The amount of information contained in a single color shot of a scene is extreme considering the variety of tasks that can be performed relying on visual data only. For the purpose of analyzing scenes dynamically, where objects come and go, one has to work under a structure of a visual attention model which prioritizes what type of visual data the system has to follow. This paper presents a novel visual attention model for region tracking based on color correlograms. First, a reference frame is picked and it is segmented for the most significant color regions present in the shot. Color correlograms are then run on every frame after in order to provide spectral and spatial information, for the visual attention control, about the past and the new objects appearing on the scenes. The visual attention (VA) model then keeps track of old and new color regions appearing on the scene until a different frame is chosen. We have run experiments which show the performance of this proposed VA model.

关键词： Layout computer vision Color Navigation Animation Information analysis Solid modeling Object recognition Uncertainty Feature extraction

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Time-critical rendering of irregular grids

Time-critical rendering of irregular grids

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： R. Farias J.S.B. Mitchell C.T. Silva B. Wylie Dept. of Appl. Math. & Stat. State Univ. of New York Stony Brook NY USA Department of Applied Mathematics and Statistics State University of New York Stony Brook Stony Brook NY USA AT and T Research Laboratories Florham Park NJ USA

Many papers have presented rendering techniques and simplification ideas with the objective of speeding up image generation for irregular grid data sets. For large data sets, however, even the current fastest algorithms are known to require seconds to generate each image, making real time analysis of such data sets very difficult, or even impossible, unless one has access to powerful and expensive computer hardware. In order to synthesize a system for handling very large data set analysis, we have assembled algorithms for rendering, simplification and triangulation, and added to them some optimizations. We have made some improvements on one of the best current algorithms for rendering irregular grids, and added to it some simple approximation methods in both image and object space, resulting in a system that achieves high frame rates, even on slow computers without any specific graphic hardware. The algorithm adapts itself to the time budget it has available for each image generation, using hierarchical representations of the mesh for faster delivery of images when transformations are imposed to the data. When given additional time, the algorithm generates finer images, obtaining the precise final image if given sufficient time. We were able to obtain frame rates of the order of 5 Hz for medium-sized data sets, which is about 20 times faster than previous rendering algorithms. With a trade-off between image accuracy and speed, similar frame rates can be achieved on different computers.

关键词： Time factors Rendering (computer graphics) image generation Data analysis Algorithm design and analysis Hardware Power generation image analysis Assembly systems Approximation algorithms

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Directional analysis of images with Gabor wavelets

Directional analysis of images with Gabor wavelets

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： R.M. Rangayyan R.J. Ferrari J.E.L. Desautels A.F. Frere Department of Electrical and Computer Engineering University of Calgary Alberta Canada Department of Electrical Engineering University of São Paulo Sao Carlos SP Brazil Alberta Cancer Board Alberta Canada Nucleus of Science and Technology University of Mogi das Cruzes Mogi das Cruzes SP Brazil

The paper presents a new scheme for analysis of linear directional components in images by using a multiresolution representation based on Gabor wavelets. A dictionary of Gabor filters with varying tuning frequency and orientation, specifically designed in order to reduce the redundancy in the wavelet-based representation, is applied to the given image. The filter responses for different scales and orientation are analyzed by using the Karhunen-Loeve (KL) transform and Otsu's (1979) method of thresholding. The KL transform is applied to select the principal components of the filter responses, preserving only the most relevant directional elements appearing at all scales. The first N principal components, thresholded by using Otsu's method, are used to reconstruct the magnitude and phase of the directional components of the image. Rose diagrams computed from the phase images are used for quantitative and qualitative analysis of the oriented patterns. The proposed scheme is applied to the analysis of asymmetry between left and right mammograms. For this purpose, a set of three features is extracted from the Rose diagrams and used in a parametric statistical classifier. A total of 80 images from 20 normal cases, 14 asymmetric cases, and 6 distortion cases from the Mini-MIAS database were used to evaluate the scheme using the leave-one-out methodology, resulting in an average diagnostic accuracy of 72.5%.

关键词： image analysis Wavelet analysis Gabor filters Karhunen-Loeve transforms image resolution Dictionaries Tuning Frequency image reconstruction Pattern analysis

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Target search by bottom-up and top-down fuzzy information

Target search by bottom-up and top-down fuzzy information

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： E.M. de Almeida Neves J.E. Borelli A. Gonzaga Physics Institute at Sāo Carlos University of São Paulo Brazil School of Engineering at Sāo Carlos Department of Electrical Engineering University of São Paulo Sao Paulo Brazil

One of the basic tasks assigned to the attentional mechanism is to decide which location in the visual field we must pay attention first. An object containing a distinctive feature can attract attention in a bottom-up way. By comparing one object with the others present in the scene, bottom-up conspicuity features are used to guide attention to the most different object. Top-down hints are based on the previous knowledge about the objects or on which features are important to locate them and also have a large influence on the attended locations. Inspired by the mechanisms of human visual attention we developed a new methodology to integrate bottom-up and top-down information by using a fuzzy net containing three fuzzy subsystems. The first bottom-up subsystem allow us to combine features and infer with great flexibility some intuitive decision rules based on the visual perception principles such as the Gestalt laws. The second top-down subsystem combines different features according to the relevance of them in different tasks. Finally, the last subsystem integrates the information of the previous systems and gives a general salience index. The new methodology was tested in geometrical objects considering the features that attract attention to human beings.

关键词： Humans Layout Visual perception Interference Physics Testing Psychology Retina Information processing

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Fast perception-based depth of field rendering 00

Fast perception-based depth of field rendering

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2000 ACM symposium on Virtual Reality Software and Technology, VRST 2000

作者： Mulder, Jurriaan D. Van Liere, Robert Center for Mathematics and Computer Science Kruislaan 413 Amsterdam1098 SJ Netherlands

ISBN: (纸本)1581133162

Current algorithms to create depth of field (DOF) effects are either too costly to be applied in VII, systems, or they produce inaccurate results. In this paper, we present a new algorithm to create DOF effects. The algorithm is based on two techniques: one of high accuracy and one of high speed but less accurate. The latter is used to create DOF effects in the peripheral viewing area where accurate results are not necessary. The first is applied to the viewing volume focussed at by the viewer. Both techniques make extensive use of rendering hardware, for texturing as well as image processing. The algorithm presented in this paper is an improvement over other (fast) DOF algorithms in that it is faster and provides better quality DOF effects where it matters most. © ACM 2000.

关键词： Virtual reality

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Digital visual information processing: adding vision and graphics

Digital visual information processing: adding vision and gra...

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International symposium on image and Signal processing and Analysis

作者： F.W. Leberl Institute for Computer Graphics and Vision Graz University of Technology Graz Austria

ISBN: (纸本)9539676924

Models of the real world are at least 3-dimensional and require the technologies of image processing and computer graphics. We see the processing of images, be they of the real world or of models in a computer, as one and the same basic technology, namely "digital visual information processing". This paper seeks to illustrate and justify this point-of-view by means of examples taken mostly from the work at the author's institute.

关键词： Information processing computer graphics Rendering (computer graphics) Pipelines computer vision Signal processing image analysis Signal analysis image sequence analysis image texture analysis

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Automatic generation of virtual woodblocks and multicolor woodblock printing

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computer graphics FORUM 2000年第3期19卷 C51-+页

作者： Mizuno, S Kasaura, T Okouchi, T Yamamoto, S Okada, M Toriwaki, J Toyohashi Univ Technol Toyohashi Aichi Japan Sony Corp Tokyo Japan Chubu Univ Kasugai Aichi 487 Japan Nagoya Univ Nagoya Aichi Japan

In this paper we study a method to synthesize a multicolor virtual woodblock print by using several virtual woodblocks. It consists of two sections: canting and printing, to synthesize a virtual print. In the carving section, virtual woodblocks are generated by a user with supporting of an automatically carving method based on feature extraction of a gray value image. And woodblocks are also generated automatically by using a full-color image as a draft. In the printing section, a "paper sheet", a "printing brush " and "ink" are prepared in addition to the "woodblock " in the virtual space and the user synthesizes a woodblock print interactively. As the printing factors, a color of ink, a moisture value and a grain change the finish of the print. Using several virtual woodblocks and printing to a paper sheet in succession, a printing image of each woodblock is combined based on the printing factors and a multicolor virtual prints is synthesized.

关键词： DIGITAL image processing computer graphics computer simulation PRINTING

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