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16th brazilian symposium on computer graphics and image processing

作者： Silva, L Bellon, ORP Boyer, KL CEFET CPGEI Curitiba Parana Brazil

ISBN: (纸本)0769520324

this paper presents a new method for precise registration of multiple range images with low overlap based on Enhanced Genetic Algorithms (GAs). the proposed method minimizes the alignment error within the common overlap area among a set of views, which is computed by a novel robust evaluation metric, called the Surface Interpenetration Measure. Because they search in a space of transformations, GAs are capable of registering surfaces without need for prealignment, as opposed to methods based on the Iterative Closest Point (ICP) algorithm, the most popular to date. the experimental results confirm that the new method ensures more precise alignments than combined sequential pairwise alignments for multiview registration, providing accurate global alignment among overlapping views.

关键词： Area measurement Buildings Education Genetic algorithms image registration image restoration Iterative algorithms Iterative closest point algorithm Iterative methods Robustness

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image inpainting and denoising by nonlinear partial differential equations 16

Image inpainting and denoising by nonlinear partial differen...

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16th brazilian symposium on computer graphics and image processing

作者： Barcelos, CAZ Batista, MA Univ Fed Uberlandia FACOM BR-38400902 Uberlandia MG Brazil

ISBN: (纸本)0769520324

In this paper a new approach is presented for recovering shapes from noisy and damaged images as well as the filling in of missing information or the removal of objects from an image. the procedure allows for the denoising and inpainting of images simultaneously. the denoising is performed by the smoothing equation working inside and outside of the inpainting domain but in completely different ways. Inside the inpainting domain the smoothing is carried out by the Mean Curvature Flow, while the smoothing of the outside of the inpainting domain is carried out in a way to encourage smoothing within a region and discourage smoothing across boundaries. Besides smoothing, the approach here presented permits the transportation of available information from the outside towards the inside of the inpainting domain. this combination permits the simultaneous use of filling-in and differentiated smoothing of different regions of an image. the experimental results show the effective performance of the combination of these two procedures in image restoration.

关键词： Differential equations Filling image processing image restoration Noise reduction Noise shaping Partial differential equations Shape Smoothing methods Transportation

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Polygonization of volumetric reconstructions from silhouettes

Polygonization of volumetric reconstructions from silhouette...

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19th brazilian symposium on computer graphics and image processing (SIBGRAPI 2006)

作者： Montenegro, Anselmo Antunes Velho, Luiz Carvalho, Paulo C. P. Sossai, Jonas, Jr. Univ Estado Rio De Janeiro IME Dept Informat & Ciencia Comp Rio De Janeiro Brazil IMPA Inst Nac Matemat Pura Aplicada Rio De Janeiro Brazil

ISBN: (纸本)0769526861

In this work we propose a method for the polygonization of octree-based reconstructions by dual contouring. Dual contouring is an adaptive method for determining contiguous polygonal meshes from signed octrees. It determines the positioning of the vertices of the mesh by minimizing a quadratic error expressed in terms of hermitian data. In order to apply dual contouring on volumetric reconstruction from silhouettes we devised a method that is able to determine the discrete topology of the contour in relation to the octree cells, as well as the hermitian data corresponding to the intersections and normals of conic volumes whose intersection approximates a structure known as Visual Hull. Due to the discrete and extremely noisy nature of the data used in the reconstruction we had to devise a different criterion for mesh simplification that applies topological consistency tests only when the geometric error measure is beyond a given tolerance. We present results of the application of the proposed method in the extraction of a mesh corresponding to the surface of objects of a real scene.

关键词： image reconstruction

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Denoising and enhancing digital mammographic images for visual screening

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computerIZED MEDICAL IMAGING AND graphics 2006年第4期30卷 243-254页

作者： Scharcanski, Jacob Jung, Claudio Rosito Univ Fed Rio Grande do Sul BR-91501970 Porto Alegre RS Brazil Univ Vale Rio dos Sinos PIPCA Grad Sch Appl Comp UNISINOS BR-93022000 Sao Leopoldo RS Brazil

Dense regions in digital mammographic images are usually noisy and have low contrast, and their visual screening is difficult. this paper describes a new method for mammographic image noise suppression and enhancement, which can be effective particularly for screening image dense regions. Initially, the image is preprocessed to improve its local contrast and the discrimination of subtle details. Next, image noise suppression and edge enhancement are performed based on the wavelet transform. At each resolution, coefficients associated with noise are modelled by Gaussian random variables;coefficients associated with edges are modelled by Generalized Laplacian random variables, and a shrinkage function is assembled based on posterior probabilities. the shrinkage functions at consecutive scales are combined, and then applied to the wavelets coefficients. Given a resolution of analysis, the image denoising process is adaptive (i.e. does not require further parameter adjustments), and the selection of a gain factor provides the desired detail enhancement. the enhancement function was designed to avoid introducing artifacts in the enhancement process, which is essential in mammographic image analysis. Our preliminary results indicate that our method allows to enhance local contrast, and detect microcalcifications and other suspicious structures in situations where their detection would be difficult otherwise. Compared to other approaches, our method requires less parameter adjustments by the user. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： mammography contrast equalization image denoising image enhancement multiresolution analysis wavelets

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Visual Speech Recognition: a solution from feature extraction to words classification 16

Visual Speech Recognition: a solution from feature extractio...

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16th brazilian symposium on computer graphics and image processing

作者： Da Silveira, L Facon, J Borges, DL Cambury Coll Fac Cambury Goiania Go Brazil

ISBN: (纸本)0769520324

Audio-visual Speech Recognition has been an active area of research lately. A bit, and yet unsolved, part of this problem is the visual only recognition, or lip reading. Considering an image sequence of a person pronouncing a word, a full image analysis solution would have to segment the mouth area, extract relevant features, and use them to be able to classify the word from those visual features. In this paper we approach this problem by proposing a segmentation technique for the lips contours together with a set of features based on the extracted contours which is able to perform lip reading with promising results. We have collected visual speech sequences in our lab and show the results here for a set of ten words in brazilian Portuguese, spoken by different speakers in more than 150 samples. the approach can be extended and applied to other spoken languages as well.

关键词： Active shape model Automatic speech recognition Feature extraction image recognition image segmentation image sequences Lips Mouth Speech recognition Vocabulary

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Learning-based versus model-based log-polar feature extraction operators: A comparative study 16

Learning-based versus model-based log-polar feature extracti...

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16th brazilian symposium on computer graphics and image processing

作者： Gomes, HM Fisher, RB Univ Fed Campina Grande Dept Sistemas & Computacao BR-58109970 Campina Grande PB Brazil

ISBN: (纸本)0769520324

In this paper we compare two distinct primal sketch feature extraction operators: one based on neural network feature learning and the other based on mathematical models of the features. We tested both kinds of operator with a set of known, but previously untrained, synthetic features and, while varying their classification thresholds, measured the operator's false acceptance and false rejection errors. Results have shown that the model-based approach is more unstable and unreliable than the learning-based approach, which presented better results with respect to the number of correctly classified features.

关键词： Biosensors Computational geometry computer networks Feature extraction image sensors Machine vision Mathematical model Neural networks Sensor arrays Visual system

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An approach based on image processing techniques to segment lung region in chest X-ray images 34

An approach based on image processing techniques to segment ...

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34th SIBGRAPI Conference on graphics, Patterns and images (SIBGRAPI)

作者： de Menezes, Luiza C. de Araujo, Augusto R. V. F. Conci, Aura Univ Fed Fluminense Inst Comp BR-24210346 Niteroi RJ Brazil

ISBN: (纸本)9781665423540

Chest X-ray (CXR) images help specialists worldwide to diagnose lung diseases, such as tuberculosis and COVID-19. A primary step in an image-based diagnostic tool is to segment the region of interest. that facilitates the disease classification problem by reducing the amount of information to be processed. However, due to the noisy nature of CXRs, identifying the lung region can be a challenging task. this paper addresses the lung segmentation problem using a less costable computational process based on image analysis and mathematical morphology techniques. the proposed method achieved a specificity of 92.92%, a Jaccard index of 77.77%, and a Dice index of 87.37% on average.

关键词： graphics image segmentation image analysis Pulmonary diseases Lung Morphology Noise measurement

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Level lines continuation based digital inpainting

Level lines continuation based digital inpainting

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Barcelos, CAZ Batista, MA Martins, AM Nogueira, AC Universidade Federal de Goiás CAC Univ. Federal de Uberlândia Brazil Univ. Federal de Uberlândia 38.400-902 Uberlândia MG CX.P. 593 Brazil

ISBN: (纸本)0769522270

Inpainting digital models have been since the late 1990's a powerful image reconstruction tool for missing data. After the original work of Bertalmio, Sapiro, Caselles and Ballester [1] several different approaches have been used to tackle the problem. Some are based on Partial Differential Equations to model a transport process and a diffusion process, others are based on the Eider elastica functional. this paper presents a model using the level lines continuation to perform the filling-in of the inpainting domain D. the model is proposed in a way as to satisfy the "Connectivity Principle". the image u(x,y) is represented by a family of level lines and the missing part Of the image is filled-in by the propagation of the available surrounding information, from outside to inside of the inpainting domain D along the level lines of the image. After defining the domain D the restoration process becomes automatic and the final result u(x, y, t(n)) is carried out by the evolutionary process starting with the initial degraded image u(x, y, 0). Examples on real and textured images show the performance of this proposed model.

关键词： image reconstruction

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An image retrieval method based on factor analysis 16

An image retrieval method based on factor analysis

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16th brazilian symposium on computer graphics and image processing

作者： Machado, AMC Marinho, CNJ Campos, MFM Pontificia Univ Catolica Minas Gerais Belo Horizonte MG Brazil

ISBN: (纸本)0769520324

this article presents a new perspective to image retrieval based on multivariate factor analysis. Modern imaging modalities provide an overwhelming amount of information that cannot be appropriately handled without computerized tools. image retrieval methods aim to retrieve relevant images from a collected database, based on their content. the problem is made more difficult due to the high dimension of the variable space in which the images are represented. Factor analysis is able to minimize data redundancy and reveal hidden patterns. the characterization of complex features such as shape can be performed in a new lower-dimensional basis, in which the variables account for the correlation among regions of interest. the similarity between images is computed based on a set of vector variables obtained from image registration. Relevance feedback is used to iteratively determine the importance of each factor in the similarity function. the factors that are supposed to encompass the user's preferences are implicitly detected.

关键词： Content based retrieval Feedback image analysis image databases image registration image retrieval Information retrieval Pattern analysis Shape Spatial databases

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Interactive DTI-Based Constrained Tractography using OpenGL Pipeline 36

Interactive DTI-Based Constrained Tractography using OpenGL ...

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36th SIBGRAPI Conference on graphics, Patterns and images (SIBGRAPI)

作者： Wu Shin-Ting Voltoline, Raphael Benites, Rodrigo L. Univ Estadual Campinas Sch Elect & Comp Engn Campinas Brazil

ISBN: (纸本)9798350338737;9798350338720

this paper addresses the limitations of the DTI-based tracking algorithms commonly applied in routine clinical practice. Interactive tracking and rendering algorithms are presented using the OpenGL pipeline, allowing experts to explore, adjust, interpret, and validate the reconstructed pathways. the key features of our algorithms are fiber tracking preprocessing and separation of tracking and rendering stages.

关键词： Rendering (computer graphics)

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