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XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)最新文献

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New Tensorial Representation of Color Images: Tensorial Morphological Gradient Applied to Color Image Segmentation 彩色图像新的张量表示:张量形态梯度在彩色图像分割中的应用
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.27
L. Rittner, F. C. Flores, R. Lotufo
{"title":"New Tensorial Representation of Color Images: Tensorial Morphological Gradient Applied to Color Image Segmentation","authors":"L. Rittner, F. C. Flores, R. Lotufo","doi":"10.1109/SIBGRAPI.2007.27","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.27","url":null,"abstract":"This paper proposes a new Tensorial Representation of HSI color images, where each pixel is a 2 times 2 second order tensor, that can be represented by an ellipse. A proposed tensorial morphological gradient (TMG) is defined as the maximum dissimilarity over the neighborhood determined by a structuring element, and is used in the watershed segmentation framework. Many tensor dissimilarity functions are tested and other color gradients are compared. The comparison uses a new methodology for qualitative evaluation of color image segmentation by watershed, where the watershed lines of the n most significant regions are overlaid on the original image for visual comparison. Experiments show that the TMG using Frobenius norm dissimilarity function presents superior segmentation results, in comparison to other tested gradients.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"9 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128990665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 57
The Projection Explorer: A Flexible Tool for Projection-based Multidimensional Visualization 投影资源管理器:基于投影的多维可视化的灵活工具
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.21
F. Paulovich, Maria Cristina Ferreira de Oliveira, R. Minghim
{"title":"The Projection Explorer: A Flexible Tool for Projection-based Multidimensional Visualization","authors":"F. Paulovich, Maria Cristina Ferreira de Oliveira, R. Minghim","doi":"10.1109/SIBGRAPI.2007.21","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.21","url":null,"abstract":"Multidimensional projections map data points, defined in a high-dimensional data space, into a 1D, 2D or 3D representation space. Such a mapping may be typically achieved with dimensional reduction, clustering, or force directed point placement. Projections can be displayed and navigated by data analysts by means of visual representations, which may vary from points on a plane to graphs, surfaces or volumes. Typically, projections strive to preserve distance relationships amongst data points, as defined in the original space. Information loss is inevitable and the projection approach defines the extent to which the distance preserving goal is attained. We introduce PEx-the projection explorer - a visualization tool for mapping and exploration of high-dimensional data via projections. A set of examples - on both structured (table) and unstructured (text) data - illustrate how projection based visualizations, coupled with appropriate exploration tools, offer a flexible set-up for multidimensional data exploration. The projections in PEx handle relatively large data sets at a computational cost adequate to user interaction.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114412375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 105
Hardware-Assisted Point-Based Volume Rendering of Tetrahedral Meshes 四面体网格的硬件辅助点体绘制
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.20
Erik W. Anderson, Steven P. Callahan, C. Scheidegger, John M. Schreiner, Cláudio T. Silva
{"title":"Hardware-Assisted Point-Based Volume Rendering of Tetrahedral Meshes","authors":"Erik W. Anderson, Steven P. Callahan, C. Scheidegger, John M. Schreiner, Cláudio T. Silva","doi":"10.1109/SIBGRAPI.2007.20","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.20","url":null,"abstract":"Unstructured volume grids are ubiquitous in scientific computing, and have received substantial interest from the scientific visualization community. In this paper, we take a point-based approach to rendering unstructured grids. In particular, we present a novel method of approximating these irregular elements with point-based primitives amenable to existing hardware acceleration techniques. To improve interactivity to large datasets, we have adapted a level-of-detail strategy. We use a well-known quantitative metric to analyze the image quality achieved by the final rendering.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125402894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 18
An Exact and Efficient Algorithm for the Orthogonal Art Gallery Problem 正交美术馆问题的一种精确高效算法
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.15
Marcelo C. Couto, C. C. Souza, P. J. Rezende
{"title":"An Exact and Efficient Algorithm for the Orthogonal Art Gallery Problem","authors":"Marcelo C. Couto, C. C. Souza, P. J. Rezende","doi":"10.1109/SIBGRAPI.2007.15","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.15","url":null,"abstract":"In this paper, we propose an exact algorithm to solve the orthogonal art gallery problem in which guards can only be placed on the vertices of the polygon P representing the gallery. Our approach is based on a discretization of P into a finite set of points in its interior. The algorithm repeatedly solves an instance of the set cover problem obtaining a minimum set Z of vertices of P that can view all points in the current discretization. Whenever P is completely visible from Z, the algorithm halts; otherwise, the discretization is refined and another iteration takes place. We establish that the algorithm always converges to an optimal solution by presenting a worst case analysis of the number of iterations that could be effected. Even though these could theoretically reach 0(n4), our computational experiments reveal that, in practice, they are linear in n and, for n les 200, they actually remain less than three in almost all instances. Furthermore, the low number of points in the initial discretization, 0(n2), compared to the possible O(n4) atomic visibility polygons, renders much shorter total execution times. Optimal solutions found for different classes of instances of polygons with up to 200 vertices are also described.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116977062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 28
A New Method for Detection of Active Brain Regions with Event-Related fMRI Time Series Analysis 基于事件相关fMRI时间序列分析的脑活动区域检测新方法
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.34
J. Duque, M. Sturzbecher, D. Araujo, J. C. Felipe
{"title":"A New Method for Detection of Active Brain Regions with Event-Related fMRI Time Series Analysis","authors":"J. Duque, M. Sturzbecher, D. Araujo, J. C. Felipe","doi":"10.1109/SIBGRAPI.2007.34","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.34","url":null,"abstract":"Functional magnetic resonance imaging (fMRI) has been applied with several purposes in clinical environment as well as in basic neuroscience studies. The main purpose of fMRI is to map brain activity, which is achieved by applying statistical methods to time series of each voxel intensity, related to changes in blood oxygen level, in response to a short stimulus. In this work, we propose a new method for the analysis of event-related fMRI based in the use of the dynamic time warping technique to compare pixel intensity time series. The results show the ability to discriminate activated brain regions, when subjects were engaged in a motor task.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114074486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Robust and Adaptive Surface Reconstruction using Partition of Unity Implicits 基于统一隐式分割的鲁棒自适应曲面重构
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.8
J. P. Gois, V. Polizelli-Junior, Tiago Etiene, Eduardo Tejada, A. C. Filho, T. Ertl, L. G. Nonato
{"title":"Robust and Adaptive Surface Reconstruction using Partition of Unity Implicits","authors":"J. P. Gois, V. Polizelli-Junior, Tiago Etiene, Eduardo Tejada, A. C. Filho, T. Ertl, L. G. Nonato","doi":"10.1109/SIBGRAPI.2007.8","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.8","url":null,"abstract":"Implicit surface reconstruction from unorganized point sets has been recently approached with methods based on multi-level partition of unity. We improve this approach by addressing local approximation robustness and iso-surface extraction issues. Our method relies on the J1 A triangulation to perform both the spatial subdivision and the iso-surface extraction. We also make use of orthogonal polynomials to provide adaptive local approximations in which the degree of the polynomial can be adjusted to accurately reconstruct the surface locally. Finally, we compare our results with previous work to demonstrate the robustness of our method.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122130045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 10
Color Mathematical Morphology Based on Partial Ordering of Spectra 基于光谱偏序的颜色数学形态学
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.46
M. C. d'Ornellas, J. A. B. D. Costa
{"title":"Color Mathematical Morphology Based on Partial Ordering of Spectra","authors":"M. C. d'Ornellas, J. A. B. D. Costa","doi":"10.1109/SIBGRAPI.2007.46","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.46","url":null,"abstract":"Mathematical morphology is based on the principle of ordering. There is no natural way to order colors (being triplets of scalars). A lot of different ordering relations have been proposed in the literature, most on an ad-hoc basis. In this paper, we propose an ordering relation for colors that is based on the natural (i.e. physically plausible) ordering of spectra. Therefore, we ensure that the ordering is independent of the chosen color parameterization. We discuss that part of colorimetric theory that enables us to reconstruct the spectrum given the three color parameters. Furthermore, we present the very basics of the algebraic framework of mathematical morphology. This allows us to embed the presented ordering of colors within the morphological framework such that we can fully exploit the possibilities to define morphological image operators working on color images.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131600751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 14
An Opto-Mechanical Apparatus for Binocular Helmholtz Stereopsis in Static and Dynamic Scenes 静态和动态场景下双目亥姆霍兹立体视觉的光机械装置
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.45
Wagner Barros, R. Carceroni, Lara C. R. Coelho, J. P. Queiroz-Neto
{"title":"An Opto-Mechanical Apparatus for Binocular Helmholtz Stereopsis in Static and Dynamic Scenes","authors":"Wagner Barros, R. Carceroni, Lara C. R. Coelho, J. P. Queiroz-Neto","doi":"10.1109/SIBGRAPI.2007.45","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.45","url":null,"abstract":"This paper presents an opto-mechanical apparatus for binocular stereopsis based on the Helmholtz reciprocity principle. The proposed system makes it possible to obtain three-dimensional models of static and dynamic scenes with arbitrary reflectance properties including highly specular surfaces and holograms. We also propose an empirical methodology for the treatment of occlusions that improves the description of half-occluded areas. Experimental results with real images validate the proposed system.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130306949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 5
Feature selection with equalized salience measures and its application to segmentation 均衡显著性特征选择及其在分割中的应用
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.17
Davi P. Santos, João Batista Neto
{"title":"Feature selection with equalized salience measures and its application to segmentation","authors":"Davi P. Santos, João Batista Neto","doi":"10.1109/SIBGRAPI.2007.17","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.17","url":null,"abstract":"Segmentation is a crucial step in computer vision in which texture plays an important role. The existence of a large amount of methods from which texture can be computed is, sometimes, a hurdle to overcome when it comes to modeling solutions for texture-based segmentation. Following the excellence of the natural vision system and its generality, this work has adopted a feature selection method based on salience of synaptic connections of a Multilayer Perceptron neural network. Unlike traditional approaches, this paper introduces an equalization scheme to salience measures which contributed to significantly improve the selection of the most suitable features and, hence, yield better segmentation. The proposed method is compared with exhaustive search according to the Jeffrey-Matusita distance criterion. Segmentation for images of natural scenes has also been provided as a probable application of the method.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"25 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132089393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 19
A Bucket Grid Structure to Speed Up Table Lookup in Gauge-Based Photometric Stereo 在基于量规的光度立体测量中加速表查找的桶网格结构
XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007) Pub Date : 2007-10-07 DOI: 10.1109/SIBGRAPI.2007.16
H. C. G. Leitão, R. Saracchini, J. Stolfi
{"title":"A Bucket Grid Structure to Speed Up Table Lookup in Gauge-Based Photometric Stereo","authors":"H. C. G. Leitão, R. Saracchini, J. Stolfi","doi":"10.1109/SIBGRAPI.2007.16","DOIUrl":"https://doi.org/10.1109/SIBGRAPI.2007.16","url":null,"abstract":"In this paper, we show how to speed up the table lookup step in gauge-based multi-image photometric stereo. In that step, one must find a pixel of a gauge object, of known shape and color, whose appearance under m different illumination fields is similar to that of a given scene pixel. This search reduces to finding the closest match to a given m- vector in a table with a thousand or more m-vectors. Our speed-up method exploits the fact that the table is in fact a fairly flat two-dimensional manifold in m-dimensional space, so that the search can be efficiently solved with a two-dimensional bucket grid structure.","PeriodicalId":434632,"journal":{"name":"XX Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI 2007)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128260685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
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