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

作者： Preusser, Tobias Univ Bremen Ctr Comp Syst & Visualizat CeVis D-28359 Bremen Germany

We discuss the existence of viscosity solutions for a class of anisotropic level-set methods which can be seen as an extension of the mean-curvature motion with a nonlinear anisotropic diffusion tensor. In an earlier work (Mikula et al. in Comput. Vis. Sci. 6(4):197-209, [2004];Preusser and Rumpf in SIAM J. Appl. Math. 62(5):1772-1793, [2002]) we have applied such methods for the denoising and enhancement of static images and image sequences. the models are characterized by the fact that-unlike the mean-curvature motion-they are capable of retaining important geometric structures like edges and corners of the level-sets. the article reviews the definition of the model and discusses its geometric behavior. the proof of the existence of viscosity solutions for these models is based on a fixed point argument which utilizes a compactness property of the diffusion tensor. For the application to image processing suitable regularizations of the diffusion tensor are presented for which the compactness assumptions of the existence proof hold. Finally, we consider the half relaxed limits of the solutions of auxiliary problems to show the compactness of the solution operator and thus the existence of a solution to the original problem.

关键词： image processing anisotropic diffusion level set method viscosity solution half relaxed limits

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Reconstruction of 3D object meshes from silhouette images

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 119-130页

作者： Montenegro, Anselmo Antunes Velho, Luiz Carvalho, Paulo C. P. Sossai, Jonas, Jr. Univ Fed Fluminense Dept Ciencia Comp BR-24210240 Niteroi RJ Brazil Inst Nacl Matemat Pura & Aplicada Rio De Janeiro Brazil

In this work we propose a method for computing mesh representations of 3D objects reconstructed from a set of silhouette images. Our method is based on the polygonization of volumetric reconstructions by using a modified version of the dual contouring method. 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 surface in relation to the octree cells. We also developed a new scheme for computing hermitian data representing the intersections of conic volumes with the octree cells and their corresponding normals with subpixel accuracy. 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： polygonization of volumetric reconstructions mesh reconstruction from silhouettes dual contouring octree polygonization Visual hulls image-based modeling mesh simplification

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Generalized rigid and generalized affine image registration and interpolation by geometric multigrid

Generalized rigid and generalized affine image registration ...

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

作者： Keeling, Stephen L. Karl Franzens Univ Graz Inst Math & Wissenschaftliches Rechmen A-8010 Graz Austria

Generalized rigid and generalized affine registration and interpolation obtained by finite displacements and by optical flow are here developed variationally and numerically as well as with respect to a geometric multigrid solution process. For high order optimality systems under natural boundary conditions, it is shown that the convergence criteria of Hackbusch (Iterative Solution of Large Sparse Systems of Equations. Springer, Berlin, 1993) are met. Specifically, the Galerkin formalism is used together with a multi-colored ordering of unknowns to permit vectorization of a symmetric successive over-relaxation on image processing systems. the geometric multigrid procedure is situated as an inner iteration within an outer Newton or lagged diffusivity iteration, which in turn is embedded within a pyramidal scheme that initializes each outer iteration from predictions obtained on coarser levels. Differences between results obtainable by finite displacements and by optical flows are elucidated. Specifically, independence of image order can be shown for optical flow but in general not for finite displacements. Also, while autonomous optical flows are used in practice, it is shown explicitly that finite displacements generate a broader class of registrations. this work is motivated by applications in histological reconstruction and in dynamic medical imaging, and results are shown for such realistic examples.

关键词： generalized rigid generalized affine image registration image interpolation geometric multigrid

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Convergence of map seeking circuits

Convergence of map seeking circuits

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

作者： Gedeon, Tomas Arathorn, David Montana State Univ Dept Math Sci Bozeman MT 59715 USA Montana State Univ Gen Intelligence Corp Ctr Computat Biol Bozeman MT 59715 USA

the map-seeking circuit (MSC) is an explicit biologically-motivated computational mechanism which provides practical solution of problems in object recognition, image registration and stabilization, limb inverse-kinematics and other inverse problems which involve transformation discovery. We formulate this algorithm as discrete dynamical system on a set Delta = Pi(L)(l=1)Delta((l)), where each Delta((l)) is a compact subset of a nonnegative orthant of R-n, and show that for an open and dense set of initial conditions in Delta the corresponding solutions converge to either a vector with unique nonzero element in each Delta((l)) or to a zero vector. the first result implies that the circuit finds a unique best mapping which relates reference pattern to a target pattern;the second result is interpreted as "no match found". these results verify numerically observed behavior in numerous practical applications.

关键词： map seeking circuits computer vision dynamical systems Lyapunov function

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Automatic image segmentation by tree pruning

Automatic image segmentation by tree pruning

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

作者： Bergo, Felipe P. G. Falcao, Alexandre X. Miranda, Paulo A. V. Rocha, Leonardo M. Univ Estadual Campinas LIV Inst Comp BR-13083970 Campinas SP Brazil Univ Estadual Campinas DECOM FEEC BR-13083970 Campinas SP Brazil

the image Foresting Transform (IFT) is a tool for the design of image processing operators based on connectivity, which reduces image processing problems into an optimum-path forest problem in a graph derived from the image. A new image operator is presented, which solves segmentation by pruning trees of the forest. An IFT is applied to create an optimum-path forest whose roots are seed pixels, selected inside a desired object. In this forest, object and background are connected by optimum paths (leaking paths), which cross the object's boundary through its "most weakly connected" parts (leaking pixels). these leaking pixels are automatically identified and their subtrees are eliminated, such that the remaining forest defines the object. Tree pruning runs in linear time, is extensible to multidimensional images, is free of ad hoc parameters, and requires only internal seeds, with little interference from the heterogeneity of the background. these aspects favor solutions for automatic segmentation. We present a formal definition of the obtained objects, algorithms, sufficient conditions for tree pruning, and two applications involving automatic segmentation: 3D MR-image segmentation of the human brain and image segmentation of license plates. Given that its most competitive approach is the watershed transform by markers, we also include a comparative analysis between them.

关键词： image segmentation graph-search algorithms image foresting transform image processing watershed transform

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Mumford-Shah on the move: Region-based segmentation on deforming manifolds with application to 3-D reconstruction of shape and appearance from multi-view images

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 219-234页

作者： Jin, Hailin Yezzi, Anthony J. Soatto, Stefano Adobe Syst Inc Off Tech San Jose CA 95110 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA Univ Calif Los Angeles Dept Comp Sci Los Angeles CA 90025 USA

We address the problem of estimating the shape and appearance of a scene made of smooth Lambertian surfaces with piecewise smooth albedo. We allow the scene to have self-occlusions and multiple connected components. this class of surfaces is often used as an approximation of scenes populated by man-made objects. We assume we are given a number of images taken from different vantage points. Mathematically this problem can be posed as an extension of Mumford and Shah's approach to static image segmentation to the segmentation of a function defined on a deforming surface. We propose an iterative procedure to minimize a global cost functional that combines geometric priors on both the shape of the scene and the boundary between smooth albedo regions. We carry out the numerical implementation in the level set framework.

关键词： variational methods Mumford-Shah functional image segmentation multi-view stereo level set methods curve evolution on surfaces dense shape reconstruction structure from motion visibility

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Reconstruction of 3D object meshes from silhouette images

Reconstruction of 3D object meshes from silhouette images

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

关键词： polygonization of volumetric reconstructions mesh reconstruction from silhouettes dual contouring octree polygonization Visual hulls image-based modeling mesh simplification

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Mumford-Shah on the move: Region-based segmentation on deforming manifolds with application to 3-D reconstruction of shape and appearance from multi-view images

Mumford-Shah on the move: Region-based segmentation on defor...

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

关键词： variational methods Mumford-Shah functional image segmentation multi-view stereo level set methods curve evolution on surfaces dense shape reconstruction structure from motion visibility

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Proceedings - SIBGRAPI 2006: XIX brazilian symposium on computer graphics and image processing

Proceedings - SIBGRAPI 2006: XIX Brazilian Symposium on Comp...

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

ISBN: (纸本)0769526861

the proceedings contain 44 papers. the topics discussed include: dealing with multi-scale depth changes and motion in depth edge detection;parabolic polygons and discrete affine geometry;actively illuminated objects using graph-cuts;a computer-assisted colorization algorithm based on topological difference;increasing statistical power in medical image analysis;non-extensive entropy for CAD systems of breast cancer images;hardware-assisted rendering of CSG models;plausible image based soft shadows using occlusion textures;directing the attention of a wearable camera by pointing gestures;subspace hierarchical particle filter;robust adaptive meshes for implicit surfaces;a statistical discriminant model for face interpretation and reconstruction;vector field reconstruction from sparse samples with applications;motion segmentation using mathematical morphology;detection of unusual motion using computer vision;and video segmentation by supervised learning.

关键词： computer graphics

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Proceedings - SIBGRAPI 2006: XIX brazilian symposium on computer graphics and image processing: Preface

Brazilian Symposium of Computer Graphic and Image Processing

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brazilian symposium of computer Graphic and image processing 2006年 9-9页

作者： Oliveira, Manuel M. Carceroni, Rodrigo L.

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