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20th brazilian symposium on computer graphics and image processing, sibgrapi 2007

作者： Santos, Carlos S. Hirata, Nina S. T. Hirata Jr., Roberto Department of Computer Science Institute of Mathematics and Statistics University of Sacombining Double Acute Accento Paulo Rua do Matacombining double acute accento 1010 05508-090 Sacombining double acute accento Paulo Brazil

ISBN: (纸本)0769529968

We address the problem of binary image operator design over large windows by breaking it into two phases. Firstly, we design several operators over small sub-windows of the main window. the outputs of these first level operators are then combined into a global operator. We devise a heuristic, motivated by Information theory, for breaking the main window into sub-windows. Preliminary results show that the proposed scheme improves operator performance over single-level operators. © 2007 IEEE.

关键词： Binary images

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Graph-based object tracking using structural pattern recognition

Graph-based object tracking using structural pattern recogni...

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20th brazilian symposium on computer graphics and image processing, sibgrapi 2007

作者： Graciano, Ana B. V. Cesar Jr., Roberto M. Bloch, Isabelle Institute of Mathematics and Statistics - USP Department of Computer Science Rua do Matão 1010 São Paulo SP 05508-900 Brazil Dept. TSI GET-ENST CNRS - UMR 5141 LTCI 46 Rue Barrault F-75634 Cedex 13 Paris France

ISBN: (纸本)0769529968

this paper proposes a model-based methodology for recognizing and tracking objects in digital image sequences. Objects are represented by attributed relational graphs (or ARGs), which carry both local and relational information about them. the recognition is performed by inexact graph matching, which consists in finding an approximate homomorphism between ARGs derived from an input video and a model image. Searching for a suitable homomorphism is achieved through a tree-search optimization algorithm and the minimization of a pre-defined cost function. Motion smoothness between successive frames is exploited to achieve the recognition over the whole sequence, with improved spatio-temporal coherence. © 2007 IEEE.

关键词： Cost functions

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Superpixel segmentation: from theory to applications 36

Superpixel segmentation: from theory to applications

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

作者： Borlido, Isabela Belem, Felipe Melo, Leonardo theodoro, Taylla M. Silva, Ilan F. do Patrocinio, Zenilton K. G., Jr. Falcao, Alexandre X. Guimardes, Silvio Jamil F. Pontifical Catholic Univ Minas Gerais PUC Minas Comp Sci Dept DCC Image & Multimedia Data Sci Lab IMSci Belo Horizonte MG Brazil Univ Estadual Campinas Inst Comp IC Lab Image Data Sci LIDS UNICAMP Campinas Brazil

ISBN: (纸本)9798350338737;9798350338720

Superpixel segmentation consists of partitioning images into regions composed of similar and connected pixels. Its methods have been widely used in many computer vision applications since it allows for reducing the workload, removing redundant information, and preserving regions with meaningful features. Due to the rapid progress in this area, the literature fails to catch up on more recent works among the compared ones and to categorize the methods according to all existing strategies. We revisit the recent and popular literature according to our taxonomy and evaluate 20 strategies based on nine criteria: connectivity, compactness, delineation, control over the number of superpixels, color homogeneity, robustness, running time, stability, and visual quality. thus, this document presents a proposal for a tutorial to be presented at sibgrapi 2023.

关键词： Superpixel Trends Applications

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Multiple testing correction in medical image analysis

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 107-117页

作者： Machado, Alexei Manso Correa Pontifical Catholic Univ Minas Gerias BR-30535610 Belo Horizonte MG Brazil

We present a novel method for correcting the significance level of hypothesis testing that requires multiple comparisons. It is based on the spectral graph theory, in which the variables are seen as the vertices of a complete undirected graph and the correlation matrix as the adjacency matrix that weights its edges. the method increases the statistical power of the analysis by refuting the assumption of independence among variables, while keeping the probability of false positives low. By computing the eigenvalues of the correlation matrix, it is possible to obtain valuable information about the dependence levels among the variables of the problem, so that the effective number of independent variables can be estimated. the method is compared to other available models and its effectiveness illustrated in case studies involving high-dimensional sets of variables.

关键词： hypothesis testing Bonferroni correction spectral graph theory

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Convergence of map seeking circuits

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 235-248页

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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Viscosity solutions of a level-set method for anisotropic geometric diffusion in image processing

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 205-217页

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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Automatic image segmentation by tree pruning

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 141-162页

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

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 163-183页

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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Multiple testing correction in medical image analysis

Multiple testing correction in medical image analysis

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