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  • 1. Alexandre, Enrique
    et al.
    Gil-Pita, Roberto
    Raspaud, Martin
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    On the Evaluation of the Performance of Music Instrument Classification Systems2008In: 10th Meeting of the AES Portugal, 2008Conference paper (Other academic)
  • 2.
    Alsam, Ali
    et al.
    Gjøvik University College, Norway.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Calibrating color cameras using metameric blacks2007In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 24, no 1, p. 11-17Article in journal (Refereed)
    Abstract [en]

    Spectral calibration of digital cameras based on the spectral data of commercially available calibration charts is an ill-conditioned problem that has an infinite number of solutions. We introduce a method to estimate the sensor's spectral sensitivity function based on metamers. For a given patch on the calibration chart we construct numerical metamers by computing convex linear combinations of spectra from calibration chips with lower and higher sensor response values. The difference between the measured reflectance spectrum and the numerical metamer lies in the null space of the sensor. For each measured spectrum we use this procedure to compute a collection of color signals that lie in the null space of the sensor. For a collection of such spaces we compute the robust principal components, and we obtain an estimate of the sensor by computing the common null space spanned by these vectors. Our approach has a number of advantages over standard techniques: It is robust to outliers and is not dominated by larger response values, and it offers the ability to evaluate the goodness of the solution where it is possible to show that the solution is optimal, given the data, if the calculated range is one dimensional. © 2006 Optical Society of America.

  • 3.
    Alsam, Ali
    et al.
    Gjövik University College, Norway.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Calibrating Color Cameras Using Metameric Blacks2006In: European Conference on Color in Graphics, Imaging and Vision,2006, 7003 Kilworth Lane, Springfield, VA 22151 USA: The Society for Imaging Science and Technology , 2006, p. 75-Conference paper (Refereed)
    Abstract [en]

    Spectral calibration of digital cameras based on the spectral data of commercially available calibration charts is an illconditioned problem which has an infinite number of solutions. To improve upon the estimate, different constraints are commonly employed. Traditionally such constraints include: nonnegativity, smoothness, uni-modality and that the estimated sensors results in as good as possible response fit. In this paper, we introduce a novel method to solve a general ill-conditioned linear system with special focus on the solution of spectral calibration. We introduce a new approach based on metamerism. We observe that the difference between two metamers (spectra that integrate to the same sensor response) is in the null-space of the sensor. These metamers are used to robustly estimate the sensor-s null-space. Based on this nullspace, we derive projection operators to solve for the range of the unknown sensor. Our new approach has a number of advantages over standard techniques: It involves no minimization which means that the solution is robust to outliers and is not dominated by larger response values. It also offers the ability to evaluate the goodness of the solution where it is possible to show that the solution is optimal, given the data, if the calculated range is one dimensional. When comparing the new algorithm with the truncated singular value decomposition and Tikhonov regularization we found that the new method performs slightly better for the training set with noticeable improvements for the test data. 

  • 4.
    Andersson, Thord
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Läthén, Gunnar
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    A Fast Optimization Method for Level Set Segmentation2009In: Image Analysis: 16th Scandinavian Conference, SCIA 2009, Oslo, Norway, June 15-18, 2009. Proceedings / [ed] A.-B. Salberg, J.Y. Hardeberg, and R. Jenssen, Springer Berlin/Heidelberg, 2009, p. 400-409Conference paper (Refereed)
    Abstract [en]

    Level set methods are a popular way to solve the image segmentation problem in computer image analysis. A contour is implicitly represented by the zero level of a signed distance function, and evolved according to a motion equation in order to minimize a cost function. This function defines the objective of the segmentation problem and also includes regularization constraints. Gradient descent search is the de facto method used to solve this optimization problem. Basic gradient descent methods, however, are sensitive for local optima and often display slow convergence. Traditionally, the cost functions have been modified to avoid these problems. In this work, we instead propose using a modified gradient descent search based on resilient propagation (Rprop), a method commonly used in the machine learning community. Our results show faster convergence and less sensitivity to local optima, compared to traditional gradient descent.

  • 5. Arcella, A
    et al.
    Cavaliere, S
    Università di Napoli.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Recognition of sounds from musical instruments: a critical review and experiments2004In: Proc. of the IV Conference on Understanding and Creating Music (UCM), 2004Conference paper (Other academic)
  • 6. B Zafar, N
    et al.
    Åkesson, Johan
    Roble, D
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Scattered Spherical Harmonic Approximation for Accelerated Volume Rendering2006In: ACM SIGGRAPH ¿06 Sketches Applications,2006, 2006Conference paper (Refereed)
  • 7.
    Baravdish, George
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    A Variational Method for Image Reconstruction2008In: International Conference on Inverse Problems in Engineering: Theory and Practice ICIPE 2008,2008, 2008, p. 58:1-58:3Conference paper (Other academic)
  • 8.
    Braude, I.
    et al.
    Department of Computer Science, Drexel University, Philadelphia, PA, United States.
    Marker, J.
    Department of Computer Science, Drexel University, Philadelphia, PA, United States.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Nissanov, J.
    Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.
    Breen, D.
    Department of Computer Science, Drexel University, Philadelphia, PA, United States.
    Contour-based surface reconstruction using MPU implicit models2007In: Graphical Models, ISSN 1524-0703, E-ISSN 1524-0711, Vol. 69, no 2, p. 139-157Article in journal (Refereed)
    Abstract [en]

    This paper presents a technique for creating a smooth, closed surface from a set of 2D contours, which have been extracted from a 3D scan. The technique interprets the pixels that make up the contours as points in R3 and employs multi-level partition of unity (MPU) implicit models to create a surface that approximately fits to the 3D points. Since MPU implicit models additionally require surface normal information at each point, an algorithm that estimates normals from the contour data is also described. Contour data frequently contains noise from the scanning and delineation process. MPU implicit models provide a superior approach to the problem of contour-based surface reconstruction, especially in the presence of noise, because they are based on adaptive implicit functions that locally approximate the points within a controllable error bound. We demonstrate the effectiveness of our technique with a number of example datasets, providing images and error statistics generated from our results. © 2006 Elsevier Inc. All rights reserved.

  • 9. Breen, David
    et al.
    Fedkiw, Ron
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Osher, Stanley
    Sapiro, G
    Whitaker, Ross
    Level Sets and PDE Methods for Computer Graphics2004Other (Other (popular science, discussion, etc.))
  • 10. Breen, David
    et al.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Level Sets Methods for Visualization2006Other (Other (popular science, discussion, etc.))
  • 11. Breen, David
    et al.
    Whitaker, Ross
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Zhukov, L
    Level Set Segmentation of Biological Volume Datasets2005In: Handbook of Medical Image Analysis: Volume 3, Registration models [Elektronisk resurs] / [ed] Jasjit S. Suri, David L. Wilson and Swamy Laxminarayan, New York: Kluwer , 2005, p. 415-478Chapter in book (Other academic)
    Abstract [en]

    Handbook of Biomedical Image Analysis: Registration Models (Volume III) is dedicated to the algorithms for registration of medical images and volumes. This volume is aimed at researchers and educators in imaging sciences, radiological imaging, clinical and diagnostic imaging, biomedical engineering, physicists covering different medical imaging modalities and researchers in applied mathematics, algorithmic development, computer vision, signal processing, computer graphics and multimedia in general, both in academia and industry.

  • 12.
    Brun, Anders
    et al.
    Centre for Image Analysis, Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Ola
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Reimers, Martin
    Department of Informatics and Centre of Mathematics for Applications, University of Oslo, Norway.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Knutsson, Hans
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Computing Riemannian Normal Coordinates on Triangle MeshesManuscript (preprint) (Other academic)
    Abstract [en]

    Imagine an ant walking around on the curved surface of a plant, a radio amateur planning to broadcast to a distant location across the globe or a pilot taking o from an airport - all of them are helped by egocentric maps of the world around them that shows directions and distances to various remote places. It is not surprising that this idea has already been used in cartography, where it is known as Azimuthal Equidistant Projection (AEP). If Earth is approximated by a sphere, distances and directions between two places are computed from arcs along great circles. In physics and mathematics, the same idea is known as Riemannian Normal Coordinates (RNC). It has been given a precise and general denition for surfaces (2-D), curved spaces (3-D) and generalized to smooth manifolds (N-D). RNC are the Cartesian coordinates of vectors that index points on the surface (or manifold) through the so called exponential map, which is a well known concept in dierential geometry. They are easily computed for a particular point if the inverse of the exponential map, the logarithm map, is known. Recently, RNC and similar coordinate systems have been used in computer graphics, visualization and related areas of research. In Fig. 1 for instance, RNC are used to produce a texture on the Stanford bunny through decal compositing. Given the growing use of RNC, which is further elaborated on in the next section, it is meaningful to develop accurate and reproducible techniques to compute this parameterization. In this paper, we describe a technique to compute RNC for surfaces represented by triangular meshes, which is the predominant representation of surfaces in computer graphics. The method that we propose has similarities to the Logmap framework, which has previously been developed for dimension reduction of unorganized point clouds in high-dimensional spaces, a.k.a. manifold learning. For this reason we sometimes refer to it as "Logmap for triangular meshes" or simply Logmap.

  • 13.
    Buckwalter, Claes
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    A Messaging-Based Integration Architecture for Print Production Workflow Systems2006In: Proceedings of Printing Technology SPb’06, 2006, p. 13-17Conference paper (Refereed)
    Abstract [en]

    A print production workflow consists of a number of systems

    specialized at executing specific tasks. In order to realize an

    efficient workflow it is not enough to simply assemble all the

    required systems, the systems must also communicate with each

    other and exchange information. The printing industry has used

    several approaches for integrating systems. A common

    approach has been to use so-called “hot folders” to exchange

    content files, such as PDF documents, between systems.

    Another approach, which focuses on the exchange of production

    and configuration data, is the XML-based Job Definition

    Format (JDF) and its messaging protocol Job Messaging

    Format (JMF).

     

    The need to integrate heterogeneous systems is nothing unique

    to the printing industry. The experience and knowledge in this

    area has been documented in several pattern languages. By

    applying a combination of several such pattern languages, this

    paper presents a hypothetical integration architecture that

    enables a system to communicate with other systems using JMF

    messaging.

  • 14.
    Buckwalter, Claes
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Integrating Systems in the Print Production Workflow: Aspects of Implementing JDF2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The print production workflow consists of various disparate systems — from production equipment to management information systems. During the production of a printed product, information regarding the product must be communicated between the systems in the workflow. Job Definition Format (JDF) is an industry standard that specifies this information interchange. It specifies a digital job ticket format for exchanging administrative and technical information related to a print job, and a messaging protocol for communicating information between the systems in the workflow. This licentiate thesis explores different aspects of integrating systems in a JDF-enabled print production workflow.

    Paper III and Paper IV analyze the properties of JDF’s messaging protocol—Job Messaging Format (JMF)—and discuss design solutions for a JMF integration layer.

    Paper I presents a software tool for simulating systems in the print production workflow. The tool is based on an open source software library, called the Elk Framework, which has been developed within the framework of these licentiate studies. The Elk Framework provides the base services required by a piece of JDF-enabled production equipment, called a Device/Worker in JDF parlance.

    Paper II presents a software tool that was developed for testing the simulation tool presented in Paper I. The test tool, named Alces, can be used for testing if JDF-enabled systems conform to the JDF Specification.

    List of papers
    1. A JDF-enabled Workflow Simulation Tool
    Open this publication in new window or tab >>A JDF-enabled Workflow Simulation Tool
    2005 (English)In: Proceedings of TAGA 57th Annual Technical Conference 2005, 2005, Vol. 57, p. 271-281Conference paper, Published paper (Refereed)
    Abstract [en]

    Job Definition Format (JDF) is a relatively young industry

    standard that specifies a workflow model and a data format for

    describing print jobs and exchanging production information. Although

    most vendors today offer JDF-enabled products, little research has been

    conducted aiming at measuring the benefits of using JDF in production.

    One reason for this is likely the lack of suitable tools.

    This paper presents a JDF-compliant tool that can be used to simulate the

    interaction of arbitrary devices in a print production workflow. This tool

    has many usage scenarios, one of them being the possibility to simulate

    devices in “live” production in order to measure JDF performance and

    detect production bottlenecks.

     

    Keywords
    Job Definition Format, JDF, JMF, print production, workflow, simulation, software framework
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14163 (URN)
    Available from: 2006-12-04 Created: 2006-12-04 Last updated: 2009-05-07
    2. A Tool for Testing Compliance with CIP4’s Interoperability Conformance Specifications
    Open this publication in new window or tab >>A Tool for Testing Compliance with CIP4’s Interoperability Conformance Specifications
    2005 (English)In: Proceedings of 2005 International Conference on Digital Production Printing and Industrial Applications, 2005, p. 83-84Conference paper, Published paper (Refereed)
    Abstract [en]

    Job Definition Format (JDF) is a relatively young industry standard developed by The International Cooperation for the Integration of Processes in Prepress, Press and Postpress (CIP4). JDF specifies a data format for describing print jobs and exchanging production information between systems in the print production workflow. Most vendors in the printing industry today offer “JDF-enabled ” products, but the industry lacks a well-defined test protocol and specialized tools for testing and verifying the level of JDF-compliance that products have. This paper presents an open source test tool for testing the level of JDF compliance as specified by the CIP4 organization’s Interoperability Conformance Specification (ICS) documents. The test tool is semiautomated and validates system behavior and output of JDF instances and JMF messages both syntactically and based on context.

    Keywords
    Job Definition Format, JDF, Job Messaging Format, JMF, print production, testing
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14164 (URN)0-89208-256-9 (ISBN)
    Available from: 2006-12-04 Created: 2006-12-04 Last updated: 2009-05-07
    3. Integration Patterns Applied to Print Production
    Open this publication in new window or tab >>Integration Patterns Applied to Print Production
    2006 (English)In: Proceedings of TAGA 58th Annual Technical Conference 2006, 2006, Vol. 58, p. 54-68Conference paper, Published paper (Refereed)
    Abstract [en]

    In a modern printing plant software systems are ubiquitous and indispensable. Systems for order management, production planning, and other administrative systems are implemented in software. Most, if not all, equipment on the plant floor has a software front-end that either controls the physical equipment directly or displays instructions for a human operator to interpret and execute. These software systems are not isolated islands. During production they need to communicate and exchange information. For example, a prepress workflow system may send configuration parameters to production equipment and production equipment may send status updates to production monitoring systems. This type of communication is typically implemented by sending messages, discrete units of data, between the systems. Integrating heterogeneous systems using messaging is nothing unique to the printing industry. It is a well-proven solution and there are several general-purpose solutions available for integrating disparate systems using messaging. The experience and knowledge on the subject has been documented in several pattern languages. This paper examines Job Definition Format’s messaging protocol Job Messaging Format (JMF), and maps JMF concepts to patterns found in pattern languages for system integration using messaging. Weaknesses found in JMF are discussed and patterns are applied to suggest alternative solutions. The result is JMF expressed using general enterprise integration patterns.

    Keywords
    messaging, integration, pattern language, JMF, JDF
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14165 (URN)
    Available from: 2006-12-04 Created: 2006-12-04 Last updated: 2009-02-17
    4. A Messaging-Based Integration Architecture for Print Production Workflow Systems
    Open this publication in new window or tab >>A Messaging-Based Integration Architecture for Print Production Workflow Systems
    2006 (English)In: Proceedings of Printing Technology SPb’06, 2006, p. 13-17Conference paper, Published paper (Refereed)
    Abstract [en]

    A print production workflow consists of a number of systems

    specialized at executing specific tasks. In order to realize an

    efficient workflow it is not enough to simply assemble all the

    required systems, the systems must also communicate with each

    other and exchange information. The printing industry has used

    several approaches for integrating systems. A common

    approach has been to use so-called “hot folders” to exchange

    content files, such as PDF documents, between systems.

    Another approach, which focuses on the exchange of production

    and configuration data, is the XML-based Job Definition

    Format (JDF) and its messaging protocol Job Messaging

    Format (JMF).

     

    The need to integrate heterogeneous systems is nothing unique

    to the printing industry. The experience and knowledge in this

    area has been documented in several pattern languages. By

    applying a combination of several such pattern languages, this

    paper presents a hypothetical integration architecture that

    enables a system to communicate with other systems using JMF

    messaging.

    Keywords
    jdf, jmf, print, workflow, integration, messaging
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14166 (URN)
    Available from: 2006-12-04 Created: 2006-12-04 Last updated: 2009-05-07
  • 15.
    Bui, Hai Thanh
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lenz, Reiner
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Color and texture induced structures of keyword space2005In: Proceedings of the 10th Congress of the International Colour Association,2005, Granada: International Colour Association , 2005, p. 1059-Conference paper (Refereed)
  • 16.
    Bui, Hai Thanh
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Landelius, Tomas
    SMHI.
    Group theoretical investigations of daylight spectra2004In: 2nd European Conference on Color in Graphics, Imaging and Vision,2004, Springfield, VA, USA: IST: The Society for Imaging Science and Technology , 2004, p. 437-Conference paper (Refereed)
  • 17.
    Bui, Hai Thanh
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Lenz, Reiner
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Solli, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Illumination Induced Changes in Image Statistics2006In: CGIV 2006, Third European Conference on Color in Graphics, Imaging and Vision, 7003 Kilworth Lane, Springfield, VA 22151 USA: The Society for Imaging Science and Technology , 2006, , p. 48-53p. 48-53Conference paper (Refereed)
    Abstract [en]

    We have previously shown that it is possible to construct a coordinate system in the space of illumination spectra such that the coordinate vectors of the illuminants are located in a cone. Changes in the space of illuminants can then be described by an intensity related scaling and a transformation in the Lorentz group SU(1,1). In practice it is often difficult and expensive to measure these coordinate vectors. Therefore it is of interest to estimate the characteristics of an illuminant from an RGB image captured by a camera. In this paper we will investigate the relation between sequences of illuminants and statistics computed from RGB images of scenes illuminated by these illuminants. As a typical example we will study sequences of black body radiators of varying temperature. We have shown earlier that black body radiators in the mired parametrization can be described by one-parameter groups of the Lorentz group SU(1,1). In this paper we will show that this group theoretical structure of the illuminant space induces a similar structure in spaces of statistical descriptors of the resulting RGB images. We show this relation for mean vectors of RGB images, for RGB histograms and for histograms of images obtained by applying certain spatiospectral linear filters to the RGB images. As a result we obtain estimates of the color temperature of the illuminant from sequences of RGB images of scenes under these illuminants.

  • 18.
    Bui, Hai Thanh
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Takase, Koichi
    Chiba University.
    Fast low-level filter systems for multispectral color images2005In: proceedings of the 10th Congress of the International Colour Association,2005, Granada: International Colour Association , 2005, p. 535-Conference paper (Refereed)
  • 19.
    Carmona, Pedro Latorre
    et al.
    Depto. Lenguajes y Sistemas Informáticos, Universidad Jaume I, Castellón de la Plana, Spain.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Performance evaluation of dimensionality reduction techniques for multispectral images2007In: International journal of imaging systems and technology (Print), ISSN 0899-9457, E-ISSN 1098-1098, Vol. 17, no 3, p. 202-217Article in journal (Refereed)
    Abstract [en]

    We consider several collections of multispectral color signals and describe how linear and non-linear methods can be used to investigate their internal structure. We use databases consisting of blackbody radiators, approximated and measured daylight spectra, multispectral images of indoor and outdoor scenes under different illumination conditions and numerically computed color signals. We apply Principal Components Analysis, group-theoretical methods and three manifold learning methods: Laplacian Eigenmaps, ISOMAP and Conformal Component Analysis. Identification of low-dimensional structures in these databases is important for analysis, model building and compression and we compare the results obtained by applying the algorithms to the different databases.

  • 20.
    Chao, Jinhui
    et al.
    Chuo University.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Matsumoto, Daisuke
    Nakamura, Tatsuya
    Riemann Geometry for Color Characterization and Mapping2008In: Proc. CGIV 2008, 7003 Kilworth Lane, Springfield, VA 22151 USA: Society for Imaging Science and Technology , 2008, , p. 277-282p. 277-282Conference paper (Refereed)
    Abstract [en]

    In this paper, we use Riemann geometry to develop a generalframework for the characterization of and mapping betweencolor spaces. Within this framework we show how to constructmaps, so-called isometries, between two color spaces that preservecolor differences. We illustrate applications of this frameworkby constructing a uniform color space and developing algorithmsfor color reproduction on different printers and correctionof color-vision for color-weak observers.

  • 21.
    Cortat, Frédéric
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Application of the variational calculus to wetting phenomena in chemical engineering2004Report (Other academic)
  • 22.
    Cortat, Frédéric
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    How closely can a solid approach an air-water surface without becoming wet?2003In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 68, no 5Article in journal (Refereed)
    Abstract [en]

    Through a study of the van der Waals interaction between a solid and an air-water interface, we investigate the practical and fundamental problem of the limiting height at which an object can approach a free surface. A numerical study of the interface shape reveals dependencies governed by two disparate length scales associated with the relative strengths of the van der Waals and bouyancy forces, to surface tension. A study of the limits of solvability of the governing equation has led to the principal result: a closed-form expression for the absolute limiting height to which an object can be lowered to the air-water interface. The formula depends explicitly and only on the Hamaker constant of the van der Waals force and the geometry of the solid.

  • 23.
    Cortat, Frédéric
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Miklavcic, Stan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Using stable and unstable profiles to deduce deformation limits of the air-water interface2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 8, p. 3208-3220Article in journal (Refereed)
    Abstract [en]

    The shape of the air-water interface deformed by a van der Waals stress induced by a paraboloid shaped solid body is addressed and discussed. Emphasis is placed on the existence limit of solutions to the governing Euler-Lagrange equation for the equilibrium shape. Two legitimate solutions, one stable and one unstable, are found to converge at the existence limit, giving a numerical criterion for establishing critical physical conditions guaranteeing absolute stability. Insight is aided by a study of an analogous mechanical problem that exhibits very similar properties. Among numerical data produced are critical lower height limits of the paraboloid to the air-water surface and associated peak deformation heights and their dependencies on physical parameters. Of further interest to experimentalists in the surface force field are the variations in peak deformation height and total surface force on the solid as a function of position of the paraboloid, paraboloid geometry, and strength of the van der Waals stress.

  • 24.
    Eckerholm, Fredrik
    et al.
    Audio Sony-Ericsson.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    The PluckSynth touch string2008In: Proc. of Digital Audio Effects Conf. (DAFx `08), Helsinki, Finland: DAFx , 2008, p. 213-220Conference paper (Refereed)
    Abstract [en]

    In this paper the problem of the synthesis of plucked strings by means of physically inspired models is reconsidered in the context of the player-s interaction with the virtual instrument. While solutions for the synthesis of guitar tones have been proposed, which are excellent from the acoustic point of view, the problem of the control of the physical parameters directly by the player has not received sufficient attention. In this paper we revive a simple model previously presented by Cuzzucoli and Lombardo for the player-s touch. We show that the model is affected by an inconsistency that can be removed by introducing the finger/pick perturbation in a balanced form on the digital waveguide. The results, together with a more comprehensive model of the guitar have been implemented in a VST plugin, which is the starting point for further research.

  • 25.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Fractal Modulation Effects2013In: Proc. of Digital Audio Effects Conference (DAFx `06), Montreal, Canada: DAFx , 2013, p. 101-106Conference paper (Refereed)
    Abstract [en]

    Fractal modulation is obtained by forming a power weighted superposition of scaled and modulated versions of the signal. The resulting signal is self-similar with fractal characteristics. In this paper we explore fractal modulation as a powerful method to generate rich signals, useful both for the synthesis of complex sounds, like the sounds from natural events or ecological sounds, or as control functions of audio effects. The wavelet transform can be used as an efficient tool in order to generate a subset of fractal modulated signals that are power homogeneous. Any signal used as a seed for fractal modulation is transformed into a multiscale sound by means of a tree-structured multirate filter bank. Moreover, by superimposing a structured modulation scheme one can generate pseudo-periodic sounds whose partials have fractal behavior.

  • 26.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Modified phase vocoder scheme for dynamic frequency warping2008In: 3rd International Symposium on Communications, Control and Signal Processing, 2008. ISCCSP 2008., Piscataway, NJ, USA: IEEE , 2008, p. 1291-1296Conference paper (Refereed)
    Abstract [en]

    Frequency warping is a desirable building block for sound effects and synthesis. Physical model driven pitch shifting of inharmonic sounds and the transformation of harmonic into inharmonic sounds are the main features of frequency warping effects. However, frequency warping sound signals is a non-causal and computationally expensive operation. In recent work [1] we showed that multirate filter bank s derived from a modified phase vocoder structure are suitable for the real-time approximate computation of frequency warping. The approximation is proven to be very accurate from both numerical and perceptual points of view. In this paper we extend the principles of the original design to implement time-varying frequency warping methods. The proposed algorithm is suitable for inclusion in the synthesis of systems with dynamic stiffness and for the production of captivating audio effects.

  • 27.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Cavaliere, Sergio
    Univ. of Naples, Italy.
    Event Synchronous Thumbnails: Experiments2005In: Proc. of Sound and Music Computing Conf. (SMCᅵ05), 2005Conference paper (Other academic)
  • 28.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Cavaliere, Sergio
    Dept. Physical Sciences Federico II of Naples, Italy.
    Real-Time and Efficient Algorithms for Frequency Warping Based on Local Approximations of Warping Operators2007In: Proc. of Digital Audio Effects Conf. (DAFx `07), France: DAFx , 2007, p. 269-276Conference paper (Refereed)
    Abstract [en]

    Frequency warping is a modifier that acts on sound signals by remapping the frequency axis. Thus, the spectral content of the original sound is displaced to other frequencies. At the same time, the phase relationship among the signal components is altered, nonlinearly with respect to frequency. While this effect is interesting and has several applications, including in the synthesis by physical models, its use has been so far limited by the lack of an accurate and flexible real-time algorithm. In this paper we present methods for frequency warping that are based on local approximations of the warping operators and allow for real-time implementation. Filter bank structures are derived that allow for efficient realization of the approximate technique. An analysis of the error is also presented, which shows that both numerical and perceptual errors are within acceptable limits. Furthermore, the approximate implementation allows for a larger variety of warping maps than that achieved by the classical (non-causal) first-order allpass cascade implementation.

  • 29.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Cavaliere, Sergio
    Univ. of Naples, Italy.
    Tontodonato, Valentino
    Event Synchronous Thumbnails: Statistical Properties2005In: Proc. of the V Conference on Understanding and Creating Music (UCM), 2005Conference paper (Other academic)
  • 30.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Polotti, Pietro
    VIPS University of Verona, Italy.
    Fractal Additive Synthesis: a Deterministic/Stochastic Model for Sound Synthesis by Analysis2007In: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 24, no 2, p. 105-115Article in journal (Refereed)
  • 31.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Raspaud, Martin
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Simplified Guitar Bridge Model for the Displacement Wave Representation in Digital Waveguides2009In: Proceedings of the 12th International Conference on Digital Audio Effects, DAFx 2009, 2009, p. 484-491Conference paper (Other academic)
  • 32.
    Germain, François
    et al.
    Ecole Polytechnique.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Synthesis of Guitar by Digital Waveguides: Modeling the Plectrum in the Physical Interaction of the Player with the Instrument2009In: Proc. of the IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA-09), 2009, p. 25-28Conference paper (Other academic)
    Abstract [en]

    In this paper, we provide a model of the plectrum, or guitar pick, for use in physically inspired sound synthesis. The model draws from the mechanics of beams. The profile of the plectrum is computed in real time based on its interaction with the string, which depends on the movement impressed by the player and the equilibrium of dynamical forces. A condition for the release of the string is derived, which allows to drive the digital waveguide simulating the string to the proper state at release time. The acoustic results are excellent, as verified in the sound examples provided.

  • 33.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    A Novel Hybrid AM/FM Halftoning Based on Multi-level Halftoning2006In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 50, no 2, p. 157-167Article in journal (Refereed)
    Abstract [en]

    A digital gray scale image generally consists of 256 different gray tones. Printers and image setters normally generate much fewer levels and mostly only two levels. Therefore, in order to be able to display a digital cone-tone image by a multilevel device it has to be transformed into an image with fewer levels. The technique doing this transformation is called multi-level halftoning, and in the case of bilevel devices it is simply called halftoning. In this paper we propose a novel (bilevel) halftoning technique that is based on multilevel halftoning. The proposed method can also be categorized as belonging to hybrid amplitude modulated (AM)/ frequency modulated (FM) techniques. In this method the original digital image is firstly halftoned by a multilevel FM halftoning. Each level in the multilevel halftoned image is then replaced by a halftone table (microcell). An approach for extending any bilevel FM halftoning method to a multilevel method is also presented in this paper. The performance of the proposed method is examined by a number of illustrations where nonmodified error diffusion and our FM method are used. The problem with maze-like artifacts that occur when our FM halftoning, or similar methods such as DBS, are used as the macroscreen is discussed and a simple solution is introduced. An approach for extending the proposed method to be used in situations where the halftone dots cannot be produced smaller than a specific size is also proposed and examined. This modified version of the method can be useful for flexography, where the dots normally cannot be produced smaller than a critical size.

  • 34.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Dependent color halftoning: Better quality with less ink2004In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 48, no 4, p. 354-362Article in journal (Refereed)
    Abstract [en]

    When a color image is halftoned its color channels are normally halftoned independently. The dots in different channels are placed independent of each other and consequently the final result may not be of high quality even if a. well performing monochromatic halftoning method has been used. In this article we propose a method that halftones the channels of the color image in a context dependent manner. Since the yellow ink on a white paper is hardly visible, only cyan and magenta separations need to be halftoned dependently. We also show that dependent color halftoning not only increases the halftone image quality but also decreases the amount of ink needed to reproduce different colors.

  • 35.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Hybrid halftoning, a useful method for flexography2005In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 49, no 1, p. 85-95Article in journal (Refereed)
    Abstract [en]

    Most printing devices, such as laser and ink jet printers and many print presses, are restricted to very few colors. The contone images should therefore be transformed into binary ones before being printed. The techniques doing this transformation are referred to as halftoning methods. Halftoning methods can be divided into two main categories, namely AM (Amplitude Modulated) and FM (Frequency Modulated). Some printing methods, such as Flexography, are not able to produce dots sufficiently small in order to handle the highlights and the shadows of the original image by using just an AM halftoning method. In this article we propose a hybrid halftoning method that incorporates AM and FM technologies in order to overcome this problem. The strategy is to use an FM method in the highlights (and the shadows) of the image and an AM method in the rest of the image.

  • 36.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    In Dependent Color Halftoning, Yellow Matters2006In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 50, no 5, p. 448-457Article in journal (Refereed)
  • 37.
    Gooran, Sasan
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Optical Dot Gain and Color Halftoning with Three Different Printing Strategies: Independent2008In: Technical Association of the Graphic Arts TAGA,2008, 2008Conference paper (Refereed)
    Abstract [en]

      

  • 38.
    Gooran, Sasan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Kruse, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    A novel bi-level halftoning technique based on multi-level halftoning2005In: Proceedings of the Beijing Internaltional Conference on Imaging 2005,2005, New York, US: Science Press , 2005, p. 122-Conference paper (Refereed)
  • 39.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Hybrid halftoning2004Report (Other academic)
  • 40.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Namedanian, Mahziar
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    A New Approach to Calculate Colour Values of Halftone Prints2009Conference paper (Other academic)
    Abstract [en]

    Printed dots appear bigger than their reference size in the original bitmap. This is because of the physical and optical dot gain. In order to overcome the problem original images are compensated for dot gain. The compensation is usually done by using a dot gain curve for each colour separation. In this paper we firstly show that using only one dot gain curve works well for black, but not for any of the other three colours, i.e. cyan, magenta or yellow. We also present a new approach to calculate colour values where three different curves are used for each colour separation. In order to evaluate the proposed approach we compare the results of our method with the results when only one dot gain curve is used for each colour, both for Murray-Davies and Yule-Nielsen models. In the case of only one dot gain curve for each separation we use the curve that gives a minimized ∆ELab using least squares method. The experiments and calculations show that our approach gives a better approximation of the resulting colour coordinates.

  • 41. Gómez, G
    et al.
    Lo, M
    Masdemont, J
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Simulation of Formation Flight Near Lagrange Points for the TPF Mission2001In: American Astronautical Society AAS/AIAA, Astrodynamics Specialist Conference,2001, 2001, p. 305-Conference paper (Refereed)
  • 42.
    Heikkinen, Ville
    et al.
    University of Joensuu.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Jetsu, Tuija
    University of Joensuu.
    Parkkinen, Jussi
    University of Joensuu.
    Hauta-Kasari, Markku
    University of Joensuu.
    Jaaskelainen, Timo
    University of Joensuu.
    Evaluation and unification of some methods for estimating reflectance spectra from RGB images2008In: Journal of the Optical Society of America. A, Optics, image science and vision, ISSN 1084-7529, Vol. 25, no 10, p. 2444-2458Article in journal (Refereed)
    Abstract [en]

    The problem of estimating spectral reflectances from the responses of a digital camera has received considerable attention recently This problem can be cast as a regularized regression problem or as a statistical inversion problem. We discuss some previously suggested estimation methods based on critically undersampled RGB measurements and describe some relations between them. We concentrate mainly on those models that are using a priori information in the form of high-resolution measurements. We use the "kernel machine" framework in our evaluations and concentrate on the use of multiple illuminations and on the investigation of the performance of global and locally adapted estimation methods. We also introduce a nonlinear transformation of reflectance values to ensure that the estimated reflection spectra fulfill physically motivated boundary conditions. The reported experimental results are derived from measured and simulated camera responses from the Mansell Matte, NCS, and Pantone data sets.

  • 43.
    Heikkinen, Ville
    et al.
    University of Joensuu Finland.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Jetsu, Tuija
    University of Joensuu Finland.
    Parkkinen, Jussi
    University of Joensuu Finland.
    Jääskeläinen, Timo
    University of Joensuu Finland.
    Estimation of Reflectance Spectra Using Multiple Illuminations2008In: Proc. CGIV 2008, 7003 Kilworth Lane, Springfield, VA 22151 USA: Society for Imaging Science and Technology , 2008, , p. 272-276p. 272-276Conference paper (Refereed)
    Abstract [en]

    Using ordinary digital cameras as relatively cheap measurementdevices for estimating spectral color properties has becomean interesting alternative to making pointwise high precisionspectral measurements with special equipments like photospectrometers.The results obtained with these methods cannotcompete with the quality of the traditional high resolutiondevices but they are very attractive since the equipment is relativelycheap and instant measurements are obtained for millionsof measurement points.In this paper we investigate the problem of estimating reflectancespectra from measurements taken with ordinary digitalRGB cameras. We study the effects of using multiple illuminationsand treat the estimation of the reflectance spectra asa regression or a statistical inversion problem. We use both,linear- and non-linear estimation methods where we focus onusing reproducing kernels to avoid explicit formulation of nonlinearities.We also include non-linear conditions based on theproperties of the reflection spectra. Munsell Matte color andPantone are used as data sets to support the proposed methods.The experiments show that the proposed methods improve the estimationresults when compared to standard linear methods.

  • 44. Houston, B
    et al.
    Bang Nielsen, Michael
    Batty, C
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Gigantic Deformable Surfaces2005In: ACM SIGGRAPH 05, Sketches Applications,2005, 2005Conference paper (Refereed)
  • 45.
    Houston, Ben
    et al.
    Exocortex Technologies, Frantic Films.
    Nielson, Michael B.
    University of Århus.
    Batty, Christopher
    University of British Columbia, Frantic Films.
    Nilsson, Ola
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Hierarchical RLE level set: A compact and versatile deformable surface representation2006In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 25, no 1, p. 151-175Article in journal (Refereed)
    Abstract [en]

    This article introduces the Hierarchical Run-Length Encoded (H-RLE) Level Set data structure. This novel data structure combines the best features of the DT-Grid ( of Nielsen and Museth [ 2004]) and the RLE Sparse Level Set ( of Houston et al. [ 2004]) to provide both optimal efficiency and extreme versatility. In brief, the H- RLE level set employs an RLE in a dimensionally recursive fashion. The RLE scheme allows the compact storage of sequential nonnarrowband regions while the dimensionally recursive encoding along each axis efficiently compacts nonnarrowband planes and volumes. Consequently, this new structure can store and process level sets with effective voxel resolutions exceeding 5000 x 3000 x 3000 ( 45 billion voxels) on commodity PCs with only 1 GB of memory. This article, besides introducing the H- RLE level set data structure and its efficient core algorithms, also describes numerous applications that have benefited from our use of this structure: our unified implicit object representation, efficient and robust mesh to level set conversion, rapid ray tracing, level set metamorphosis, collision detection, and fully sparse fluid simulation ( including RLE vector and matrix representations.) Our comparisons of the popular octree level set and Peng level set structures to the H- RLE level set indicate that the latter is superior in both narrowband sequential access speed and overall memory usage.

  • 46.
    Johansson, Gunnar
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Digital Media.
    Nilsson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Söderström, Andreas
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Distributed Ray Tracing in an Open Source Environment (Work in Progress)2006Conference paper (Refereed)
    Abstract [en]

    We present work in progress on concurrent ray tracing with distributed computers using ``off-the-shelf'' open source software. While there exists numerous open source ray tracers, very few offer support for state-of-the-art concurrent computing. However, it is a well known fact that ray tracing is computationally intensive and yet prevails as the preferred algorithm for photorealistic rendering. Thus, the current work is driven by a desire for a simple programming strategy (or recipe) that allows pre-existing ray tracing code to be parallelized on a heterogenous cluster of available office computers - strictly using open source components. Simplicity, stability, efficiency and modularity are the driving forces for this engineering project, and as such we do not claim any novel research contributions. However, we stress that this project grew out of a real-world need for a render cluster in our research group, and consequently our solutions have a significant practical value. In fact some of our results show a close to optimal speedup when considering the relative performances of each node. In this systems paper we aim at sharing these solutions and experiences with other members of the graphics community.

  • 47.
    Johansson, Linda
    et al.
    Linköping University, Department of Science and Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    A Colour Separation Strategy for Reproduction of Printed Dynamic Images on Paper Substrate2005In: iarigai Research Conference,2005, Zagreb: Iarigai , 2005, p. 191-Conference paper (Refereed)
  • 48.
    Johansson, Linda
    et al.
    Linköping University, Department of Science and Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    The Influence of Paper Properties on Colour Reproduction with Dynamic Inks2005In: 2005 Beijing International Conference on Imaging: Technology and Applications for the 21st Century,2005, 2005, p. 214-215Conference paper (Other academic)
  • 49.
    Johansson Läthén, Gunnar
    et al.
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Carr, Hamish
    School of Computer Science and Informatics, University College Dublin.
    Flexible and Topologically Localized Segmentation2007In: EuroVis07 Joint Eurographics: IEEE VGTC Symposium on Visualization / [ed] Ken Museth, Torsten Möller, and Anders Ynnerman, Aire-la-Ville, Switzerland: Eurographics Association , 2007, , p. 179-186p. 179-186Conference paper (Refereed)
    Abstract [en]

    One of the most common visualization tasks is the extraction of significant boundaries, often performed with iso- surfaces or level set segmentation. Isosurface extraction is simple and can be guided by geometric and topological analysis, yet frequently does not extract the desired boundary. Level set segmentation is better at boundary extrac- tion, but either leads to global segmentation without edges, [CV01], that scales unfavorably in 3D or requires an initial estimate of the boundary from which to locally solve segmentation with edges. We propose a hybrid system in which topological analysis is used for semi-automatic initialization of a level set segmentation, and geometric information bounded topologically is used to guide and accelerate an iterative segmentation algorithm that com- bines several state-of-the-art level set terms. We thus combine and improve both the flexible isosurface interface and level set segmentation without edges.

  • 50. Kirby, M
    et al.
    Lefohn, A
    Museth, Ken
    Linköping University, Department of Science and Technology, Digital Media. Linköping University, The Institute of Technology.
    Preusser, T
    Sapiro, G
    Whitaker, Ross
    Level Set and PDE Methods for Visualization2005Other (Other (popular science, discussion, etc.))
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