Publications about Active contour

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• 5 Articles
• 2 PhD Thesis and Habilitations
• 10 Conference articles
• 5 Technical and Research Reports

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10 Conference articles

4 - Urban road extraction from VHR images using a multiscale image model and a phase field model of network geometry. T. Peng and I. H. Jermyn and V. Prinet and J. Zerubia. In Proc. Urban, Paris, France, April 2007. Keywords : Road network, Very high resolution, Multiscale, Higher-order, Active contour, Shape. @INPROCEEDINGS{Peng07_urban, author = {Peng, T. and Jermyn, I. H. and Prinet, V. and Zerubia, J.}, title = {Urban road extraction from VHR images using a multiscale image model and a phase field model of network geometry}, year = {2007}, month = {April}, booktitle = {Proc. Urban}, address = {Paris, France}, pdf = {http://www-sop.inria.fr/members/Ian.Jermyn/publications/Peng07urban.pdf}, keyword = {Road network, Very high resolution, Multiscale, Higher-order, Active contour, Shape} } Abstract : This paper addresses the problem of automatically extracting the main road network in a dense urban area from a very high resolution optical satellite image using a variational approach. The model energy has two parts: a phase field higherorder active contour energy that describes our prior knowledge of road network geometry, i.e. that it is composed of elongated structures with roughly parallel borders that meet at junctions; and a multi-scale statistical image model describing the image we expect to see given a road network. By minimizing the model energy, an estimate of the road network is obtained. Promising results on 0.6m QuickBird Panchromatic images are presented, and future improvements to the models are outlined.

5 - An improved 'gas of circles' higher-order active contour model and its application to tree crown extraction. P. Horvath and I. H. Jermyn and Z. Kato and J. Zerubia. In Proc. Indian Conference on Computer Vision, Graphics, and Image Processing (ICVGIP), Madurai, India, December 2006. Keywords : Tree Crown Extraction, Aerial images, Higher-order, Active contour, Gas of circles, Shape. @INPROCEEDINGS{Horvath06_icvgip, author = {Horvath, P. and Jermyn, I. H. and Kato, Z. and Zerubia, J.}, title = {An improved 'gas of circles' higher-order active contour model and its application to tree crown extraction}, year = {2006}, month = {December}, booktitle = {Proc. Indian Conference on Computer Vision, Graphics, and Image Processing (ICVGIP)}, address = {Madurai, India}, url = {http://dx.doi.org/10.1007/11949619_14}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/2006_Horvath06_icvgip.pdf}, keyword = {Tree Crown Extraction, Aerial images, Higher-order, Active contour, Gas of circles, Shape} } Abstract : A central task in image processing is to find the region in the image corresponding to an entity. In a number of problems, the region takes the form of a collection of circles, eg tree crowns in remote sensing imagery; cells in biological and medical imagery. In~citeHorvath06b, a model of such regions, the `gas of circles' model, was developed based on higher-order active contours, a recently developed framework for the inclusion of prior knowledge in active contour energies. However, the model suffers from a defect. In~citeHorvath06b, the model parameters were adjusted so that the circles were local energy minima. Gradient descent can become stuck in these minima, producing phantom circles even with no supporting data. We solve this problem by calculating, via a Taylor expansion of the energy, parameter values that make circles into energy inflection points rather than minima. As a bonus, the constraint halves the number of model parameters, and severely constrains one of the two that remain, a major advantage for an energy-based model. We use the model for tree crown extraction from aerial images. Experiments show that despite the lack of parametric freedom, the new model performs better than the old, and much better than a classical active contour.

6 - A Higher-Order Active Contour Model for Tree Detection. P. Horvath and I. H. Jermyn and Z. Kato and J. Zerubia. In Proc. International Conference on Pattern Recognition (ICPR), Hong Kong, August 2006. Keywords : Active contour, Gas of circles, Higher-order, Shape, Prior, Tree Crown Extraction. @INPROCEEDINGS{horvath_icpr06, author = {Horvath, P. and Jermyn, I. H. and Kato, Z. and Zerubia, J.}, title = {A Higher-Order Active Contour Model for Tree Detection}, year = {2006}, month = {August}, booktitle = {Proc. International Conference on Pattern Recognition (ICPR)}, address = {Hong Kong}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/2006_horvath_icpr06.pdf}, keyword = {Active contour, Gas of circles, Higher-order, Shape, Prior, Tree Crown Extraction} } Abstract : We present a model of a ‘gas of circles’, the ensemble of regions in the image domain consisting of an unknown number of circles with approximately fixed radius and short range repulsive interactions, and apply it to the extraction of tree crowns from aerial images. The method uses the re- cently introduced ‘higher order active contours’ (HOACs), which incorporate long-range interactions between contour points, and thereby include prior geometric information without using a template shape. This makes them ideal when looking for multiple instances of an entity in an image. We study an existing HOAC model for networks, and show via a stability calculation that circles stable to perturbations are possible for constrained parameter sets. Combining this prior energy with a data term, we show results on aerial imagery that demonstrate the effectiveness of the method and the need for prior geometric knowledge. The model has many other potential applications.

7 - Phase field models and higher-order active contours. M. Rochery and I. H. Jermyn and J. Zerubia. In Proc. IEEE International Conference on Computer Vision (ICCV), Beijing, China, October 2005. Keywords : Active contour, Higher-order, Shape, Line networks, Road network, Phase Field. @INPROCEEDINGS{rochery_iccv05, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {Phase field models and higher-order active contours}, year = {2005}, month = {October}, booktitle = {Proc. IEEE International Conference on Computer Vision (ICCV)}, address = {Beijing, China}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/rochery_iccv05.pdf}, keyword = {Active contour, Higher-order, Shape, Line networks, Road network, Phase Field} } Abstract : The representation and modelling of regions is an important topic in computer vision. In this paper, we represent a region via a level set of a `phase field' function. The function is not constrained, eg to be a distance function; nevertheless, phase field energies equivalent to classical active contour energies can be defined. They represent an advantageous alternative to other methods: a linear representation space; ease of implementation (a PDE with no reinitialization); neutral initialization; greater topological freedom. We extend the basic phase field model with terms that reproduce `higher-order active contour' energies, a powerful way of including prior geometric knowledge in the active contour framework via nonlocal interactions between contour points. In addition to the above advantages, the phase field greatly simplifies the analysis and implementation of the higher-order terms. We define a phase field model that favours regions composed of thin arms meeting at junctions, combine this with image terms, and apply the model to the extraction of line networks from remote sensing images.

8 - New Higher-order Active Contour Energies for Network Extraction. M. Rochery and I. H. Jermyn and J. Zerubia. In Proc. IEEE International Conference on Image Processing (ICIP), Genoa, Italy, September 2005. Keywords : Gap closure, Shape, Prior, Higher-order, Active contour. @INPROCEEDINGS{rochery_icip05, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {New Higher-order Active Contour Energies for Network Extraction}, year = {2005}, month = {September}, booktitle = {Proc. IEEE International Conference on Image Processing (ICIP)}, address = {Genoa, Italy}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/rochery_icip05.pdf}, keyword = {Gap closure, Shape, Prior, Higher-order, Active contour} } Abstract : Using the framework of higher-order active contours, we present a new quadratic em continuation energy for the extraction of line networks (e.g. road, hydrographic, vascular) in the presence of occlusions. Occlusions create gaps in the data that frequently translate to gaps in the extracted network. The new energy penalizes earby opposing extremities of the network, and thus favours the closure of the gaps created by occlusions. Nearby opposing extremities are identified using a sophisticated interaction between pairs of points on the contour. This new model allows the extraction of fully connected networks, even though occlusions violate common assumptions about the homogeneity of the interior, and high contrast with the exterior, of the network. We present experimental results on real aerial images that demonstrate the effectiveness of the new model for network extraction tasks.

9 - Gap closure in (road) networks using higher-order active contours. M. Rochery and I. H. Jermyn and J. Zerubia. In Proc. IEEE International Conference on Image Processing (ICIP), Singapore, October 2004. Keywords : Active contour, Gap closure, Higher-order, Shape, Road network. @INPROCEEDINGS{Rochery04, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {Gap closure in (road) networks using higher-order active contours}, year = {2004}, month = {October}, booktitle = {Proc. IEEE International Conference on Image Processing (ICIP)}, address = {Singapore}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/rochery_icip04.pdf}, keyword = {Active contour, Gap closure, Higher-order, Shape, Road network} } Abstract : We present a new model for the extraction of networks from images in the presence of occlusions. Such occlusions cause gaps in the extracted network that need to be closed. Using higher-order active contours, which allow the incorporation of sophisticated geometric information, we introduce a new, non-local, `gap closure' force that causes pairs of network extremities that are close together to extend towards one another and join, thus closing the gap between them. We demonstrate the benefits of the model using the problem of road network extraction, presenting results on aerial images.

10 - Higher Order Active Contours and their Application to the Detection of Line Networks in Satellite Imagery. M. Rochery and I. H. Jermyn and J. Zerubia. In Proc. IEEE Workshop Variational, Geometric and Level Set Methods in Computer Vision, at ICCV, Nice, France, October 2003. Keywords : Higher-order, Active contour, Shape, Road network, Segmentation, Prior. @INPROCEEDINGS{Rochery03a, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {Higher Order Active Contours and their Application to the Detection of Line Networks in Satellite Imagery}, year = {2003}, month = {October}, booktitle = {Proc. IEEE Workshop Variational, Geometric and Level Set Methods in Computer Vision}, address = {at ICCV, Nice, France}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/rochery_vlsm03.pdf}, keyword = {Higher-order, Active contour, Shape, Road network, Segmentation, Prior} } Abstract : We present a novel method for the incorporation of shape information into active contour models, and apply it to the extraction of line networks (e.g. road, water) from satellite imagery. The method is based on a new class of contour energies. These energies are quadratic on the space of one-chains in the image, as opposed to classical energies, which are linear. They can be expressed as double integrals on the contour, and thus incorporate non-trivial interactions between different contour points. The new energies describe families of contours that share complex geometric properties, without making reference to any particular shape. Networks fall into such a family, and to model them we make a particular choice of quadratic energy whose minima are reticulated. To optimize the energies, we use a level set approach. The forces derived from the new energies are non-local however, thus necessitating an extension of standard level set methods. Promising experimental results are obtained using real images.

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5 Technical and Research Reports

1 - A higher-order active contour model of a `gas of circles' and its application to tree crown extraction. P. Horvath and I. H. Jermyn and Z. Kato and J. Zerubia. Research Report 6026, INRIA, France, November 2006. Keywords : Tree Crown Extraction, Aerial images, Higher-order, Active contour, Gas of circles, Shape. @TECHREPORT{Horvath05, author = {Horvath, P. and Jermyn, I. H. and Kato, Z. and Zerubia, J.}, title = {A higher-order active contour model of a `gas of circles' and its application to tree crown extraction}, year = {2006}, month = {November}, institution = {INRIA}, type = {Research Report}, number = {6026}, address = {France}, url = {http://hal.inria.fr/inria-00115631}, pdf = {ftp://ftp-sop.inria.fr/ariana/Articles/2006_Horvath05.pdf}, keyword = {Tree Crown Extraction, Aerial images, Higher-order, Active contour, Gas of circles, Shape} } Abstract : Many image processing problems involve identifying the region in the image domain occupied by a given entity in the scene. Automatic solution of these problems requires models that incorporate significant prior knowledge about the shape of the region. Many methods for including such knowledge run into difficulties when the topology of the region is unknown a priori, for example when the entity is composed of an unknown number of similar objects. Higher-order active contours (HOACs) represent one method for the modelling of non-trivial prior knowledge about shape without necessarily constraining region topology, via the inclusion of non-local interactions between region boundary points in the energy defining the model. The case of an unknown number of circular objects arises in a number of domains, \eg medical, biological, nanotechnological, and remote sensing imagery. Regions composed of an a priori unknown number of circles may be referred to as a `gas of circles'. In this report, we present a HOAC model of a `gas of circles'. In order to guarantee stable circles, we conduct a stability analysis via a functional Taylor expansion of the HOAC energy around a circular shape. This analysis fixes one of the model parameters in terms of the others and constrains the rest. In conjunction with a suitable likelihood energy, we apply the model to the extraction of tree crowns from aerial imagery, and show that the new model outperforms other techniques.

2 - Higher-Order Active Contour Energies for Gap Closure. M. Rochery and I. H. Jermyn and J. Zerubia. Research Report 5717, INRIA, France, October 2005. Keywords : Road network, Continuity, Gap closure, Higher-order, Active contour, Shape. @TECHREPORT{RR_5717, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {Higher-Order Active Contour Energies for Gap Closure}, year = {2005}, month = {October}, institution = {INRIA}, type = {Research Report}, number = {5717}, address = {France}, url = {http://hal.inria.fr/inria-00070300/fr/}, pdf = {https://hal.inria.fr/file/index/docid/70300/filename/RR-5717.pdf}, ps = {http://hal.inria.fr/docs/00/07/03/00/PS/RR-5717.ps}, keyword = {Road network, Continuity, Gap closure, Higher-order, Active contour, Shape} } Résumé : L'un des principaux problèmes lors de l'extraction de réseaux linéiques dans des images, et en particulier l'extraction de réseaux routiers dans des images de télédétection, est l'existence d'interruptions dans les données, causées, par exemple, par des occultations. Ces interruptions peuvent mener à des trous dans le réseau extrait qui n'existent pas dans le réseau réel. Dans ce rapport, nous décrivons une énergie de contour actif d'ordre supérieur qui, en plus de favoriser les régions composées de bras fins et connectés entre eux, inclut un terme d'a priori qui pénalise les configurations du réseau où des extremités proches et se faisant face apparaissent. L'apparition dans le réseau extrait de ces configurations est donc moins probable. Si des extremités proches et se faisant face apparaissent pendant l'évolution par descente de gradient utilisée pour minimiser l'énergie, le nouveau terme dans l'énergie crée une attraction entre ces extremités, qui se rapprochent donc l'une de l'autre et se rejoignent, fermant ainsi le trou entre elles. Pour minimiser l'énergie, nous développons des techniques spécifiques pour traiter les derivées d'ordre élevé qui apparaissent dans l'équation de descente de gradient. Nous présentons des résultats d'extraction automatique de réseaux routiers à partir d'images de télédétection, montrant ainsi la capacité du modèle à surmonter les interruptions. Abstract : One of the main difficulties in extracting line networks from images, and in particular road networks from remote sensing images, is the existence of interruptions in the data caused, for example, by occlusions. These can lead to gaps in the extracted network that do not correspond to gaps in the real network. In this report, we describe a higher-order active contour energy that in addition to favouring network-like regions composed of thin arms joining at junctions, also includes a prior term that penalizes network configurations containing `nearby opposing extremities', and thereby makes their appearance in the extracted network less likely. If nearby opposing extremities form during the gradient descent evolution used to minimize the energy, the new energy term causes the extremities to attract one another, and hence to move towards one another and join, thus closing the gap. To minimize the energy, we develop specific techniques to handle the high-order derivatives that appear in the gradient descent equation. We present the results of automatic extraction of networks from real remote-sensing images, showing the ability of the model to overcome interruptions.

3 - Higher Order Active Contours. M. Rochery and I. H. Jermyn and J. Zerubia. Research Report 5656, INRIA, France, August 2005. Keywords : Active contour, Higher-order, Road network, Shape, Prior. @TECHREPORT{RR_5656, author = {Rochery, M. and Jermyn, I. H. and Zerubia, J.}, title = {Higher Order Active Contours}, year = {2005}, month = {August}, institution = {INRIA}, type = {Research Report}, number = {5656}, address = {France}, url = {https://hal.inria.fr/inria-00070352}, pdf = {https://hal.inria.fr/file/index/docid/70352/filename/RR-5656.pdf}, ps = {https://hal.inria.fr/docs/00/07/03/52/PS/RR-5656.ps}, keyword = {Active contour, Higher-order, Road network, Shape, Prior} } Résumé : Nous introduisons une nouvelle classe de contours actifs qui offre des perspectives intéressantes pour la modélisation des régions et des formes, et nous appliquons un cas particulier de ces modèles à l'extraction de réseaux linéiques dans des images satellitaires et aériennes. Les nouveaux modèles sont des fonctionnelles polynômiales arbitraires sur l'espace des contours, et généralisent ainsi les fonctionnelles linéaires utilisées dans les modèles classiques de contours actifs. Alors que les fonctionnelles classiques s'écrivent avec de simples intégrales sur le contour, les nouvelles énergies sont définies comme des intégrales multiples, décrivant ainsi des interactions de longue portée entre les différents ensembles de points du contour. Utilisées comme des termes d'a priori, les fonctionnelles décrivent des familles de contours aux propriétés géométriques complexes, sans faire référence à une forme spécifique et sans nécessiter l'estimation de la position. Utilisées comme des termes d'attache aux données, elles permettent de décrire des interactions multi-points entre le contour et les données. Afin de minimiser ces énergies, nous adoptons la méthodologie des courbes de niveau. Les forces dérivées des énergies sont cependant non locales, et nécessitent une extension des méthodes de courbes de niveau standard. Les réseaux sont une famille de formes d'une grande importance dans de nombreuses applications et en particulier en télédétection. Pour les modéliser, nous faisons un choix particulier d'énergie quadratique qui décrit des structures branchées et nous ajoutons un terme d'attache aux données qui lie les données et la géométrie du contour au niveau des paires de points du contour. Des résultats d'extraction prometteurs sont montrés sur des images réelles. Abstract : We introduce a new class of active contour models that hold great promise for region and shape modelling, and we apply a special case of these models to the extraction of road networks from satellite and aerial imagery. The new models are arbitrary polynomial functionals on the space of boundaries, and thus greatly generalize the linear functionals used in classical contour energies. While classical energies are expressed as single integrals over the contour, the new energies incorporate multiple integrals, and thus describe long-range interactions between different sets of contour points. As prior terms, they describe families of contours that share complex geometric properties, without making reference to any particular shape, and they require no pose estimation. As likelihood terms, they can describe multi-point interactions between the contour and the data. To optimize the energies, we use a level set approach. The forces derived from the new energies are non-local however, thus necessitating an extension of standard level set methods. Networks are a shape family of great importance in a number of applications, including remote sensing imagery. To model them, we make a particular choice of prior quadratic energy that describes reticulated structures, and augment it with a likelihood term that couples the data at pairs of contour points to their joint geometry. Promising experimental results are shown on real images.

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