138 research outputs found
Multivalued images curvatures: application to features detection and mean curvature flow restoration
No full texthttp://spiedigitallibrary.aip.org/vsearch/servlet/VerityServlet?KEY=PSISDG&smode=strresults&sort=rel&maxdisp=25&threshold=0&pjournals=PSISDG&possible1=Tremblais&possible1zone=article&SMODE=strsearch&OUTLOG=NO&deliveryType=spiedl&viewabs=PSISDG&key=DISPLAY&docID=2&page=0&chapter=0International audienceIn the present work we modelize multi-values 2D images as surfaces embbeded in space-features space. Using the differential geometric framework we then introduce an original definition of multi-values image curvatures. First we use these curvatures to detect valleys and ridges in color images. Then we generate a new non-linear color scale space based on a mean curvature flow. It leads to a powerful tool for denoising color images
De la résolution numérique des EDP à l'extraction de caractéristiques linéiques dans les images : application à la détection multi-échelles d'un arbre vasculaire
No full textOur work was motivated by a pratical problem aiming at studying and developping a general method to detect blood vessels from angiograms...Nos travaux ont été motivés par un problème pratique visant à étudier et à développer une méthode générale pour détecter les vaisseaux sanguins à partir de cinéangiographies. Il s'agit donc d'obtenir une bonne modélisation des vaisseaux, i.e. une caractér isation précise de leurs lignes centrales et de leurs diamètres. Une solution à cette problématique consiste à générer un espace multi-échelles qui grâce à ses différents niveaux de détails permet de traiter des artères de diamètres divers. Ces méthodes sont généralement mises en oeuvre en utilisant le formalisme des équations aux dérivées partielles (EDP) et celui de la géométrie différentielle. Les contributions de cette thèse sont multiples. Nous centrons tout d'abord nos travaux théoriques autour des traitements relatif s à la résolution des EDP en considérant ces traitements sous l'angle des méthodes itératives dites de recherche de point fixe. Ensuite, nous résolvons l'équation de la chaleur par une méthode de résolution à pas adaptatif originale, dite lambda-résolution. Ceci nous permet, en contrôlant la vitesse de convergence du processus, d'obtenir un filtre de diffusion isotrope, qui a la particularité de préserver les contours. Nous utilisons alors ce processus à des fins de débruitage et de segmentation d'images en niveaux de gris et couleur. Par ailleurs, nous introduisons une nouvelle EDP de rehaussement d'images, inspirée des filtres de choc et de la morphologie mathématique que nous couplons à l'analyse multi-échelles précédente de manière à obtenir un filtre de restauration d'images. Par la suite, la définition de courbures d'images vectorielles nous permet de proposer à la fois, une nouvelle {sc EDP} de lissage par courbure moyenne et une nouvelle méthode de détection des lignes centrales que nous appliquons sur des images couleur. Finalement, nous présentons une stratégie de détection multi-échelles des lignes centrales et des contours de l'arbre coronarien
A Fast multi-scale edges detection algorithm
No full texthttp://portal.acm.org/citation.cfm?id=987373.987374&coll=GUIDE&dl=GUIDE&CFID=72881883&CFTOKEN=56085086International audienceIn this paper we present a new explicit numerical scheme to approximate the solution of the linear diffusion filtering. This scheme is fast, stable, easy to program, applicable to arbitrary dimensions, and preserves the discontinuities of the objects. Experimental results support the efficiency of the proposed approach for the multi-scale detection of edges in greyscale, and color images
Direct experimental comparison between tomo-PIV and scanning tomo-PIV: wake flow behind a half-cylinder
No full textInternational audienceIn this paper, a direct experimental comparison is made between scanning and tomo-PIV, on an unsteady wake flow behind a half-cylinder. Several seeding densities are used in order to demonstrate the capacities and limitations of both techniques. For the scanning technique, the effect of particles elongation is investigated and the influence of the seeding density on the volume reconstruction for tomo-PIV is examinated. The results of the two techniques are compared in terms of volume and velocity fields
A Fast Multiscale Edge Detection Algorithm Based on a New Edge Preserving PDE Resolution Scheme
No full texthttp://www2.computer.org/portal/web/csdl/doi/10.1109/ICPR.2004.1334382International audienceIn this communication we present a new explicit numerical scheme to approximate the solution of the linear diffusion filtering. It allows to introduce a new edge preserving scheme which is fast, stable, easy to program and applicable to any dimensions. Our diffusion scheme is then put into a simple and original multi-scale edge detection algorithm. Some experimental results of the proposed approach for the multi-scale detection of edges in greyscale images are presented, as well as a comparison with other diffusion filtering schemes
Fast n-dimensional non linear filter
No full textInternational audienceIn this communication, we propose an original approach for the diffusion paradigm in image processing. Our starting point is the iterative resolution of partial differential equations (PDE) according to the explicit resolution scheme. We simply consider that this iterative process is nothing but a fixed point search. So, we obtain a convergence condition which applies to a large set of image processings PDE. That allows us to introduce a new smoothing process with strong abilities to preserve any structure of interest in the images. As an example, we here choose a linear isotropic diffusion for the denoising performances. Thus while resolving the equation of isotropic diffusion and by using an adaptive resolution parameter, we obtain a filtering process which can preserve arbitrary dimension object edges as one-dimensional signals, gray level images, color images, volumes, films, etc. We show the edge localization preserving property of the process and the computational effort is linear in size and the dimension of the object. We compare the complexity of the process with the Perona and Malik explicit scheme, and the Weickert AOS scheme. We establish that the computational effort of our scheme is lower than this of the two others. For illustration, we apply this new process to denoising of different kinds of medical images like MRI, angiograms, etc
Staging of the erotic self, autobiographical variations and literary games in Lydia Vázquez’s "Journal intime"
No full textEste artículo propone interesarse por la obra de Lydia Vázquez, Journal intime (2019), un texto de carácter autobiográfico que se inscribe plenamente en el ámbito de la literatura eróti-ca. La retórica propia de las escrituras del yoque presenta el relato será estudiada y tanto la estructura narrativa como las modalidades for-males y discursivas darán lugar a una reflexión. Se dedicará un espacio preferente al análisis del pacto autobiográfico que la autora establece con su lector. La especificidad del erotismo fe-menino será tratada a través de la visión que la autora ofrece de un erotismo que tiende hacia la expresión artística de la post-pornografía. El objetivo de este artículo es mostrar la singulari-dad que distingue la obra de Lydia Vázquez en el paisaje de la literatura erótica contemporánea de lengua francesaThis article proposes an interest in the work of Lydia Vázquez, Journal intime (2019), a text of an autobiographical nature that is fully within the scope of erotic literature. The rhetoric typi-cal of the writings of the I that presents the sto-ry will be studied and both the narrative struc-ture and the formal and discursive modalities will give rise to reflection. A preferential space will be dedicated to the analysis of the autobio-graphical pact that the author establishes with her reader. The specificity of female eroticism will be dealt with through the vision that the author offers of an eroticism that tends towar-ds the artistic expression of post-pornography. The aim of this article is to show the singularity that distinguishes Lydia Vázquez’s work in the landscape of contemporary French-language erotic literature
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No full texthttp://spiedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PSISDG004322000001001015000001&idtype=cvips&gifs=yesInternational audienceIn the present work we deal with the assistance to the diagnostic of coronaries stenosis from X-rays angiographies. Our goal is a 3D-reconstruction of the coronarian tree, therefore the extraction of some 2D characteristics is necessary. Here, we treat the problem of the 2D vessels medial axis extraction. The vessels geometry looks like valleys embedded in the image surface. Using differential geometry we can locally characterize medial axis as bottom lines of valleys. However, we have to calculate the image local derivatives, which is an ill-posed and noise sensitive problem. To overcome this drawback, we use a PDE based approach. We first consider the PDE?s numerical scheme as an iterative method known as fixed point search. So, we obtain a new method which assure the stability of the resolution process. The combinaison of this method and of an original PDE generates a scale-space where we can detect arteries of various diameters. We use then the eigenvalues and eigenvectors of the Weingarten endomorphism to define a new valley-ness measure. We have tested this technique on several angiographies, where the medial axis have well been extracted, even in presence of strong stenosis. Furthermore, the extracted axis are one pixel large and quite continuous
Parallelized 3D optical flow method for fluid mechanics applications
No full textInternational audienceIn this paper we address the problem of estimating the motion of fluids in 3D image sequences. We present a 3D extension of the second order div-curl regularization 2D optical flow equation first introduced by Corpetti et al.. In addition, we propose a multigrid and Message Passing Interface (MPI) parallelized implementation of the algorithm to handle the huge amount of data encountered in our applications. The performance of the resulting fluid flow estimator is demonstrated on a well representative motion synthetic pattern called Hill's spherical vortex. The suggested method should be a good alternative or complement to the well established techniques based on 3D cross correlation
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