Multistep Detection of Oriented Structure in Complex Textures

International audienceIn the context of online industrial control, we propose a multistep method, based on mathematical morphology operators, to carry out the characterization of oriented structures in a complex texture environment. In a data base of about ten thousand patches, ten percent show various oriented structures. First we measure for each patch the x and y covariances, and apply pyramids of dilations-erosions and openings-closings using linear structuring elements. Second we transform the resulting pyramid images into usable condensed information. All the measures for each patch set up texture descriptors. For each of them we apply a Principal Components Analysis (PCA) to sum up the information. Then we use a Linear Discriminant Analysis (LDA) on the principal axes which carry the most information and analyze in the LDA space the distribution of the two types of patches to reach 99.45% of sensitivity and 99.61% of specificity

New Operator Based on a Multi Support Point Algorithm Applied to Feature Extraction

International audienceIn the context of quality control, we propose a new operator using multi support points to highlight local perturbations on flat surfaces. We compare the design of this operator with different gradients and residues in their ability to extract small perturbations as well as their efficiency on large surface. The operator is defined as a weighted differential operator evaluated on each point. It is designed to extract a region with a high slope followed by a plateau with a given width. It has a low computational complexity and it could be vectorized

Uniformisation de l'éclairage en imagerie rétinienne : Application pour les images d'autofluorescence du fond d'œil

Texte intégral accessible en ligne à http://documents.irevues.inist.fr/bitstream/handle/2042/28924/rashidchaudhry_313.pdfInternational audienceDans cet article nous proposons une méthode originale pour corriger l'éclairage inhomogène des images de la rétine. Notre méthode utilise la convolution de l'image par un filtre gaussien de taille appropriée définie automatiquement par l'analyse de la courbe d'entropie de l'image corrigée. La luminosité moyenne de l'image originale est conservée ainsi que les structures et les lésions.Title: Uniformization of lighting in retinal imaging : Application to autofluorescence images of fundus oculiAbstract: In this paper, we propose an original method for the correction of inhomogeneous illumination in the retinal images. Our method uses the convolution of an image by Gaussian filter of an appropriate size. The size of the Gaussian filter is automatically determined by the analysis of entropy curve of the corrected image. The original brightness of the image is preserved as well as the retinal structural and lesions

Ophthalmologic Image Registration Based on Shape-Context: Application to Fundus Autofluorescence (FAF) Images

Online access to subscriber only at http://www.actapress.com/Content_Of_Proceeding.aspx?ProceedingID=494International audienceA novel registration algorithm, which was developed in order to facilitate ophthalmologic image processing, is presented in this paper. It has been evaluated on FAF images, which present low Si gnal/Noise Ratio (SNR) and variations in dynamic grayscale range. These characteristics complicate the registration process and cause a failure to area-based registration techniques [1, 2] . Our method is based on shape-context theory [3] . In the first step, images are enhanced by Gaussian model based histog ram modification. Features are extracted in the next step by morphological operators, which are used to detect an approximation of vascular tree from both reference and floating images. Simplified medial axis of vessels is then calculated. From each image, a set of control points called Bifurcation Points (BPs) is extracted from the medial axis through a new fast algorithm. Radial histogram is formed for each BP using the medial axis. The Chi2 distance is measured between two sets of BPs based on radial histogram. Hungarian algorithm is applied to assign the correspondence among BPs from reference and floating images. The algorithmic robustness is evaluated by mutual information criteria between manual registration considered as Ground Truth and automatic one

Multi-streaming and multi-GPU optimization for a matched pair of Projector and Backprojector

International audienceIterative reconstruction methods are used in X-ray Computed Tomography in order to improve the quality of reconstruction compared to filtered backprojection methods. However, these methods are computationally expensive due to repeated projection and backprojection operations. Among the possible pairs of projector and backprojector, the Separable Footprint (SF) pair has the advantage to be matched in order to ensure the convergence of the reconstruction algorithm. Nevertheless, this pair implies more computations compared to unmatched pairs commonly used in order to reduce the computation time. In order to speed up this pair, the projector and the backprojector can be parallelized on GPU. Following one of our previous work, in this paper, we propose a new implementation which takes benefits from the factorized calculations of the SF pair in order to increase the number of data handled by each thread. We also describe the adaptation of this implementation for multi-streaming computations. The method is tested on large volumes of size 1024 3 and 2048 3 voxels

Impact of cellulose ethers on the cement paste microstructure

ISBN = 3-87264-022-4 7 pagesInternational audienceComplementary investigation tools (2D and 3D observations by optical microscopy and fast X-ray microtomography and then image analysis) were developed in order to examine the effects of cellulose ethers on the cement paste microstructure. The obtained results show that the presence of cellulose ether may induce an increase of both 50-250 µm-diameter air voids. The chemistry of the cellulose ethers appears as a main controlling factor of this porous media modification. In particular, cellulose ethers seems to play an important role on the air bubbles morphological characteristics, the content of air volume and the stabilisation of the porosity from the fresh cement paste to the hardened cement paste

Analyse morphologique 3D de particules de forme complexes: application aux intermétalliques dans les alliages d'aluminium

In this PhD-thesis, the studied material is an aluminium alloys 5182 containing two particles types: Alx(Fe,Mn) and Mg2Si. During industrial rolling, particles are broken up, and redistributed in the volume of the sheet.As particles controls surface aspect and formability of the final sheet, the work presented is based on two issues: to highlight volume distribution of intermetallic particles, and to characterize their three-dimensional shapes during the rolling process. Thus, samples extracted to different steps of the rolling process are been scanned by X ray micro tomography (performed at the ESRF). The obtained three dimensional images are segmented by a multi class thresholding method. Extraction of each particle type is allowed. A data basis containing each individualized particles is created. It ensures to reconstruct the material binary image and also to work particle by particle.The particles dispersion is highlight by the graph of distances and the covariance study. The analysis of linear erosion and covariance allows to model the material by a probabilistic Boolean model with spherical primary grains.A set of morphological parameters characterizes the intermetallic particles three dimensional complex shapes. A principal components analysis is performed to sum up the information. In the obtained subspace, particles are classified into 5 families of shapes. Their evolution is followed during the rolling process.Le matériau étudié dans cette thèse est un alliage d'aluminium 5182 contenant des particules intermétalliques de deux types : Alx(Fe,Mn) et Mg2Si. Au cours du laminage industriel, les particules sont brisées et redistribuées dans le volume de la tôle. Or, les particules intermétalliques contrôlent à la fois l'aspect de surface et la formabilité de la tôle finale.Le travail présenté dans la thèse s'articule autour de deux problématiques : mettre en évidence la distribution volumique des particules intermétalliques dans le volume de la tôle, et caractériser leur forme tridimensionnelle complexe au cours du laminage. Ainsi, des échantillons prélevés à différentes étapes du laminage sont observés par micro tomographie aux rayons X (réalisé à l'ESRF). Les images tridimensionnelles obtenues sont segmentées par la méthode de segmentation multi classe. Elle permet d'extraire chaque type de particule de l'alliage. Une base de donnée contenant chaque particule individualisée est créée. Elle permet de reconstruire l'image binaire du matériau et de travailler particule à particule.La dispersion des particules est mise en évidence par l'étude du graphe des distances et de la covariance. Puis l'analyse de l'érosion linéaire et de la covariance permet de modéliser le matériau par un modèle probabiliste de type schéma Booléen à grains primaires sphériques.Une batterie de paramètres morphologiques caractérise la forme tridimensionnelle complexe des particules. Une analyse en composantes principales est ensuite réalisée pour synthétiser l'information. Dans l'espace obtenu, les particules sont classées en cinq familles de forme. Enfin, leur évolution au cours du laminage est étudiée

Morphological analysis of complex three-dimensional particles. Application to aluminium alloy 5xxx

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