Christian Germain

Seismic Fault Preserving Diffusion

This paper focuses on the denoising and enhancing of 3-D reflection seismic data. We propose a pre-processing step based on a non linear diffusion filtering leading to a better detection of seismic faults. The non linear diffusion approaches are based on the definition of a partial differential equation that allows us to simplify the images without blurring relevant details or discontinuities. Computing the structure tensor which provides information on the local orientation of the geological layers, we propose to drive the diffusion along these layers using a new approach called SFPD (Seismic Fault Preserving Diffusion). In SFPD, the eigenvalues of the tensor are fixed according to a confidence measure that takes into account the regularity of the local seismic structure. Results on both synthesized and real 3-D blocks show the efficiency of the proposed approach.

Delineation of vine parcels by segmentation of high resolution remote sensed images

Field delineation is an essential preliminary step for the design of management maps for grape production. In this paper, we propose a new algorithm for the segmentation of vine fields based on high-resolution remote sensed images. This algorithm takes into account the textural properties of vine images. It leads to the computation of a textural attribute on which a simple thresholding operation allows to discriminate between vine field and non-vine field pixels. The feasibility of the automatic delineation is illustrated on a range of vineyard images with various inter-row distances, grass covers, perspective distortions and side perturbations. In most cases it produces precise delineation of field borders while the parcel under consideration remains separate from the rest of the image.

Estimating local multiple orientations

This paper focuses on the estimation of local orientation in an image where several orientations exist at the same location and at the same scale. Within this framework, Isotropic and Recursive Oriented Network (IRON), an operator based on an oriented network of parallel lines is introduced. IRON uses only a few parameters. Beyond the choice of a specific line homogeneity feature, the size and the shape of the network can be tuned. These parameters allow us to adapt our operator to the image studied. The implementation we propose for the network is recursive, relying on the rotation of the image instead of the rotation of the operator. IRON can proceed on a small computing support, and thus provides a local estimation of orientations. Herein, we test IRON on both synthetic and real images. Compared to some other orientation estimation methods such as Gabor filters or Steerable filters, our operator detects multiple orientations with both better accuracy and noise robustness, at a competitive computational cost thanks to its recursivity. Moreover, IRON offers better selectivity, particularly at small scale.

An image-guided atomistic reconstruction of pyrolytic carbons

A method for the generation of atomistic models of dense nanotextured carbons is presented. This method is based on the statistical analysis of high resolution transmission electron microscopy images and their three-dimensional (3D) extension through image synthesis under constraint. The resulting 3D images then serve as an external potential bringing the atoms to settle preferentially on the black areas during a conventional simulated annealing simulation. Application of this method to the case of two laminar pyrocarbons, differing in their degree of disorder, highlights the promising nature of this approach.

Multiscale estimation of vector field anisotropy application to texture characterization

This paper deals with the characterization of the anisotropy of textured images. It is well known that either the dominant direction or the texture anisotropy strongly depends on the scale used for the observation. In this paper we propose a new operator for the estimation of the dominant direction, the directional mean vector (DMV), which can be computed at any observation scale. Then, we present a new indicator for the estimation of the DMV field anisotropy. This indicator, called Iso, is computed at a given observation scale. Iso is based on the computation of the DMV field local differences. It is shown that the evolution of Iso versus the observation scale gives a curve which simultaneously characterizes the anisotropy of the texture and the size of the textural patterns. In order to establish this property, we build a specific texture model which allows to assess an analytical expression for Iso. Finally, Iso is applied to the characterization of various images including synthetic textures, Brodatz textures and composite material images.

Spectral–Spatial Classification of Hyperspectral Images Using ICA and Edge-Preserving Filter via an Ensemble Strategy

To obtain accurate classification results of hyperspectral images, both spectral and spatial information should be fully exploited in the classification process. In this paper, we propose a novel method using independent component analysis (ICA) and edge-preserving filtering (EPF) via an ensemble strategy for the classification of hyperspectral data. First, several subsets are randomly selected from the original feature space. Second, ICA is used to extract spectrally independent components followed by an effective EPF method, to produce spatial features. Two strategies (i.e., parallel and concatenated) are presented to include the spatial features in the analysis. The spectral-spatial features are then classified with a random forest or a rotation forest classifier. Experimental results on two real hyperspectral data sets demonstrate the effectiveness of the proposed methods. A sensitivity analysis of the new classifiers is also performed.

A new adaptive framework for unbiased orientation estimation in textured images

This paper focuses on directional texture analysis. We propose a new approach for orientation estimation. This approach hinges on two classes of convolution masks, i.e. the gradient and the valleyness operators. We provide a framework for their optimization regarding bias reduction and noise robustness. As the gradient and the valleyness operators are complementary, we propose a combination named GV-JOE. This combination consists in using the gradient on inflexion pixels, the valleyness on crests and valleys, and a linear mixture of both elsewhere. We implement an adaptive selection of the size of our operators, in order to take into account the variations of the texture scale in the image. We apply our approach both on synthetic and natural textures. These experiments show that, when used separately, both classes of operators are more accurate than classical derivative approaches. In noisy cases, the GV-JOE implementation improves the robustness of our operators without affecting their accuracy. Moreover, compared to well-known orientation estimators, it gives the best estimates in the most difficult cases i.e. for high-frequency textures and low SNR.

Retrieval of Forest Stand Age From SAR Image Texture for Varying Distance and Orientation Values of the Gray Level Co-Occurrence Matrix

Data on forest variables (e.g., biomass, trunk height, density) are necessary for environmental and forest management applications. It has been shown that texture can be used instead of the usual σo/age relationships at P-band to retrieve plantation forest parameters, but the analysis of σo spatial characteristics has not been fully explored. The aim of this letter is to investigate the relationships between stand age (which is correlated to forest variables) and texture descriptors calculated from statistics generated by the gray-level co-occurrence matrix for varying distance d, and orientation α, values used to calculate the matrix. Synthetic aperture radar images are P-band airborne data acquired by the ONERA RAMSES instrument over a controlled homogeneous test site located in the Landes region, France. It is found that texture descriptors contrast, inverse difference moment, homogeneity, and correlation are strongly influenced by the parameters (d, α) related to forest stand structure (forest rows, stand density) and image resolution. In contrast, energy and entropy are observed to be highly correlated to stand age and displayed a stable performance whatever the distance and orientation parameters (d, α), thus rendering them a good contender as an alternative to the usual σo based relationships applied to this type of forest.

Wavelet-Based Texture Features for the Classification of Age Classes in a Maritime Pine Forest

This letter evaluates the potential of wavelet-based texture modeling for the classification of stand age in a managed maritime pine forest using very high resolution panchromatic and multispectral PLEIADES data. A cross-validation approach based on stand age reference data is used to compare classification performances obtained from different multivariate models (multivariate Gaussian, spherically invariant random vector (SIRV)-based models, and Gaussian copulas) and from co-occurrence matrices. Results show that the multivariate modeling of the spatial dependence of wavelet coefficients (particularly when using the Gaussian SIRV model) outperforms the use of features derived from co-occurrence matrices. Simultaneously adding features representing the color dependence and leveling the dominant orientation in anisotropic forest stands enhances the classification performances. These results confirm the ability of such wavelet-based multivariate models to efficiently capture the textural properties of very high resolution forest data and open up perspectives for their use in the mapping of monospecific forest structure variables.

New operators for optimized orientation estimation

This paper focuses on directional textures. It provides a new framework for the design of convolution masks dedicated to orientation estimation. We propose a new technique based on the combination of two complementary operators: a gradient-based operator which is adapted to sloped regions and a valleyness detector which fits the crests and valleys. On each operator, a double optimization procedure is carried out with respect to bias and noise sensitivity reduction. The procedure is generic and applies to any kind of underlying directional texture. Experiments on a synthetic sine wave texture and on natural textures are provided and show the efficiency and the relevance of our approach.