A Non-Local Low-Rank Approach to Enforce Integrability

International audienceWe propose a new approach to enforce integrability using recent advances in non-local methods. Our formulation consists in a sparse gradient data-fitting term to handle outliers together with a gradient-domain non-local low-rank prior. This regularization has two main advantages : 1) the low-rank prior ensures similarity between non-local gradient patches, which helps recovering high-quality clean patches from severe outliers corruption, 2) the low-rank prior efficiently reduces dense noise as it has been shown in recent image restoration works. We propose an efficient solver for the resulting optimization formulation using alternate minimization. Experiments show that the new method leads to an important improvement compared to previous optimization methods and is able to efficiently handle both outliers and dense noise mixed together

Régularisation parcimonieuse pour le problème d'intégration en traitement d'images

International audienceLa reconstruction d'une surface ou image à partir d'un champ de gradient corrompu est une étape primordiale dans plusieurs applications en traitement d'images. Un tel champ peut contenir du bruit et des données aberrantes qui nuisent à la qualité de la reconstruction. On propose dans ce papier d'utiliser la parcimonie pour régulariser le problème, ainsi qu'une méthode efficace pour estimer une bonne solution du problème d'optimisation qui en résulte. Les expériences montrent que la méthode proposée permet d'améliorer considérablement la qualité de la reconstruction comparée aux méthodes précédentes

Handling noise in image deconvolution with local/non-local priors

International audienceNon-blind deconvolution consists in recovering a sharp latent image from a blurred image with a known kernel. Decon-volved images usually contain unpleasant artifacts due to the ill-posedness of the problem even when the kernel is known. Making use of natural sparse priors has shown to reduce ring-ing artifacts but handling noise remains limited. On the other hand, non-local priors have shown to give the best results in image denoising. We propose in this paper to combine both local and non-local priors to handle noise. We show that the blur increases the self-similarity within an image and thus makes non-local priors a good choice for denoising blurred images. However, denoising introduces outliers which are not Gaussian and should be well modeled. Experiments show that our method produces a better image reconstruction both visually and empirically compared to methods some popular methods

Novel reliable and dynamic energy-aware routing protocol for large scale wireless sensor networks

Wireless sensor networks (WSN) are made up of an important number of sensors, called nodes, distributed in random way in a concerned monitoring area. All sensor nodes in the network are mounted with limited energy sources, which makes energy harvesting on top of the list of issues in WSN. A poor communication architecture can result in excessive consumption, reducing the network lifetime and throughput. Centralizing data collection and the introduction of gateways (GTs), to help cluster heads (CHs), improved WSN life time significantly. However, in vast regions, misplacement and poor distribution of GTs wastes a huge amount of energy and decreases network’s performances. In this work, we describe a reliable and dynamic with energy-awareness routing (RDEAR) protocol that provides a new GT’s election approach taking into consideration CHs density, transmission distance and energy. Applied on 20 different networks, RDEAR reduced the overall energy consumption, increased stability zone and network life time as well as other compared metrics. Our proposed approach increased network’s throughput up to 75.92% , 67.7% and 9.78% compared to the low energy adaptive clustering hierarchy (LEACH), distributed energy efficient clustering (DEEC) and static multihop routing (SMR), protocols, respectively

Robust Surface Reconstruction via Triple Sparsity

International audienceReconstructing a surface/image from corrupted gradient fields is a crucial step in many imaging applications where a gradient field is subject to both noise and unlocalized outliers, resulting typically in a non-integrable field. We present in this paper a new optimization method for robust surface reconstruction. The proposed formulation is based on a triple sparsity prior : a sparse prior on the residual gradient field and a double sparse prior on the surface it- self. We develop an efficient alternate minimization strategy to solve the proposed optimization problem. The method is able to recover a good quality surface from severely cor- rupted gradients thanks to its ability to handle both noise and outliers. We demonstrate the performance of the pro- posed method on synthetic and real data. Experiments show that the proposed solution outperforms some existing meth- ods in the three possible cases : noise only, outliers only and mixed noise/outliers

Low-Rankness Transfer for Realistic Denoising

International audienceCurrent state-of-the-art denoising methods such as non-local low-rank approaches have shown to give impressive results. They are however mainly tuned to work with uniform Gaussian noise corruption and known variance, which is far from the real noise scenario. In fact, noise level estimation is already a challenging problem and denoising methods are quite sensitive to this parameter. Moreover, these methods are based on shrinkage models that are too simple to reflect reality, which results in over-smoothing of important structures such as small-scale text and textures. We propose in this paper a new approach for more realistic image restoration based on the concept of low-rankness transfer (LRT). Given a training clean/noisy image pair, our method learns a mapping between the non-local noisy singular values and the optimal values for denoising to be transfered to a new noisy input. One single image is enough for training the model and can be adapted to the noisy input by taking a correlated image. Experiments conducted on synthetic and real camera noise show that the proposed method leads to an important improvement both visually and in terms of PSNR/SSIM

Fast Multi-Scale Detail Decomposition via Accelerated Iterative Shrinkage

International audienceWe present a fast solution for performing multi-scale detail decomposition. The proposed method is based on an accelerated iterative shrinkage algorithm, able to process high definition color images in real-time on modern GPUs. Our strategy to accelerate the smoothing process is based on the use of first order proximal operators. We use the approximation to both designing suitable shrinkage operators as well as deriving a proper warm-start solution. The method supports full color filtering and can be implemented efficiently and easily on both the CPU and the GPU. We demonstrate the performance of the proposed approach on fast multi-scale detail manipulation of low and high dynamic range images and show that we get good quality results with reduced processing time

Reconstructing an image from its edge representation

International audienceIn this paper, we show that a new edge detection scheme developed from the notion of transition in nonlinear physics, associated with the precise computation of its quantitative parameters (most notably singularity exponents) provide enhanced performances in terms of reconstruction of the whole image from its edge representation; moreover it is naturally robust to noise. The study of biological vision in mammals state the fact that major information in an image is encoded in its edges, the idea further supported by neurophysics. The first conclusion that can be drawn from this stated fact is that of being able to reconstruct accurately an image from the compact representation of its edge pixels. The paper focuses on how the idea of edge completion can be assessed quantitatively from the framework of reconstructible systems when evaluated in a microcanonical formulation; and how it redefines the adequation of edge as candidates for compact representation. In the process of doing so, we also propose an algorithm for image reconstruction from its edge feature and show that this new algorithm outperforms the well-known 'state-of-the-art' techniques, in terms of compact representation, in majority of the cases

Kernel-Based Laplacian Smoothing Method for 3D Mesh Denoising

International audienceIn this paper, we present an improved Laplacian smoothing technique for 3D mesh denoising. This method filters directly the vertices by updating their positions. Laplacian smoothing process is simple to implement and fast, but it tends to produce shrinking and oversmoothing effects. To remedy this problem, firstly, we introduce a kernel function in the Laplacian expression. Then, we propose to use a linear combination of denoised instances. This combination aims to reduce the number of iterations of the desired method by coupling it with a technique that leadsto oversmoothing. Experiments are conducted on synthetic triangular meshes corrupted by Gaussian noise. Results show that we outperform some existing methods in terms of objective and visual quality