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Bayesian Fusion of Multi-band Images: A Powerful Tool for Super-resolution

20 Septembre 2015


Catégorie : Soutenance de thèse


Soutenance de thèse de Qi WEI : "Bayesian Fusion of Multi-band Images: A Powerful Tool for Super-resolution"

Date : 24 Septembre 2015, 10h
Lieu : INP-ENSEEIHT Toulouse

 

Soutenance de thèse de Qi WEI : "Bayesian Fusion of Multi-band Images: A Powerful Tool for Super-resolution"

Date : 24 Septembre 2015, 10h
Lieu : INP-ENSEEIHT Toulouse

Composition du Jury :

  • M. Christophe COLLET, Professeur à Université de Strasbourg (Examinateur)
  • M. Cédric RICHARD, Professeur à Université de Nice (Rapporteur)
  • M. Paul SCHEUNDERS, Professeur à University of Antwerp (Rapporteur)
  • M. José BIOUCAS-DIAS, Senior Researcher à Instituto Superior Técnico, University of Lisbon (Examinateur)
  • M. Xavier BRIOTTET, ingénieur de recherche, ONERA (Examinateur)
  • Mme Gwendoline BLANCHET, ingénieur de recherche, CNES (Examinateur)
  • M. Jean-Yves TOURNERET, Professeur, INP Toulouse (Directeur de thèse)
  • M. Nicolas DOBIGEON, Maître de Conférences, INP Toulouse (Co-Directeur de thèse)

Abstract :

Hyperspectral (HS) imaging, which consists of acquiring a same scene in several hundreds of contiguous spectral bands (a three dimensional data cube), has opened a new range of relevant applications, such as target detection, classification and spectral unmixing. However, while HS sensors provide abundant spectral information, their spatial resolution is generally more limited. Thus, fusing the HS image with other highly resolved images of the same scene, such as multispectral (MS) or panchromatic (PAN) images is an interesting problem. The problem of fusing a high spectral and low spatial resolution image with an auxiliary image of higher spatial but lower spectral resolution, also known as multi-resolution image fusion, has been explored for many years. From an application point of view, this problem is also important as motivated by recent national programs, e.g., the Japanese next-generation space-borne hyperspectral image suite (HISUI), which fuses co-registered MS and HS images acquired over the same scene under the same conditions. Bayesian fusion allows for an intuitive interpretation of the fusion process via the posterior distribution. Since the fusion problem is usually ill-posed, the Bayesian methodology offers a convenient way to regularize the problem by defining appropriate prior distribution for the scene of interest.

The aim of this thesis is to study new multi-band image fusion algorithms to enhance the resolution of hyperspectral image. In the first chapter, a hierarchical Bayesian framework is proposed for multi-band image fusion by incorporating forward model, statistical assumptions and Gaussian prior for the target image to be restored. To derive Bayesian estimators associated with the resulting posterior distribution, two algorithms based on Monte Carlo sampling and optimization strategy have been developed. In the second chapter, a sparse regularization using dictionaries learned from the observed images is introduced as an alternative of the naive Gaussian prior proposed in Chapter 1 to regularize the ill-posed problem. Identifying the supports jointly with the dictionaries circumvented the difficulty inherent to sparse coding. To minimize the target function, an alternate optimization algorithm has been designed, which accelerates the fusion process magnificently comparing with the simulation-based method. In the third chapter, by exploiting intrinsic properties of the blurring and downsampling matrices, a much more efficient fusion method is proposed thanks to a closed-form solution for the Sylvester matrix equation associated with maximizing the likelihood. The proposed solution can be embedded into an alternating direction method of multipliers or a block coordinate descent method to incorporate different priors or hyper-priors for the fusion problem, allowing for Bayesian estimators. In the last chapter, a joint multi-band image fusion and unmixing scheme is proposed by combining the well admitted linear spectral mixture model and the forward model. The joint fusion and unmixing problem is solved in an alternating optimization framework, mainly consisting of solving a Sylvester equation and projecting onto a simplex resulting from the non-negativity and sum-to-one constraints. The simulation results conducted on synthetic and semi-synthetic images illustrate the advantages of the developed Bayesian estimators, both qualitatively and quantitatively.