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Spatially-Variant Mathematical Morphology: Theory and Applications

    Initially, the focus of mathematical morphology was devoted to translation-invariant operators. However, the translation-invariance assumption is not appropriate for many applications like traffic control analysis, range imagery, adaptive morphological filtering, shape representation, adaptive image decomposition and minimal image representation for coding and compression. These applications and many more clearly illustrate the need to develop a spatially-variant (i.e., non-necessarily translation-invariant) mathematical morphology theory that unifies all of the algorithms proposed thus far into a comprehensive mathematical framework.

    We proposed a general theory of Spatially-Variant (SV) mathematical morphology. This theory preserves the concept of structuring element that is crucial in the design of geometrical signal and image processing applications. We defined the elementary SV morphological operators and studied their properties. We subsequently derived a kernel representation of a large class of nonlinear and non-necessarily translation-invariant operators in terms of the elementary spatially-variant operators. The latter representation is a generalization of Matheron’s representation theorem for increasing and translation-invariant operators. The SV kernel representation is redundant, in the sense that a smaller subset of the SV kernel is sufficient for the representation of the SV operators. Thus, we provided sufficient conditions for the existence of the minimal basis of the kernel in terms of upper-semi-continuity in the hit-or-miss topology. The latter minimal basis representation is a generalization of Maragos’s minimal basis representation for increasing and translation-invariant operators. We used the theory of spatially-variant (SV) mathematical morphology to extend and analyze many important image processing applications like morphological image restoration and skeleton representation of binary images. In particular, we developed an algorithm to implement the SV morphological skeleton, which has a storage capacity gain twice as high as its translation-invariant counterpart.

Related publications:

  1.  N. Bouaynaya, M. Charif-Chefchaouni and D. Schonfeld, “Spatially-Variant Morphological Restoration and Skeleton Representation” , IEEE Transactions on Image Processing, vol. 15, no. 11, pp. 3579 - 3591, November 2006.  

  2.   N. Bouaynaya and D. Schonfeld, "Spatially-Variant morphological image processing: theory and applications", in Proceedings of SPIE Visual Communications and Image Processing (VCIP'06), vol. 6077, January 2006. (BEST STUDENT PAPER AWARD).  

  3.   N. Bouaynaya, M. Charif-Chefchaouni and D. Schonfeld, “ Theoretical Foundations of Spatially-Variant Mathematical Morphology Part I: Binary Images”, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 30, no. 5, May 2008.  

  4.   N. Bouaynaya and D. Schonfeld, “ Theoretical Foundations of Spatially-Variant Mathematical Morphology Part II: Gray-Level Images”, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 30, no. 5, May 2008.