The Moore-Penrose pseudoinverse is a useful concept in dealing with optimization problems, as the determination of aŞleast squaresŤ solution of linear systems. A typical application of the Moore-Penrose inverse is its use in Image and signal Processing and Image restoration. The presented method in this article is based on the use of the Moore-Penrose generalized inverse of a matrix and provides us a fast computational algorithm for a fast and accurate digital image restoration. This article is an extension of the work presented in [7]; [8].
Theoretical background
The Moore-Penrose inverseWe shall denote by R r×m the algebra of all r × m real matrices. For T ∈ R r×m , R(T) will denote the range of T and N(T) the kernel of T. The generalized inverse T † is the unique matrix that satisfies the following four Penrose equations:where T * denotes the transpose matrix of T.Let us consider the equation Tx = b, T ∈ R r×m , b ∈ R r ,whereT is singular. If T is an arbitrary matrix, then there may be none, one or an infinite number of solutions, depending on whether b ∈ R(T) or not, and on the rank of T.B u ti fb / ∈ R(T), then the equation has no solution. Therefore, another point of view of this problem is the following: instead of trying to solve the equation Tx − b = 0, we are looking for a minimal norm vector u that minimizes the norm Tu − b . Note that this vector u is unique. So, in this case we consider the equation Tx = P R(T) b,whereP R(T) is the orthogonal projection on R(T). Since we are interested in the distance between Tx and b, it is natural to make use of T 2 norm.The following two propositions can be found in [12].Proposition 0.1. Let T ∈ R r×m and b ∈ R r , b / ∈ R(T).T h e n ,f o ru∈ R m , the following are equivalent:Let B = {u ∈ R m |T * Tu = T * b}. This set of solutions is closed and convex; it therefore has a unique vector u 0 with minimal norm. In fact, B is an affine manifold; it is of the form u 0 + N (T). In the literature (c.f. [12]), B is known as the set of the least square solutions. We shall make use of this property for the construction of an alternative method in image processing inverse problems.