“…These algorithms can be mainly divided into two categories: the transformed coefficient fusion method and the sub-block extraction method. The transformed coefficient fusion method proceeds in three steps: 1) transforming source images into another domain by some kind of transforming modes, for instance Laplacian pyramid [1], wavelet [2,3], contourlet [4][5][6], curvelet [7], empirical mode decomposition [8,9], non-negative matrix factorization [10], and so on; 2) integrating the transformed coefficients to get the composite coefficients by diverse schemes, such as the combination of the pixel-level fusion with some aspects of feature-level fusion [11]; 3) inversely transforming the composite coefficients to get the fused image. Different transforming modes have their respective advantages including multi-scale, localization, multidirection, anisotropy, etc.…”