“…In transform domain, fusion methods can be classified as follows: pyramid-based methods, and wavelet transform methods. Based on the pyramid transformation: the laplacian pyramid, the gaussian pyramid, the contrast pyramid, and the morphological pyramid [7][8][9][10], these methods fail to involve spatial direction selectivity in the decomposition process, resulting in the block effect, and meanwhile produce many artifacts in the edge of the fused image affecting the fusion result; wavelet transform fusion methods, such as discrete wavelet transform, redundant wavelet transform and multiwavelet transform [11][12][13], only capture limited directional information, obtain limited information on edges and texture areas, and cannot clearly characterize the edges of the images. In recent years, with the rise of deep learning, Convolutional Neural Network (CNN) as an important branch of deep learning has stronger feature extraction capabilities than traditional methods, and is more suitable for image fusion [14][15][16].…”