“…Over the past few decades, several techniques have been proposed for pixel-level fusion. These include the Laplacian pyramid (LP) [5,41,43], the discrete wavelet transform (DWT) [11], the dual-tree complex wavelet transform (DTCWT) [20,21], the curvelet transform (CVT) [16,33], the non-subsampled contourlet transform (NSCT) theory [13,14], the multi-resolution singular value decomposition (MSVD) [32], guided filtering fusion (GFF) [24], autoencoder-based approaches [15], and other techniques [38]. Recently, deep learning-based fusion methods have also been developed, including the DenseFuse method [22], the RFN-Nest method [23], the SDNet method [49], the SeAFusion method [40], image fusion based on proportional maintenance of gradient and intensity (PMGI) [50], image fusion based on convolutional neural network (IFCNN) [17,51], and fusion method based on generative adversarial networks (FusionGAN) [26].…”