“…eir crucial idea is the discovery of the mapping relationship between LR and HR exemplar image patch pairs. According to the establishment of a mapping relationship, learning-based methods generally include neighbor-based approaches [14,15,18,19], sparse representation-based approaches [8,[20][21][22][23][24][25], example regression-based approaches [9,10,12,13], and deep learning-based approaches [11,16,17,[26][27][28][29][30][31][32].…”