“…However, the most prevalent studies have focused only on some of these types of noise ( e.g ., Gaussian and Poisson). In particular, among many other techniques, histogram equalization (HE) ( Civit-Masot et al, 2020 ; Tartaglione et al, 2020 , Rezaul Karim et al, 2020 ), contrast limited adaptive histogram equalization (CLAHE) ( El-bana, Al-Kabbany & Sharkas, 2020 ; Saiz & Barandiaran, 2020 ; Maguolo & Nanni, 2021 ; Ramadhan et al, 2020 ), adaptive total variation method (ATV) ( Punn & Agarwal, 2021 ), white balance followed by CLAHE ( Siddhartha & Santra, 2020 ), intensity normalization followed by CLAHE (N-CLAHE) ( Horry et al, 2020 ; El Asnaoui & Chawki, 2020 ), Perona-Malik filter (PMF), unsharp masking (UM) ( Rezaul Karim et al, 2020 ), Bi-histogram equalization with adaptive sigmoid function (BEASF) ( Haghanifar et al, 2020 ), the gamma correction (GC) ( Rahman et al, 2021b ), histogram stretching (HS) ( Wang et al, 2021 ; Zhang et al, 2021 ), Moment Exchange algorithm (MoEx), CLAHE ( Lv et al, 2021 ), local phase enhancement (LPE) ( Qi et al, 2021 ), image contrast enhancement algorithm (ICEA) ( Canayaz, 2021 ), and Gaussian filter ( Medhi, Jamil & Hussain, 2020 ) are, as far as we are aware, the only adopted techniques in COVID-19 recognition to date. An overview of these works is listed in Table 1 .…”