“…An overview of these factors can be found in the survey by researchers in [ 3 ]. Using the computational domain as a classification criterion, there are two branches of existing JND models, i.e., the pixel domain (where JND thresholds are computed directly for each pixel) [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] and the transform domain (where the image is first transformed into a subband domain, and then JND thresholds are calculated for each subband) [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Nevertheless, both model types generally follow the same design philosophy of simulating the visual-masking effects of several elements before combining (multiplying or adding) them to obtain an overall JND estimation.…”