I know something about Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)) .
The first (0.5, 0.5, 0.5) is the mean of R G B.
The second is the std of R G B .
0.5 is a roughly digit.
The general statistics given on pytorch ：
mean=[0.485, 0.456, 0.406],std=[0.229, 0.224, 0.225])