Another question: to compute the mean and std, should I use the raw images or the transformed with the same transforms that I am going to use for the training dataset  (such as RandomRotation, ColorJitter etc.)?
The problem is that due to the randomness in such transformations, the mean and the std will not be the same at each training iteration. On the other hand, if I use the mean and the std of the raw images, during the training the model sees transformed images which have different mean and std from the raw images.