after converting your torch tensor back to opencv ndarray, if you do an imshow the image will appear slightly darker due to standard normalization.
def inverse_normalize(tensor, mean, std):
    for t, m, s in zip(tensor, mean, std):
        t.mul_(s).add_(m)
    return tensor

input = inverse_normalize(tensor=input, mean=(0.485, 0.456, 0.406), std=(0.229, 0.224, 0.225))

you should inverse normalize your torch tensor before converting to numpy array if the image colours matter to you