I want to apply the following transformation to the image dataset.

N(w, h) = I(w, h) − G(w, h), (1) where N is the normalized image, I is the original image, and G is the Gaussian blurred image with kernel size 65*65 and 0 mean and standard deviation 10.

The code for gaussian blur is-
def gaussian_blur(img):
    image = cv2.GaussianBlur(image,(65,65),10)
    new_image = img - image
return image

I am really not sure how to convert it into lambda function as to use in generic transform.Any other advice on how to apply the above preprocessing step is also welcomed.