raw invert image and grayscale

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Python

image-processing

Hello,

I have a code that checks a folder for jpg files. Then invert and crop it and copy it in another folder. All i need is doing same thing for a raw image(NEF file). I need to make them grayscale too.

Here is my code for jpg images;

import cv2
import numpy as np
import filecmp
import time
import os


old=set(os.listdir('C:\images'))
while (1):
    new = set(os.listdir('C:\images'))
    if(new!=old):
        difference = new.difference(old)
        for images in difference:


            img = cv2.imread('C:\images/' + images)
            
            inverted = (255-img)
            inverted2 = inverted[148:3925 , 732:5157]

            cv2.imwrite('C:/data/' + images ,inverted2)
            
    time.sleep(3)
    old =  new

i downloaded rawPy and PythonMagick too but i don't know how to use them in my code.

How can i update my code for NEF files?