can someone help on this
It somewhat depends on what your goals are.
If you merely want to save each rectangle slip into separate images, a simple crop would do the trick. For instance the, pillow (PIL) library has this functionality see here.
If you want to warp each slip to be aligned, opencv (cv2) may be more helpful. If you grab the 4 corners, you can find a transformation matrix that will warp those corners to be from 0,0 to width,height. See the geometric transformation guide for one example.