Apply a Sobel filter to an image.

Sobel.py

import numpy as np
import Image
import scipy.ndimage as ndimage

def sobel(img):
    gx = ndimage.filters.convolve(img, np.array([[-1, 0, +1], [-2, 0, +2], [-1, 0, +1]]))
    gy = ndimage.filters.convolve(img, np.array([[+1, +2, +1], [0, 0, 0], [-1, -2, -1]]))
    
    imgout = np.sqrt(gx**2+gy**2)
    
    return imgout

img = np.array(Image.open('BW with PSF.tif'))
i = Image.fromarray(sobel(img))
i.save('BW with PSF sobel.tif')