Image to sketch Python

#import the libraries
import numpy as np
import imageio
import scipy.ndimage
import cv2

#lets create a variable which will store a image
img="my.jpg"

def grayscale(rgb):
     return np.dot(rgb[...,:3],[0.299,0.587,0.114]) #this is the formuleto convert an image to black and white image

#this function will convert your image into sketch formate
 def dodge(front,back):
    result=front*255/(255-back)
    result[result>255]=255
    result[result==255]=255
    return result.astype('uint8')

s=imageio.imread("my.jpg")
g=grayscale(s)
i=255-g

#lets create blurred image
b=scipy.ndimage.filters.gaussian_filter(i,sigma=10)
r=dodge(b,g)

#write the name of the picture which you have to want
cv2.imwrite("my_sketch.png",r)