python如何实现均值过滤？

import cv2
import numpy as np


def blur_demo(image):            
	"""
	均值模糊 : 去随机噪声有很好的去噪效果
	（1, 15）是垂直方向模糊，（15， 1）是水平方向模糊
	"""
    dst = cv2.blur(image, (1, 15))    
    cv2.imshow("avg_blur_demo", dst)

def median_blur_demo(image):    # 中值模糊  对椒盐噪声有很好的去燥效果
    dst = cv2.medianBlur(image, 5)
    cv2.imshow("median_blur_demo", dst)

def custom_blur_demo(image):
	"""
	用户自定义模糊
	下面除以25是防止数值溢出
	"""
    kernel = np.ones([5, 5], np.float32)/25   
    dst = cv2.filter2D(image, -1, kernel)
    cv2.imshow("custom_blur_demo", dst)

src = cv2.imread("./fapiao.png")
img = cv2.resize(src,None,fx=0.8,fy=0.8,interpolation=cv2.INTER_CUBIC)
cv2.imshow('input_image', img)

blur_demo(img)
median_blur_demo(img)
custom_blur_demo(img)

cv2.waitKey(0)
cv2.destroyAllWindows()