8.opencv-python；cv2库；形态学；梯度运算=膨胀-腐蚀

import cv2 #opencv读取的格式是BGR
import numpy as np
import matplotlib.pyplot as plt#Matplotlib是RGB
%matplotlib inline 
 
# 读取
img=cv2.imread('lena.jpg')
img_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
 
# 图像二值化
ret, thresh1 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_BINARY)

# 膨胀与腐蚀分别展示
kernel = np.ones((3,3),np.uint8) 
dilate = cv2.dilate(thresh1,kernel,iterations = 1)
erosion = cv2.erode(thresh1,kernel,iterations = 1)

res = np.hstack((dilate,erosion))

cv2.imshow('res', res)
cv2.waitKey(0)
cv2.destroyAllWindows()

# 梯度=膨胀-腐蚀
gradient = cv2.morphologyEx(thresh1, cv2.MORPH_GRADIENT, kernel)

cv2.imshow('gradient', gradient)
cv2.waitKey(0)
cv2.destroyAllWindows()

膨胀与腐蚀分别展示

 梯度=膨胀-腐蚀

 梯度，轮廓，用圆来理解，大圆减小圆结果。