python霍夫直线检测

import numpy as np
import cv2
import matplotlib.pyplot as plt

img = cv2.imread("rili.jpg",0)
edges = cv2.Canny(img,50,150)
plt.imshow(edges,cmap=plt.cm.gray)

lines = cv2.HoughLines(edges,0.8,np.pi/180,150)

for line in lines:
    rho, theta = line[0]
    a = np.cos(theta)
    b = np.sin(theta)
    x0 = rho*a
    y0 = rho*b
    x1 = int(x0+1000*(-b))
    y1 = int(y0+1000*a)
    x2 = int(x0-1000*(-b))
    y2 = int(y0-1000*a)
    cv2.line(img,(x1,y1),(x2,y2),(0,255,0))

plt.imshow(img[:,:,::-1])