Python的類型錯誤：「NoneType」對象具有在圖像處理中沒有屬性「__getitem__」

Question

import cv2 
import numpy as np 
import matplotlib.pyplot as plt 
def CannyThreshold(lowThreshold): 
      lowThreshold = cv2.getTrackbarPos('Min threshold','canny demo') 
      detected_edges = cv2.medianBlur(gray,5) 
      detected_edges=cv2.Canny(detected_edges,lowThreshold,lowThreshold*ratio,apertureSize = kernel_size) 
lines = cv2.HoughLines(detected_edges,1,np.pi/180,190) 
for rho,theta in lines[0]: 
    a= np.cos(theta) 
    b= np.sin(theta) 
    x0 = a*rho 
    y0 = b*rho 
    x1 = int(x0 + 1000*(-b)) 
    y1 = int(y0 + 1000*(a)) 
    x2 = int(x0 - 1000*(-b)) 
    y2 = int(y0 - 1000*(a)) 
    #print 'rho=',rho,' theta=',theta 
    cv2.line(frame,(x1,y1),(x2,y2),(0,0,255),2) 

cv2.imshow('canny demo',detected_edges) 
cv2.imshow('original',frame) 

lowThreshold = 23 
max_lowThreshold = 50 
ratio = 3 
kernel_size = 3 
cap = cv2.VideoCapture(0) 
cv2.namedWindow('canny demo') 
cv2.createTrackbar('Min threshold','canny demo',lowThreshold,max_lowThreshold, CannyThreshold) 

while(1): 
    ret, frame = cap.read() 
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY) 
    CannyThreshold(lowThreshold) # initialization 
if cv2.waitKey(1) == 27: 
    cap.release() 
    cv2.destroyAllWindows() 

上方我的代碼來檢測邊緣，然後在

我正在錯誤下面給出原始幀畫線在它：

Traceback (most recent call last): 
    File "D:\python_program\hough transform\canny_camera.py", line 37, in <module> 
    CannyThreshold(lowThreshold) # initialization 
    File "D:\python_program\hough transform\canny_camera.py", line 11, in CannyThreshold 
    for rho,theta in lines[0]: 
TypeError: 'NoneType' object has no attribute '__getitem__' 

Answer 1

lines = cv2.HoughLines(detected_edges,1,np.pi/180,190) 

此線可以是無，然後行[0]中錯誤結果