Opencv：霍夫线没有显示

Question

所以我试图在棋盘上获得hough线，但算法只能检测到一条线。我使用的是python 2.7和opencv 3.0。这是代码：

def applyHoughLineTransform():
    image1 = cv2.imread('pictures/board1.png',0)
    image2 = cv2.imread('pictures/board2.png',0)
    image3 = cv2.imread('pictures/board3.png')
    image4 = cv2.imread('pictures/board4.png')

    lines1 = cv2.HoughLines(image1,1,math.pi/180.0,5)
    lines2 = cv2.HoughLines(image2,1,math.pi/180.0,5)

    lines1 = lines1[0]
    lines2 = lines2[0]

    for rho,theta in lines1:
        print ('Rho and theta:',rho,theta)
        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 (x1,y1)
        print (x2,y2)

        cv2.line(image3,(x1,y1),(x2,y2),(0,0,255),2)

    for rho,theta in lines2:
        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))

        cv2.line(image4,(x1,y1),(x2,y2),(0,0,255),2)

    cv2.imwrite('pictures/board1.png',image1)
    cv2.imwrite('pictures/board2.png',image2)

    cv2.imshow('hough line 1',image3)
    cv2.imshow('hough line 2',image4)

这里是我执行hough line算法的canny edge图像：

以下是结果：

如你所见，非常蹩脚。 canny算法似乎提供了非常好的边缘来操作。我不完全确定我做错了什么。我想它与输入houghLines函数的参数有关。如果有人能指出我正确的方向（或完全解决我的问题:)）我将非常感激。这是我使用的教程网站的链接： http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_imgproc/py_houghlines/py_houghlines.html

Answer 1

OPENCV 3.1.0

从包中检查示例后，这是您应该在Opencv 3.0.0 +中使用它的方法

import cv2
import numpy as np
import math

image1 = cv2.imread('img.png')
gray=cv2.cvtColor(image1,cv2.COLOR_BGR2GRAY)
dst = cv2.Canny(gray, 50, 200)

lines= cv2.HoughLines(dst, 1, math.pi/180.0, 100, np.array([]), 0, 0)
#lines1 = cv2.HoughLines(image1,1,math.pi/180.0,5)
#lines2 = cv2.HoughLines(image2,1,math.pi/180.0,5)

#lines1 = lines1[0]
#lines2 = lines2[0]

a,b,c = lines.shape
for i in range(a):
    rho = lines[i][0][0]
    theta = lines[i][0][1]
    a = math.cos(theta)
    b = math.sin(theta)
    x0, y0 = a*rho, b*rho
    pt1 = ( int(x0+1000*(-b)), int(y0+1000*(a)) )
    pt2 = ( int(x0-1000*(-b)), int(y0-1000*(a)) )
    cv2.line(image1, pt1, pt2, (0, 0, 255), 2, cv2.LINE_AA)


cv2.imshow('image1',image1)
cv2.waitKey(0)
cv2.destoryAllWindows(0)

输出

Answer 2

解决此问题的方法是从opencv 3.0切换到2.4。现在我得到了我想要的所有线条。获得的经验教训......有一个原因是测试版！结果如下：

Answer 3

我在OpenCV 3.4中遇到了同样的问题。罪魁祸首是在numpy数组lines：

[[[  7.99000000e+02   1.57079637e+00]] 
 [[  9.39000000e+02   1.57079637e+00]]    
 [[  1.57100000e+03   1.57079637e+00]]    
 [[  6.68000000e+02   1.57079637e+00]]    
 [[  5.46000000e+02   1.57079637e+00]]    
 [[  1.42700000e+03   1.57079637e+00]]
 ...
 [[  1.49100000e+03   1.57079637e+00]]]

请注意，这是一个3D数组，而示例代码将其视为2D数组。修复只是从3D数组中提取rho和theta（只改变前两行）：

for line in lines:
    rho, theta = line[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))

    cv2.line(img,(x1,y1),(x2,y2),(0,0,255),2)