python - 在OpenCV Python中画线时出错

Question

所以我想做的是使用霍夫变换在图像上找到线，然后将线绘制到图像中。

但我收到一条错误消息:

Traceback (most recent call last): 
    File "houghLines.py", line 31, in <module>
    main() File "houghLines.py", line 13, in main 
    a = hough(image)
    File "houghLines.py", line 29, in hough
    (0,0,255))
    TypeError: only length-1 arrays can be converted to Python scalars

这是我的代码:

import cv2
import os
import math
def main():

    directory = os.path.dirname(__file__)
    picLoc = os.path.join(directory, "../video-image/1m50s.png")

    image = cv2.imread(picLoc)
    print "sending image to houghLines.py"

    a = hough(image)
    cv2.imshow("", a)
    cv2.waitKey(0)
    cv2.destroyAllChildren()

def hough(image):
    canny = cv2.Canny(image, 50, 200)
    color_image = cv2.cvtColor(canny, cv2.COLOR_GRAY2BGR)
    houghLines = cv2.HoughLinesP(canny, 1, math.pi/180, 50)
    for x in range(len(houghLines)):
        print x
        pt1 = (houghLines[x][0], houghLines[x][1])
        pt2 = (houghLines[x][2], houghLines[x][3])
        cv2.line(color_image, pt1, pt2, (0,0,255), 3)
    return color_image

main()

Answer 1

发生此问题的原因是cv2.line()期望pt1和pt2为仅由单个元素组成的元组，每个x和y坐标。如果在示例中使用print pt1，您将很快发现情况并非如此。
cv2.HoughLinesP()返回仅包含一个元素的numpy数组。此元素包含四个点的列表，它们是行的起点和终点。知道这一点，正确的实现如下:

    for line in houghLines[0]:
        pt1 = tuple(line[:2])
        print pt1
        pt2 = tuple(line[-2:])
        cv2.line(color_image, pt1, pt2, (0,0,255), 3)