使用cv2.pointPolygonTest（）和cv2.polylines（）的问题

Question

我正在尝试绘制形状，然后检查该点是否在形状内。想到使用cv2.polylines()进行绘制并使用cv2.pointPolygonTest()进行测试应该可以工作，但会得到一个错误消息，该错误消息的内容不是很丰富。

Traceback (most recent call last):
  File "C:\Users\XXX\Desktop\Heatmap\cvtest.py", line 32, in <module>
    dist = cv2.pointPolygonTest(cv2.polylines(img,[pts],True,(0, 255 , 0), 2), (52,288), False)
cv2.error: OpenCV(4.1.0) C:\projects\opencv-python\opencv\modules\imgproc\src\geometry.cpp:103: error: (-215:Assertion failed) total >= 0 && (depth == CV_32S || depth == CV_32F) in function 'cv::pointPolygonTest'

我猜测用cv2.polylines()创建的形状不是轮廓。那么正确的方法是什么？我当前的代码：

import cv2
import numpy as np

img = cv2.imread('image.png')

pts = np.array([[18,306],[50,268],[79,294],[165,328],[253,294],[281,268],[313,306],[281,334],[270,341],[251,351],[230,360],[200,368],[165,371],[130,368],[100,360],[79,351],[50,334],[35,323]], np.int32)
pts = pts.reshape((-1,1,2))

dist = cv2.pointPolygonTest(cv2.polylines(img,[pts],True,(0, 255 , 0), 2), (52,288), False)
#print(dist)

cv2.imshow('test', img)
cv2.waitKey()
cv2.destroyAllWindows()

Answer 1

polylines不是正确的输入，它用于绘制形状（docs）
pointPolygonTest相反需要轮廓作为输入（docs）

dist = cv2.pointPolygonTest(pts, (52,288), False)将返回1.0，即轮廓内。

请注意，您可以在没有图像的情况下执行pointPolygonTest。但是，如果要绘制结果，则可以将此代码用作入门工具：

    import cv2
    import numpy as np

    #create background
    img = np.zeros((400,400),dtype=np.uint8)
    # define shape
    pts = np.array([[18,306],[50,268],[79,294],[165,328],[253,294],[281,268],[313,306],[281,334],[270,341],[251,351],[230,360],[200,368],[165,371],[130,368],[100,360],[79,351],[50,334],[35,323]], np.int32)
    pts = pts.reshape((-1,1,2))
    # draw shape
    cv2.polylines(img,[pts],True,(255), 2)
    # draw point of interest
    cv2.circle(img,(52,288),1,(127),3)
    # perform pointPolygonTest
    dist = cv2.pointPolygonTest(pts, (52,288), False)
    print(dist)
    # show image
    cv2.imshow('test', img)
    cv2.waitKey()
    cv2.destroyAllWindows()

结果：