如何检查点是否放置在轮廓内? [英] How to check if point is placed inside contour?

问题描述

我已在极端点周围绘制了轮廓.在多边形图中，我还有其他要点. 如何检查它们是否在轮廓内?

I have drawn a contour around extreme points. Inside polygon figure I have others points. How to check if they are inside contour?

推荐答案

您可以使用OpenCV中可用的cv2.pointPolygonTest()函数.

You can use the cv2.pointPolygonTest() function available in OpenCV.

例如:

dist = cv2.pointPolygonTest(cnt,(50,50),True)

在此示例中，我们正在检查是否在轮廓cnt中出现坐标(50, 50)

In this example we are checking whether the coordinate (50, 50) is present withing the contour cnt

1. dist返回以下三个之一:

如果点在轮廓的内部内，则为
• 正值值
如果点在轮廓的外部之外，则
• 负值
• 归零(如果该点位于轮廓上 上
)

• Positive value if the point is inside the contour
• Negative value if the point is outside the contour
• Zero if the point is on the contour

在函数cv2.pointPolygonTest()中，第三个参数决定是否要以下两个之一:

Within the function cv2.pointPolygonTest() the third parameter decides whether you want one of the following two :

• 如果它是 True ，则dist返回该点的正或负距离(如果该点分别在轮廓的内部或外部).
• 另一方面，如果将其设置为 False ，则根据分别位于内部，外部或轮廓上的点，它会返回+ 1，-1或0.

• If it is True, dist returns either the positive or negative distance of the point, if it is either inside or outside the contour respectively.
• On the other hand, if it is set to False, it returns +1, -1 or 0 depending on the point lying inside, outside or on the contour respectively

有关更多详细信息，请参见 DOCS

See THE DOCS for more details

我添加了一个示例来演示其工作原理.我考虑了以下获得轮廓的图像:

I added an example to show how it works. I considered the following image for which a contour was obtained:

我假设要使用以下几点进行说明:

I assumed the following points to be used as illustration:

(50, 70), (170, 152), (152, 48)

dist1 = cv2.pointPolygonTest(contours[0], (50, 70), True)
dist2 = cv2.pointPolygonTest(contours[0], (170, 152), True)
dist3 = cv2.pointPolygonTest(contours[0], (152, 48), True)

print('dist1 : ', dist1)
print('dist2 : ', dist2)
print('dist3 : ', dist3)

输出:

('dist1 : ', -45.17742799230607)
('dist2 : ', 49.9799959983992)
('dist3 : ', -0.0)

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