opencv 函数pointPolygonTest 检测一个点是否在多边形内

opencv函数

pointPolygonTest：

C++: double pointPolygonTest(InputArray contour, Point2f pt, bool measureDist)

Performs a point-in-contour test.

C++: double pointPolygonTest(InputArray contour, Point2f pt, bool measureDist)

Python: cv2.pointPolygonTest(contour, pt, measureDist) → retval

C: double cvPointPolygonTest(const CvArr* contour, CvPoint2D32f pt, int measure_dist)

Python: cv.PointPolygonTest(contour, pt, measure_dist) → float

Parameters:	contour – Input contour. pt – Point tested against the contour. measureDist – If true, the function estimates the signed distance from the point to the nearest contour edge. Otherwise, the function only checks if the point is inside a contour or not.

The function determines whether the point is inside a contour, outside, or lies on an edge (or coincides with a vertex). It returns positive (inside), negative (outside), or zero (on an edge) value, correspondingly. When measureDist=false , the return value is +1, -1, and 0, respectively. Otherwise, the return value is a signed distance between the point and the nearest contour edge.

使用例子如下：

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1. /// 得到轮廓

2. std::vector<std::vector<cv::Point> > contours;

3. std::vector<cv::Vec4i> hierarchy;

4. cv::Mat src; //src为图像

5.  

6. //contours为函数findContours计算得到的轮廓点分布值

7. cv::findContours( src_copy, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE);

8.  

9. // 计算到轮廓的距离

10. cv::Mat raw_dist( src.size(), CV_32FC1 );

11.  

12. for( int j = 0; j < src.rows; j++ ){

13. for( int i = 0; i < src.cols; i++ ){

14. raw_dist.at<float>(j,i) = cv::pointPolygonTest( contours[0], Point2f(i,j), true );

15. }

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