获取包围对象的多边形 approxPolyDP

// testing the approximate polygon
std::vector<cv::Point> poly;
cv::approxPolyDP(cv::Mat(contours[2]),poly,
5, // accuracy of the approximation
true); // yes it is a closed shape

1. // 轮廓表示为一个多边形 
2. vector<Point> poly; 
3. approxPolyDP(Mat(contours[2]), poly, 5, true); 
4. vector<Point>::const_iterator itp = poly.begin(); 
5. while (itp != (poly.end() - 1)) 
6. { 
7.     line(result, *itp, *(itp + 1), Scalar(255), 2); 
8.     ++itp; 
9. } 
10. line(result, *itp, *(poly.begin()), Scalar(255), 2);