c++ - OpenCV C++ : Sorting contours by their contourArea

Question

如何根据等高线区域的大小对等高线进行排序？我怎样才能得到最大/最小的？

Answer 1

您可以使用 std::sort使用自定义比较函数对象

// comparison function object
bool compareContourAreas ( std::vector<cv::Point> contour1, std::vector<cv::Point> contour2 ) {
    double i = fabs( contourArea(cv::Mat(contour1)) );
    double j = fabs( contourArea(cv::Mat(contour2)) );
    return ( i < j );
}

用法:

[...]

// find contours
std::vector<std::vector<cv::Point> > contours;
std::vector<cv::Vec4i> hierarchy;
cv::findContours( binary_image, contours, hierarchy, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE, cv::Point(0, 0) );

// sort contours
std::sort(contours.begin(), contours.end(), compareContourAreas);

// grab contours
std::vector<cv::Point> biggestContour = contours[contours.size()-1];
std::vector<cv::Point> smallestContour = contours[0];