首先貼一個最簡單的程序：訪問：https://blog.csdn.net/guduruyu/article/details/70069426

//創建一個用于繪制圖像的空白圖    
cv::Mat image = cv::Mat::ones(480, 640, CV_8UC3);  
//設置藍色背景  
image.setTo(cv::Scalar(100, 0, 0));  //輸入擬合點    
std::vector<cv::Point> points;  points.push_back(cv::Point(200, 240));  
points.push_back(cv::Point(300, 400));  
points.push_back(cv::Point(400, 360));  
points.push_back(cv::Point(500, 300));  
points.push_back(cv::Point(500, 200));  
points.push_back(cv::Point(300, 150));  //將擬合點繪制到空白圖上    
for (int i = 0; i < points.size(); i++)  
{  cv::circle(image, points[i], 5, cv::Scalar(0, 0, 255), 2, 8, 0);  
}  //獲取擬合橢圓的外包圍矩形  
cv::RotatedRect rotate_rect = cv::fitEllipse(points);  
//繪制擬合橢圓  
cv::ellipse(image, rotate_rect, cv::Scalar(0, 255, 255), 2, 8);  cv::imshow("image", image);  
cv::waitKey(0);  

其次，這里有關于opencv橢圓擬合的各種定義：https://blog.csdn.net/suky520/article/details/18601307

opencv中的橢圓通過RotatedRect來定義，其center(塊中心(x,y)), size(寬和高,寬小于高), angle（旋轉角）分別對應橢圓的中心，短軸和長軸，旋轉角度。?

         RotatedRect box = fitEllipse(pointsf);  //把那些長軸與短軸之比很多的那些橢圓剔除。  if( MAX(box.size.width, box.size.height) > MIN(box.size.width, box.size.height)*8 )  continue;  //繪制輪廓  drawContours(cimage, contours, (int)i, Scalar::all(255), 1, 8);  //繪制橢圓  ellipse(cimage, box, Scalar(0,0,255), 1, CV_AA);  //繪制橢圓  // ellipse(cimage, box.center, box.size*0.5f, box.angle, 0, 360, Scalar(0,255,255), 1, CV_AA);  //注意這里需要乘以0.5

最后，目前opencv3中支持三種橢圓擬合方式：fitEllipse，fitEllipseAMS，fitEllipseDirect，其中第三種來自《 Direct least squares fitting of ellipsees, Fitzgibbon, Pilu and Fischer in Fitzgibbon, A.W., Pilu, M., and Fischer R.B.,Proc. of the 13th Internation Conference on Pattern Recognition, pp 253–257, Vienna, 1996》

可以訪問https://docs.opencv.org/trunk/de/dc7/fitellipse_8cpp-example.html

來看官方的橢圓擬合事例。?

參考鏈接：

1.?https://blog.csdn.net/suky520/article/details/18601307

2.?https://www.cnblogs.com/as3asddd/p/7455712.html

3. https://blog.csdn.net/u012566751/article/details/54345465?

4.?https://blog.csdn.net/guduruyu/article/details/70069426