OpenCV 应用fitEllipse函数一种异常问题分析

末蓝、 2022-07-13 09:10 123阅读 0赞

想要求得一个图像中轮廓的椭圆拟合 代码如下：

for(int k = 0; k < (int)threecontours.size(); k++)   
          { 
    RotatedRect rRect = fitEllipse(threecontours.at(k)); 
    double majorAxis = rRect.size.height > rRect.size.width ? rRect.size.height : rRect.size.width;
    double minorAxis = rRect.size.height > rRect.size.width ? rRect.size.width : rRect.size.height;
    float rate = majorAxis/minorAxis;
        if (rate<2)   //滤除长短轴小于2的轮廓
        {
        drawContours(g_EllipseFilter, threecontours, k, Scalar(0), CV_FILLED);
    }
    
    }

处理部分图片时发现异常：  
![这里写图片描述][3a65b340fb738459ac995bc438cd9c10.png]  
调试程序时发现：某个轮廓内的像素点个数只有四个  
![这里写图片描述][4c35cea0199aa7dad4b25ca13aa8e8e2.png]  
说明fitEllipse函数要求轮廓的像素点个数大于等于5个，可以将代码修改为：

for(int k = 0; k < (int)threecontours.size(); k++)    //查找轮廓
          {
    if (int(threecontours.at(k).size()) <=6)
    {
    drawContours(g_EllipseFilter, threecontours, k, Scalar(0), CV_FILLED);
    }
    else
    {
    RotatedRect rRect = fitEllipse(threecontours.at(k)); 
    double majorAxis = rRect.size.height > rRect.size.width ? rRect.size.height : rRect.size.width;
    double minorAxis = rRect.size.height > rRect.size.width ? rRect.size.width : rRect.size.height;
    float rate = majorAxis/minorAxis;
                    if (rate<2)   //滤除长短轴小于2的轮廓
                {
        drawContours(g_EllipseFilter, threecontours, k, Scalar(0), CV_FILLED);
            }
    }
    
    }

[3a65b340fb738459ac995bc438cd9c10.png]: /images/20220713/a0e4972e39ea43918538f1e2b03df648.png
[4c35cea0199aa7dad4b25ca13aa8e8e2.png]: /images/20220713/ba524e16a4ce4c8298f9eef5a5fe43f4.png