Opencv寻找轮廓的最小外接矩形，并获取矩形的中心点，旋转角度

本代码可用于获取物体的坐标偏移量，旋转角度。

                //if(thresholdValue)                {                    Mat src  = Mat(imHeight,imWidth,CV_8U,pImageBuffer);                    Mat mat;                    src.copyTo(mat);                    threshold(mat,mat,thresholdValue,1,CV_THRESH_BINARY);                    //寻找最外层轮廓                    vector<vector<Point>> contours;                    vector<Vec4i> hierarchy;                    findContours(mat,contours,hierarchy,RETR_EXTERNAL,CHAIN_APPROX_NONE,Point());                    Mat imageContours=Mat::zeros(mat.size(),CV_8UC1); //最小外接矩形画布                    int toatal = 0;                    int index = 0;                    for(int i=0;i<contours.size();i++)                    {                        int  length = contours[i].size();                        if(length > 5000)                        {                            index = i;                            toatal++;                            //绘制轮廓                            //drawContours(src,contours,i,Scalar(255),1,8,hierarchy);                            //绘制轮廓的最小外结矩形                            RotatedRect rect=minAreaRect(contours[i]);                            Point2f P[4];                            rect.points(P);                            for(int j=0;j<=3;j++)                            {                                line(src,P[j],P[(j+1)%4],Scalar(255),2);                            }                            double x0,y0,alpha;                            x0 = rect.center.x;                    //  中心位置                            y0 = rect.center.y;                            alpha = -rect.angle*CV_PI/180;         //  角度转换成弧度                            int w =20;//十字叉的宽度                                                  //绘制轮廓的中心                            line(src,Point2f(x0-w,y0),Point2f(x0+w,y0),Scalar(0),2);                            line(src,Point2f(x0,y0-w),Point2f(x0,y0+w),Scalar(0),2);                            //绘制图像的中心                            line(src,Point2f(imWidth/2-w,imHeight/2),Point2f(imWidth/2+w,imHeight/2),Scalar(0),2);                            line(src,Point2f(imWidth/2,imHeight/2-w),Point2f(imWidth/2,imHeight/2+w),Scalar(0),2);                            double x_offset,  y_offset,  angle;                            x_offset = x0-imWidth/2;                            y_offset = y0-imHeight/2;                            angle = -rect.angle*CV_PI/180;                            //emit SendRectInfo(x_offset, y_offset, angle, length);                        }                    }                }