[ORB_SLAM2] void Frame::ComputeImageBounds(const cv::Mat & imLeft)

ComputeImageBoundsThe main purpose of this function is to get to the scope of the distortion after image coordinates,For subsequent meshing boundary value,This function will only be in the first frame come in or internal changed is called,Here the boundary value of selected using the maximum coverage criterion,Which is the top left corner in small,The lower right corner to take big,Which can cover the whole to distortion after image

void Frame::ComputeImageBounds(const cv::Mat &imLeft)	
{
    
    // 如果畸变参数不为0,用OpenCV函数进行畸变矫正
    if(mDistCoef.at<float>(0)!=0.0)
	{
    
        // Save the correct image in front of the four boundary point coordinates： (0,0) (cols,0) (0,rows) (cols,rows)
        cv::Mat mat(4,2,CV_32F);
        mat.at<float>(0,0)=0.0;         //左上
		mat.at<float>(0,1)=0.0;
        mat.at<float>(1,0)=imLeft.cols; //右上
		mat.at<float>(1,1)=0.0;
		mat.at<float>(2,0)=0.0;         //左下
		mat.at<float>(2,1)=imLeft.rows;
        mat.at<float>(3,0)=imLeft.cols; //右下
		mat.at<float>(3,1)=imLeft.rows;

        // Undistort corners
		// Operation and calibration feature points in front,Will this a few boundary points as the input for correction
        mat=mat.reshape(2);
        cv::undistortPoints(mat,mat,mK,mDistCoef,cv::Mat(),mK);
        mat=mat.reshape(1);

		//After correction of the four boundary point is not able to round into a rigid rectangular,So add borders as coordinates on the outside of the quadrilateral boundary
        mnMinX = min(mat.at<float>(0,0),mat.at<float>(2,0));//左上和左下横坐标最小的
        mnMaxX = max(mat.at<float>(1,0),mat.at<float>(3,0));//右上和右下横坐标最大的
        mnMinY = min(mat.at<float>(0,1),mat.at<float>(1,1));//左上和右上纵坐标最小的
        mnMaxY = max(mat.at<float>(2,1),mat.at<float>(3,1));//左下和右下纵坐标最小的
    }
    else
    {
    
        // If the distortion parameters as0,Direct access to the image boundary
        mnMinX = 0.0f;
        mnMaxX = imLeft.cols;
        mnMinY = 0.0f;
        mnMaxY = imLeft.rows;
    }
}