emgu 图像列获取

public Form1()
        {
           
            InitializeComponent();

            Image<Gray, byte> src = new Image<Gray, byte>("b.png");  //读取图片并进行灰度化处理
            Image<Gray, byte> submat = new Image<Gray, byte>(src.Width, 1); 
            CvInvoke.cvGetCol(src, submat, 30);//获取图像的某一列  
            imageBox2.Image = submat ;

        }