extern "C" _declspec(dllexport) void Getmat(uchar *data,size_t &size)

{

	vector<uchar>buf;

	Mat img = imread("D:\\1.jpg");//读入图片

	imencode(".bmp", img, buf);   //将Mat以BMP格式存入uchar的buf数组中

	size = buf.size();

	for each(uchar var in buf)    //将buf拷贝到C#的byte[]中

	{

  *data = var;

  data++;

	}

}

[DllImport("mydll.dll")]

public static extern void Getmat(ref byte data,out ulong size);

  
public Form1()

        {

            InitializeComponent();

            byte[] imgdata = new byte[3200 * 2400 * 3];//存储图片的数组，必须大于等于图片分辨率

            ulong size = new ulong();

            Getmat(ref imgdata[0], out size);

            pictureBox1.Image = Image.FromStream(new MemoryStream(imgdata, 0, (int)size));

        }