Communication between opencv c ++ and Unity3D

I have a problem that I hope you can help me solve:

I have to try to pass a cv :: Mat from c ++ to C # to convert it into a Texture2D. That is, I from c ++ capture the image of my Webcam using opencv. Once I have obtained the frame in cv :: Mat format, I have to pass it to C # to be able to show it in a Texture2D. The problem is that I do not get that communication. I add the code so you can advise me. Greetings and thanks

C ++:

__declspec(dllexport)
void video(unsigned char  *ptr, int wid, int high)
{
    VideoCapture camera;
    if (!camera.open(0))
    {
        return;
    }
    Mat frame;
    camera >> frame;
    if (!frame.empty())
    {
        ptr = frame.data;
        wid = frame.cols;
        high = frame.rows;
        imshow("CAMARA", frame);
    }
}

Unity C #

[DllImport("NativoPrincipio.dll")]public static extern void video(out IntPtr Image, out int wid, out int hig);
            IntPtr im_ptr = IntPtr.Zero;
            webcamTexture.Stop();
            int wid = webcamTexture.width;
            int hei = webcamTexture.height;
            video(out im_ptr, out wid, out hei);
            //byte* src = (byte*)im_ptr.ToPointer();
            Texture2D tex = Texture2D.CreateExternalTexture(wid, hei, TextureFormat.RGB24, false, false, im_ptr);
            File.WriteAllBytes("C:\Users\usortiz\Desktop\pepe.png", (byte[])tex.EncodeToPNG());
            GetComponent<Renderer>().material.mainTexture = tex;