This is my code

 
Private void button3_Click (object sender, EventArgs e) 
{
Mat img=Cv2. ImRead (" P1050219. JPG "); 
ListPts1. Add (new OpenCvSharp. Point (69, 163)); 
Pts1. Add (new OpenCvSharp. Point (704, 62)); 
Pts1. Add (new OpenCvSharp. Point (162, 675)); 
Pts1. Add (new OpenCvSharp. Point (970, 411)); 
IEnumerableListPts2. Add (new OpenCvSharp. Point (0, 1000)); 
Pts2. Add (new OpenCvSharp. Point (0, 0)); 
Pts2. Add (new OpenCvSharp. Point (750, 1000)); 
Pts2. Add (new OpenCvSharp. Point (750, 0)); 
IEnumerableMat M=Cv2 GetPerspectiveTransform (pts1 pts2); 
Mat DST=null; 
OpenCvSharp. Size q=new OpenCvSharp. Size (750100); 
Cv2. WarpPerspective (img, DST, M, q, InterpolationFlags. Linear, BorderTypes. Constant); 
This. The pictureBox. The Show (); 
Enclosing pictureBox. Image=DST. ToBitmap (); 
} 

After the operation error, don't know how to change, a great god answers,

Error, according to the system. Argumentnullexception value cannot be null.
Arg_paramname_name