關於C# opencv的WarpPerspective函數的問題

這是我的代碼

private void button3_Click(object sender, EventArgs e)
        {
            Mat img = Cv2.ImRead("P1050219.JPG");
            List<Point2f> pts1 = new List<Point2f>();
            pts1.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));
            IEnumerable<Point2f> pts11 = pts1 as IEnumerable<Point2f>;
            List<Point2f> pts2 = new List<Point2f>();
            pts2.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));
            IEnumerable<Point2f> pts22 = pts1 as IEnumerable<Point2f>;                    
            Mat M = Cv2.GetPerspectiveTransform( pts1, pts2);
            Mat dst = null;
            OpenCvSharp.Size q = new OpenCvSharp.Size(750,1000);
            Cv2.WarpPerspective(img, dst, M, q, InterpolationFlags.Linear, BorderTypes.Constant);
            this.pictureBox.Show();
            this.pictureBox.Image =  dst.ToBitmap();
        }

運行後報錯，不知道咋改，求大神解答。