emgu 画出了矩形，怎么截图并显示

Question

for (int i = 0; i < faces.Length; ++i)
{
var obj = faces[i];
rect = new System.Drawing.Rectangle(obj.rect.x, obj.rect.y, obj.rect.width, obj.rect.height);
rect.Inflate(50, 100);
Emgu.CV.CvInvoke.Rectangle(mat, rect, new Emgu.CV.Structure.MCvScalar(0, 255, 0), 3);
Emgu.CV.CvInvoke.PutText(mat, string.Format("F{0}/{1:N2}", i + 1, obj.score),
new System.Drawing.Point(obj.rect.x, obj.rect.y),
Emgu.CV.CvEnum.FontFace.HersheyComplex, 0.5, new Emgu.CV.Structure.MCvScalar(0, 0, 255));

                            foreach (var pt in obj.landmark)
                            {
                                Emgu.CV.CvInvoke.Circle(mat, new System.Drawing.Point(pt.x, pt.y), 3, new Emgu.CV.Structure.MCvScalar(255, 255, 0), 2);
                            }
                        }