使用gdi+实时绘制picturebox（画个叉）

private void DrawReticle(System.Drawing.Point pt, int size)//画一个透明的前景图片上画十字

{

Bitmap bmp = new Bitmap(imageWindows[2].Width, imageWindows[2].Height);//用图片大小不要用控件大小

Graphics g = Graphics.FromImage(bmp);

g.Clear(Color.Transparent);

Pen MyPen = new Pen(Color.Red, 1);

System.Drawing.Point pt1 = new System.Drawing.Point(pt.X - size, pt.Y);

System.Drawing.Point pt2 = new System.Drawing.Point(pt.X + size, pt.Y);

System.Drawing.Point pt3 = new System.Drawing.Point(pt.X, pt.Y - size);

System.Drawing.Point pt4 = new System.Drawing.Point(pt.X, pt.Y + size);

//使用DrawLine方法绘制直线

g.DrawLine(MyPen, pt1, pt2);

g.DrawLine(MyPen, pt3, pt4);

g.Dispose();

imageWindows[2].Image = bmp；

}

private void RealTimeGrab()

{

while (true)

{

if (isOpen)

{

System.Drawing.Point pt1 = new System.Drawing.Point(int.Parse(nudXCoord.Text), int.Parse(nudYCoord.Text));

DrawReticle(pt1, int.Parse(nudReticleSize.Text));

}

imageWindows[2].BeginInvoke(new Action(() =>

{

imageWindows[2].BackgroundImage = dst;//给背景图赋值 Bitmap dst

}));

                    }
            }