如何将GDI绘制图片存入硬盘

 private void button1_Click(object sender, EventArgs e)
        {
            Bitmap bitMap = new Bitmap(1203, 941);
            Bitmap bitMapOrg = (Bitmap)Bitmap.FromFile("D:\\zp\\螺栓位置信息.jpg");

            IntPtr intPtrBitMap = IntPtr.Zero;
            Graphics grapDes = Graphics.FromImage(bitMap);
           // Graphics graphicsControl = Graphics.FromImage(bitMapOrg);
            IntPtr hdc = grapDes.GetHdc();
            IntPtr intPtrControlMemary = Gdi32.CreateCompatibleDC(hdc);
            intPtrBitMap = bitMapOrg.GetHbitmap();
            Gdi32.SelectObject(intPtrControlMemary, intPtrBitMap);

            //可在贴图前绘制标定点信息
            Gdi32.BitBlt(hdc, 100 , 100, 1203 , 941 , intPtrControlMemary, 0 , 0  , Gdi32.TernaryRasterOperations.SRCCOPY );

            Gdi32.DeleteObject(intPtrBitMap);
            grapDes.ReleaseHdc(hdc);
            Gdi32.DeleteDC(intPtrControlMemary);
            grapDes.Dispose();
            //graphicsControl.Dispose();
            if (System.IO.File.Exists("d:\\1234444.jpg"))
                System.IO.File.Delete("d:\\1234444.jpg");

            bitMap.Save("d:\\1234444.jpg" ,System.Drawing.Imaging.ImageFormat.Jpeg);

            bitMap.Dispose();
            bitMapOrg.Dispose();
        }