C# 非活动窗口截屏

 public class CaptureWindows
    {

        public static Bitmap GetWindow(IntPtr hWnd)
        {
            IntPtr hscrdc = GetWindowDC(hWnd);
            Rectangle rect = new Rectangle();
            GetWindowRect(hWnd, out rect);
            IntPtr hbitmap = CreateCompatibleBitmap(hscrdc, rect.Width - rect.X, rect.Height - rect.Y);
            IntPtr hmemdc = CreateCompatibleDC(hscrdc);
            SelectObject(hmemdc, hbitmap);
            PrintWindow(hWnd, hmemdc, 0);
            Bitmap bmp = Bitmap.FromHbitmap(hbitmap);
            DeleteDC(hscrdc);
            DeleteDC(hmemdc);
            return bmp;
        }



        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateDC(
         string lpszDriver,        // driver name
         string lpszDevice,        // device name
         string lpszOutput,        // not used; should be NULL
         IntPtr lpInitData  // optional printer data
         );
        [DllImport("gdi32.dll")]
        public static extern int BitBlt(
         IntPtr hdcDest, // handle to destination DC
         int nXDest,  // x-coord of destination upper-left corner
         int nYDest,  // y-coord of destination upper-left corner
         int nWidth,  // width of destination rectangle
         int nHeight, // height of destination rectangle
         IntPtr hdcSrc,  // handle to source DC
         int nXSrc,   // x-coordinate of source upper-left corner
         int nYSrc,   // y-coordinate of source upper-left corner
         UInt32 dwRop  // raster operation code
         );

        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(
         IntPtr hdc // handle to DC
         );

        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(
         IntPtr hdc,        // handle to DC
         int nWidth,     // width of bitmap, in pixels
         int nHeight     // height of bitmap, in pixels
         );

        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(
         IntPtr hdc,          // handle to DC
         IntPtr hgdiobj   // handle to object
         );

        [DllImport("gdi32.dll")]
        public static extern int DeleteDC(
         IntPtr hdc          // handle to DC
         );

        [DllImport("user32.dll")]
        public static extern bool PrintWindow(
         IntPtr hwnd,               // Window to copy,Handle to the window that will be copied. 
         IntPtr hdcBlt,             // HDC to print into,Handle to the device context. 
         UInt32 nFlags              // Optional flags,Specifies the drawing options. It can be one of the following values. 
         );

        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(
         IntPtr hwnd
         );

        [DllImport("user32.dll", EntryPoint = "GetWindowRect")]
        private static extern int GetWindowRect(IntPtr hwnd, out   Rectangle lpRect);
    }