c#截取后台窗口的图片

c#截取后台窗口的图片，自测可用，据说性能很一般，用用吧

         struct RECT
         {
             public int Left; // x position of upper-left corner
             public int Top; // y position of upper-left corner
             public int Right; // x position of lower-right corner
             public int Bottom; // y position of lower-right corner
         }
         public static Bitmap GetWindow(IntPtr hWnd)
         {
             IntPtr hscrdc = GetWindowDC(hWnd);
             RECT rect = new RECT();
             GetWindowRect(hWnd, out rect);
             IntPtr hbitmap = CreateCompatibleBitmap(hscrdc, rect.Right - rect.Left, rect.Bottom - rect.Top);
             IntPtr hmemdc = CreateCompatibleDC(hscrdc);
             SelectObject(hmemdc, hbitmap);
             PrintWindow(hWnd, hmemdc, );
             Bitmap bmp = Bitmap.FromHbitmap(hbitmap);
             DeleteDC(hscrdc);
             DeleteDC(hmemdc);
             return bmp;
         }

         //API声明

         [DllImport("user32.dll")]
         private static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);

         [DllImport("gdi32.dll")]
         public static extern IntPtr CreateDC(
                     string lpszDriver,        // driver name驱动名
                     string lpszDevice,        // device name设备名
                     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目标设备的句柄
          int nXDest,  // x-coord of destination upper-left corner目标对象的左上角的X坐标
          int nYDest,  // y-coord of destination upper-left corner目标对象的左上角的Y坐标
          int nWidth,  // width of destination rectangle目标对象的矩形宽度
          int nHeight, // height of destination rectangle目标对象的矩形长度
          IntPtr hdcSrc,  // handle to source DC源设备的句柄
          int nXSrc,   // x-coordinate of source upper-left corner源对象的左上角的X坐标
          int nYSrc,   // y-coordinate of source upper-left corner源对象的左上角的Y坐标
          UInt32 dwRop  // raster operation code光栅的操作值
          );

         [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
          );