窗口8中出现捕获图像错误

我有一个用来捕获屏幕的类

class ScreenCapture
{
    public Image CaptureScreen()
    {
        return CaptureWindow(User32.GetDesktopWindow());
    }
    /// <summary>
    /// Creates an Image object containing a screen shot of a specific window
    /// </summary>
    /// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
    /// <returns></returns>
    public Image CaptureWindow(IntPtr handle)
    {
        // get the hDC of the target window
        IntPtr hdcSrc = User32.GetWindowDC(handle);
        // get the size
        User32.RECT windowRect = new User32.RECT();
        User32.GetWindowRect(handle, ref windowRect);
        int width = windowRect.right - windowRect.left;
        int height = windowRect.bottom - windowRect.top;
        // create a device context we can copy to
        IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
        // create a bitmap we can copy it to,
        // using GetDeviceCaps to get the width/height
        IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
        // select the bitmap object
        IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
        // bitblt over
        GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
        // restore selection
        GDI32.SelectObject(hdcDest, hOld);
        // clean up 
        GDI32.DeleteDC(hdcDest);
        User32.ReleaseDC(handle, hdcSrc);
        // get a .NET image object for it
        Image img = Image.FromHbitmap(hBitmap);
        // free up the Bitmap object
        GDI32.DeleteObject(hBitmap);
        return img;
    }
    /// <summary>
    /// Captures a screen shot of a specific window, and saves it to a file
    /// </summary>
    /// <param name="handle"></param>
    /// <param name="filename"></param>
    /// <param name="format"></param>
    public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
    {
        Image img = CaptureWindow(handle);
        img.Save(filename, format);
    }
    /// <summary>
    /// Captures a screen shot of the entire desktop, and saves it to a file
    /// </summary>
    /// <param name="filename"></param>
    /// <param name="format"></param>
    public void CaptureScreenToFile(string filename, ImageFormat format)
    {
        Image img = CaptureScreen();
        img.Save(filename, format);
    }
    /// <summary>
    /// Resize a bitmap image
    /// </summary>
    /// <param name="bmp">Bitmap File</param>
    /// <param name="nWidth">new width</param>
    /// <param name="nHeight">new height</param>
    /// <returns>return a new bitmap image after resizing</returns>
    public Bitmap ResizeBitmap(Bitmap bmp, int nWidth, int nHeight)
    {
        Bitmap resultBmp = new Bitmap(nWidth, nHeight);
        using (Graphics g = Graphics.FromImage((Image)resultBmp))
        {
            g.InterpolationMode = InterpolationMode.NearestNeighbor;
            g.DrawImage(bmp, 0, 0, nWidth, nHeight);
        }
        return resultBmp;
    }
    /// <summary>
    /// Helper class containing Gdi32 API functions
    /// </summary>
    private class GDI32
    {
        public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
        [DllImport("gdi32.dll")]
        public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
            int nWidth, int nHeight, IntPtr hObjectSource,
            int nXSrc, int nYSrc, int dwRop);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
            int nHeight);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
    }
    /// <summary>
    /// Helper class containing User32 API functions
    /// </summary>
    private class User32
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }
        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(IntPtr hWnd);
        [DllImport("user32.dll")]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
    }
}

然后我声明一个变量并捕获屏幕并将其保存到图像

   private ScreenCapture m_handleCapture = new ScreenCapture();
   m_handleCapture.CaptureScreenToFile("C:''temp2.gif", ImageFormat.Gif);

图像未满，右侧和底部区域被裁剪。我不知道为什么。该代码在窗口8上运行，64位。