Capture image error in window 8

Question

I have a class that I'm using to capture Screen

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);

    }
}

And then I declare a variable and capture screen and save it to an image

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

The image is not full, right and bottom regions are cropped. I don't know why. The code was running on window 8, 64 bit.

Answer 1

An alternative is applying this answer. It give you full information about how to get DPI, and some problem about it.

How to get Windows Display settings?

Answer 2

To receive the physical (opposed to the logical) size of the target HWND, mark your application as High DPI aware, or use LogicalToPhysicalPointForPerMonitorDPI to translate the result from GetWindowRect.

To mark your application as High DPI aware, add the following to your manifest:

<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0" xmlns:asmv3="urn:schemas-microsoft-com:asm.v3" >
  <asmv3:application>
    <asmv3:windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
      <dpiAware>true</dpiAware>
    </asmv3:windowsSettings>
  </asmv3:application>
</assembly>

See MSDN: Accessing Window Trees while System DPI–aware for details on High DPI support.

Answer 3

An alternative is to convert the width\height to 96dpi for the image.

double dpiX, dpiY;
double width, height;

int dpi96Width = (int)(width/dpiX * 96);
int dpi96Height = (int)(height/dpiY * 96);

See here for more info on DPI-aware applications.

Answer 4

Just change DPI to the smallest. It works.

Here taught me how to change: http://acer.custhelp.com/app/answers/detail/a_id/10807/~/how-do-i-change-the-dpi-of-my-display-on-my-computer-with-windows-7%3F