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Hello, I'm currently trying to capture a fullscreen game with antialiasing mode activated via BitBlt, but it returns a black screenshot. If I disable the antialiasing, the screenshot works perfectly.

Any ideas?

Here's the code I'm using:
 
public Image CaptureWindow(IntPtr handle)
        {
            // get the DC of the target window
            IntPtr hdcSrc = User32.GetWindowDC(handle);
 
<pre>
        // 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, CopyPixelOperation.SourceCopy | CopyPixelOperation.CaptureBlt);
 
        // 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;
    }</pre>
 
private class GDI32
        {
 
<pre>
        //public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter

        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
            int nWidth, int nHeight, IntPtr hObjectSource,
            int nXSrc, int nYSrc, CopyPixelOperation rop);
 
        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
            int nHeight);
 
        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
 
        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern bool DeleteDC(IntPtr hDC);
 
        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern bool DeleteObject(IntPtr hObject);
 
        [DllImport(&quot;gdi32.dll&quot;)]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
    }
 
    /// &lt;summary&gt;
    /// Helper class containing User32 API functions
    /// &lt;/summary&gt;

    private class User32
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }
 
        [DllImport(&quot;user32.dll&quot;)]
        public static extern IntPtr GetDesktopWindow();
 
        [DllImport(&quot;user32.dll&quot;)]
        public static extern IntPtr GetWindowDC(IntPtr hWnd);
 
        [DllImport(&quot;user32.dll&quot;)]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
 
        [DllImport(&quot;user32.dll&quot;)]
        public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
    }
}

}
Posted 16-Jun-13 9:39am

1 solution

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Solution 1

There is absolutely no need to use P/Invoke with your Forms application. All you need from GDI+ is available in System.Drawing:
http://msdn.microsoft.com/en-us/library/system.drawing.aspx[^].

—SA

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