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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);
 
            // 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;
        }
 
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, CopyPixelOperation rop);
 
            [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);
        }
    }
}
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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