PrintWindow Flickering

Question

I'm trying to capture a window using the method I always used with PrintWindow

RECT rc;
GetClientRect(hwnd, out rc); //The process window handler

Bitmap bmp = new Bitmap(rc.right, rc.bottom, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
Graphics gfxBmp = Graphics.FromImage(bmp);
IntPtr hdcBitmap = gfxBmp.GetHdc();

PrintWindow(hwnd, hdcBitmap, 1);

gfxBmp.ReleaseHdc(hdcBitmap);
gfxBmp.Dispose();
bmp.Save("test.png");

The problem is that in this specific game process the window gets blank really fast when it calls the Printwindow function, so sometimes the image saved is totally white.

So I tried to use BitBlt:

Bitmap bmp = new Bitmap(rc.right, rc.bottom, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
Graphics gfxBmp = Graphics.FromImage(bmp);
IntPtr dest = gfxBmp.GetHdc();
IntPtr source = GetWindowDC(hwnd);

BitBlt(dest, 0, 0, rc.width, rc.height, source, 0, 0, 13369376);
bmp.Save("test.png");

But using the code above the image saved is totally black.

There is any way to prevent PrintWindow to make the process window to flick that "white layer" ? If it's nto possible BitBtl should solve that issue for me right? But what is wrong with my code?

Thank you

Answer 1

You could try with this code, it's working for me. If you still see black image, probably you have to go for DWM solution.

UPDATE: fixed missing window argument

    public Bitmap CaptureWindowImage(IntPtr hWnd, System.Drawing.Rectangle wndRect)
    {
        IntPtr hWndDc = GetDC(hWnd);
        IntPtr hMemDc = CreateCompatibleDC(hWndDc);
        IntPtr hBitmap = CreateCompatibleBitmap(hWndDc, wndRect.Width, wndRect.Height);
        SelectObject(hMemDc, hBitmap);

        BitBlt(hMemDc, 0, 0, wndRect.Width, wndRect.Height, hWndDc, 0, 0, TernaryRasterOperations.SRCCOPY);
        Bitmap bitmap = Bitmap.FromHbitmap(hBitmap);

        DeleteObject(hBitmap);
        ReleaseDC(hWnd, hWndDc);
        ReleaseDC(IntPtr.Zero, hMemDc);

        return bitmap;
    }

    private enum TernaryRasterOperations : uint
    {
        /// <summary>dest = source</summary>
        SRCCOPY = 0x00CC0020,
        /// <summary>dest = source OR dest</summary>
        SRCPAINT = 0x00EE0086,
        /// <summary>dest = source AND dest</summary>
        SRCAND = 0x008800C6,
        /// <summary>dest = source XOR dest</summary>
        SRCINVERT = 0x00660046,
        /// <summary>dest = source AND (NOT dest)</summary>
        SRCERASE = 0x00440328,
        /// <summary>dest = (NOT source)</summary>
        NOTSRCCOPY = 0x00330008,
        /// <summary>dest = (NOT src) AND (NOT dest)</summary>
        NOTSRCERASE = 0x001100A6,
        /// <summary>dest = (source AND pattern)</summary>
        MERGECOPY = 0x00C000CA,
        /// <summary>dest = (NOT source) OR dest</summary>
        MERGEPAINT = 0x00BB0226,
        /// <summary>dest = pattern</summary>
        PATCOPY = 0x00F00021,
        /// <summary>dest = DPSnoo</summary>
        PATPAINT = 0x00FB0A09,
        /// <summary>dest = pattern XOR dest</summary>
        PATINVERT = 0x005A0049,
        /// <summary>dest = (NOT dest)</summary>
        DSTINVERT = 0x00550009,
        /// <summary>dest = BLACK</summary>
        BLACKNESS = 0x00000042,
        /// <summary>dest = WHITE</summary>
        WHITENESS = 0x00FF0062
    }

    [DllImport("gdi32.dll", ExactSpelling = true, PreserveSig = true, SetLastError = true)]
    static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);

    [DllImport("gdi32.dll", SetLastError = true)]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll")]
    private static extern bool DeleteObject(IntPtr hObject);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateBitmap(int nWidth, int nHeight, uint cPlanes, uint cBitsPerPel, IntPtr lpvBits);

    [DllImport("user32.dll")]
    private static extern IntPtr GetDC(IntPtr hWnd);

    [DllImport("user32.dll")]
    private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

    [DllImport("gdi32.dll")]
    private static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);