Get bitmap of hidden window

[Kligham]

Hi,

I have been searching on google to find a way to get a bitmap of a hidden window. I thought I found it, but when tried it, it is only giving me a good image (not a black one), when my window is in front/active, when hidden it give me a black bitmap.

Here is my code:

public const int SRCCOPY = 13369376;
        public const int WM_CLICK = 0x00F5;


        [DllImport("user32.dll", SetLastError = true)]
        internal static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("user32.dll", EntryPoint = "GetDC")]
        internal extern static IntPtr GetDC(IntPtr hWnd);

        [DllImport("gdi32.dll", EntryPoint = "CreateCompatibleDC")]
        internal extern static IntPtr CreateCompatibleDC(IntPtr hdc);

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

        [DllImport("gdi32.dll", EntryPoint = "DeleteDC")]
        internal extern static IntPtr DeleteDC(IntPtr hDc);

        [DllImport("user32.dll", EntryPoint = "ReleaseDC")]
        internal extern static IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDc);

        [DllImport("gdi32.dll", EntryPoint = "BitBlt")]
        internal extern static bool BitBlt(IntPtr hdcDest, int xDest, int yDest, int wDest, int hDest, IntPtr hdcSource, int xSrc, int ySrc, int RasterOp);

        [DllImport("gdi32.dll", EntryPoint = "SelectObject")]
        internal extern static IntPtr SelectObject(IntPtr hdc, IntPtr bmp);

        [DllImport("gdi32.dll", EntryPoint = "DeleteObject")]
        internal extern static IntPtr DeleteObject(IntPtr hDc);

        [DllImport("user32.dll")]
        public static extern int SendMessage(
              int hWnd,      // handle to destination window
              uint Msg,       // message
              long wParam,  // first message parameter
              long lParam   // second message parameter
              );

        static IntPtr hWnd = FindWindow(null, "My programs title");

        public static Bitmap createBitmap()
        {

            Bitmap bmp = null;

            IntPtr hdcFrom = GetDC(hWnd);

            IntPtr hdcTo = CreateCompatibleDC(hdcFrom);

            //X and Y coordinates of window
            int Width = 529;
            int Height = 436;

            IntPtr hBitmap = CreateCompatibleBitmap(hdcFrom, Width, Height);

            if (hBitmap != IntPtr.Zero)
            {
                // adjust and copy
                IntPtr hLocalBitmap = SelectObject(hdcTo, hBitmap);
                BitBlt(hdcTo, 0, 0, Width, Height,
                    hdcFrom, 0, 0, SRCCOPY);
                SelectObject(hdcTo, hLocalBitmap);
                //We delete the memory device context.
                DeleteDC(hdcTo);
                //We release the screen device context.
                ReleaseDC(hWnd, hdcFrom);
                //Image is created by Image bitmap handle and assigned to Bitmap variable.
                bmp = System.Drawing.Image.FromHbitmap(hBitmap);
                //Delete the compatible bitmap object. 
                DeleteObject(hBitmap);

                bmp.Save("here comes my link where it needs to be saved", ImageFormat.Bmp);

            }

            return bmp;

        }

As stated above, it doesn't work when my window is hidden. Everything works except when my window is hidden. Does anyone have an idea how I can create a bitmap (not a black one) when my window is hidden?

Any help is greatly appreciated.

[kvprajapati]

>when hidden it give me a black bitmap.

Have a look at blog.

[Gaurang Patel]

use PrintWindow API. Its works fine.

public System.Drawing.Bitmap CaptureWindow(IntPtr hWnd)
        {
            System.Drawing.Rectangle rctForm = System.Drawing.Rectangle.Empty;

            using (System.Drawing.Graphics grfx = System.Drawing.Graphics.FromHdc(GetWindowDC(hWnd)))
            {
                rctForm = System.Drawing.Rectangle.Round(grfx.VisibleClipBounds);
            }

            System.Drawing.Bitmap pImage = new System.Drawing.Bitmap(rctForm.Width, rctForm.Height);
            System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(pImage);

            IntPtr hDC = graphics.GetHdc();
            //paint control onto graphics using provided options        
            try
            {
                PrintWindow(hWnd, hDC, (uint)0);
            }
            finally
            {
                graphics.ReleaseHdc(hDC);
            }
            return pImage;


        }

[RicardoCleves]

The code posted by Gaurang Patel did the trick, awesome!.
The only thing that's missing is a couple of DLLIMPORTs:

[DllImport("user32.dll")]
public static extern bool PrintWindow(IntPtr hwnd, IntPtr hdcBlt, uint nFlags);

[DllImport("user32.dll")]
public static extern IntPtr GetWindowDC(IntPtr hWnd);