Capture screen, display it on other window

Question

Dear all,

I would like to do function that user can capture specific screen area, and display them on other window. How can I do it with wpf?

The capture function look like "Rectangular Marquee Tool" of Adobe Photoshop but how can I get data of selected-screen.

I come with idea:
  1.  Make a transparent window
  2.  Capture selected screen behind it
  3.  Force selected-screen into image buffer
  4.  Open new window and display image buffer.

What are wpf controls should I use for this purpose?

Thank for any recommendation.

Best,

Answer 1

U can try with some API functions for capturing screen.

Answer 2

Thank you for you comment.

Could you give me some guide more detail?

Best,

Answer 3

-> What are wpf controls should I use for this purpose?

System.Windows.Controls.Image should be able to do the trick, you could call the GDI GetDesktopDC to do the trick, capture the screen into hBimtap, and bring the hBimtap into WPF world using Imaging.CreateBitmapSourceFromHBitmap() method.

hope this helps

Answer 4

Thank for your guide.

But I can not get data. What is it wrong?

         {
              int screenWidth = (int)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width;
              int screenHeight= (int)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height;
              IntPtr hwnd       = NativeMethods.GetDesktopWindow();
              IntPtr windowDC   = NativeMethods.GetWindowDC(hwnd);
              IntPtr memDC      = NativeMethods.CreateCompatibleDC(windowDC);
              IntPtr hbm        = NativeMethods.CreateCompatibleBitmap(windowDC, screenWidth, screenHeight);
              IntPtr oldbm      = NativeMethods.SelectObject(memDC, hbm);

              bool b = NativeMethods.BitBlt(memDC, 0, 0, screenWidth, screenHeight, windowDC, 0, 0, 0x40CC0020);
              System.Drawing.Bitmap tempBitmap  = System.Drawing.Image.FromHbitmap(hbm);
              IntPtr                tempHBitmap = tempBitmap.GetHbitmap();

              bitmapSrc = Imaging.CreateBitmapSourceFromHBitmap(tempHBitmap, IntPtr.Zero, Int32Rect.Empty,
                                                                             BitmapSizeOptions.FromEmptyOptions());
              NativeMethods.SelectObject(memDC, oldbm);
              NativeMethods.DeleteObject(hbm);
              NativeMethods.DeleteDC(memDC);
              NativeMethods.ReleaseDC(hwnd, windowDC);
              NativeMethods.DeleteObject(tempHBitmap);
              tempBitmap.Dispose();             
          }

 class NativeMethods
    {
        // This is a call to unmanaged code.     
        [DllImport("user32.dll")]
        //Get a pointer to the desktop window
        public extern static IntPtr GetDesktopWindow();

        [DllImport("user32.dll")]
        //Get a device context from the desktop window
        public static extern IntPtr GetWindowDC(IntPtr hwnd);
        //[DllImport("gdi32.dll", EntryPoint = "CreateCompatibleDC")]
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hdc);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hdc, IntPtr bmp);       
        [DllImport("gdi32.dll")]
        public static extern IntPtr DeleteObject(IntPtr hDc);
        [DllImport("gdi32.dll")]
        public static extern IntPtr DeleteDC(IntPtr hDc);
        [DllImport("user32.dll")]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDc);


        [System.Runtime.InteropServices.DllImport("gdi32.dll")]
        public static extern bool BitBlt
             (IntPtr hDestDC,       // handle to destination DC
             int nXDest,            // X-coordinate of destination upper-left corner
             int nYDest,            // Y-coordinate of destination upper-left corner
             int nWidthDest,        // Width of destination rectangle
             int nHeightDest,       // Height of destination rectangle
             IntPtr hSrcDC,         // Handle to source DC
             int nXSrc,             // X-coordinate of source upper-left corner
             int nYSrc,             // Y-coordinate of source upper-left corner
             int rasterOp  // raster operation code
            );
    }

Answer 5

Have you tried directly passing the hBitmap returned from CreateCompatibleBitmap() to the Imaging.CreateBitmapSourceFromHBitmap() method without kicking off the System.Drawing.Bitmap intermediary at all?

I've done that before, and if I remember correctly, it can do the trick, let me know if it works for you.

Thanks

Answer 6

Hi Marco Zhou,

Its not work for me. And I saved as file and load file again to display image in wpf control.

Thanks