Using RenderTargetBitmap on WindowsFormsHost

Question

I have a set of controls inside a WindowsFormsHost and I would like to capture the current view and just save it as an image, I however only get some Pane

Answer 1

A Windows Forms control also knows how to render itself, you don't have to jump through the screen capture hoop. Make it look like this:

    using (var bmp = new System.Drawing.Bitmap(basePanel.Width, basePanel.Height)) {
        basePanel.DrawToBitmap(bmp, new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height));
        bmp.Save(@"c:\temp\test.png");
    }

Answer 2

The content of the WindowsFormsHost is rendered by GDI+, like in a Windows Forms application, so you can't use RenderTargetBitmap for that since it is not rendered by WPF. Instead, you should use the GDI+ BitBlt function, which allows you to make a capture of an area on the screen.

See this post for an example

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UPDATE: here's another version of the code, updated for use with WPF :

using System.Drawing;
...

public static ImageSource Capture(IWin32Window w)
{
    IntPtr hwnd = new WindowInteropHelper(w).Handle;
    IntPtr hDC = GetDC(hwnd);
    if (hDC != IntPtr.Zero)
    {
        Rectangle rect = GetWindowRectangle(hwnd);
        Bitmap bmp = new Bitmap(rect.Width, rect.Height);
        using (Graphics destGraphics = Graphics.FromImage(bmp))
        {
            BitBlt(
                destGraphics.GetHdc(),
                0,
                0,
                rect.Width,
                rect.Height,
                hDC,
                0,
                0,
                TernaryRasterOperations.SRCCOPY);
        }
        ImageSource img = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
            bmp.GetHBitmap(),
            IntPtr.Zero,
            Int32Rect.Empty,
            BitmapSizeOptions.FromEmptyOptions());
        return img;
    }
    return null;
}

Just call pass your WindowsFormsHost control as a parameter to the Capture method, and do whatever you like with the resulting ImageSource. For the definitions of BitBlt and GetDC, have a look at this website (I wrote that on my home computer, which I can't access from where I am now)