In CEF/Webkit there is a function defined:
  ///
  // Get the raw image data contained in the specified element without
  // performing validation. The specified |width| and |height| dimensions must
  // match the current element size. On Windows |buffer| must be width*height*4
  // bytes in size and represents a BGRA image with an upper-left origin. This
  // method should only be called on the UI thread.
  ///
  /*--cef()--*/
  virtual bool GetImage(PaintElementType type, int width, int height, void* buffer) =0;

I have a middleware c++ project that needs to wrap that function, before I can call it in my main application.  I've attempted to do so with the following code:

WebView.h
virtual bool GetImage(void* buffer);

WebView.cpp
bool WebView::GetImage(void* buffer)
{
    CefRefPtr<CefBrowser> browser;
    if (TryGetCefBrowser(browser))
    {
	return browser->GetImage((cef_paint_element_type_t)0, 0, 0, buffer);
    }
    return false;
}

Application Layer
-----------------
 byte[] buffer = new byte[web_view.Width * web_view.Height * 4];

 unsafe
 {
 	fixed (void* ptr = buffer)
        {
        	web_view.GetImage(ptr);
        }
 }