Convert rtf text in XAML

I am trying to convert rtf text in XAML by following  code

            TextRange textRange = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);
            MemoryStream ms = new MemoryStream();
            textRange.Save(ms, System.Windows.DataFormats.Xaml);
            string str = UTF32Encoding.Default.GetString(ms.ToArray());
            ms.Close();

This code successfully converts rtf to XAML.

But My problem is that XAML text  str  loosing image which is inside richTextBox1.