Coded Test Step - How do I get the bitmap from ArtOfTest.WebAii.Controls.Xaml.Wpf.Image ?

In a coded test, I’m trying to compare an image displayed in a ArtOfTest.WebAii.Controls.Xaml.Wpf.Image control with an image I have on the file system. This would be quite straightforward in WPF, but how do I get the bitmap (either as a byte[] or System.Drawing.Bitmap) from ArtOfTest.WebAii.Controls.Xaml.Wpf.Image control? 

Thanks