[Inkscape-user] Inverting Parts of a black and white graphic

Hello, is there a good way to invert a black and white graphic in inkscape. As an example, take https://github.com/Bouni/MDT-Glas-Push-Button-Template/blob/master/MDT-Gl... and invert the upper or the lower graphic. I tried to add a layer and use exclusive-or with a black box overlay, but I it did not do at all what I was hoping for (xor between black and white). Is there a good way to do that without changing the color of every item? I am an inkscape beginner, so every advice is welcome :-) Many thanks Rainer -- Rainer Dorsch http://bokomoko.de/