go to file -> print setup
enter settings of your printer
select Landscape Format and click ok, close print-setup
select an image and go to file -> print
select Portait or Landscape under Orientation
-> The print preview looks very very bad!
Take a look at this screenshot. In background, there's the real picture.
In preview there are some strange red dots....
It also doesn't recognize the aspect-ratio.

But: In general, the print preview looks always a little bit strange...there are colors which aren't in the pictures...
This preview was much better in older xnview versions.
At the moment, I can't use print-function in cause of these strange bugs...