how to display a full WUXGA "test pattern" on the laptop?

[stan]

Robert P. J. Day wrote:
>   almost certainly a dumb question, but i've never tried this before
> -- if i have a 1920x1200, say, png file, how can i display it *fully*
> on a laptop display, temporarily overriding the menu bars and so on?
> thanks.
> 
> rday
> 
> p.s.  ideally, i guess i'd want to need to press ESC to get back to a
> normal desktop.
> 
Install qiv

Then   qiv -m filename   will make it fit the screen.
f will go to full screen.
Finally q will get you out.
b and Shift-b alter brightness.
- and +/= alter size.