After testing on 2 PCs, I found the following:
On some integrated cards like Intel you can use
xrandr in console. For example:
Go to console (Ctrl+Alt+T)
xrandr -x will flip de video horizontally like a mirror.
xrandr -y will flip de video vertically.
xrandr -y -x will flip both.
xrandr -o normal will return to normal the video.
xrandr -o inverted will...invert O.o
But if you have an Nvidia this may not work. For an Nvidia to work you need to:
Edit you xorg.conf:
sudo nano /etc/X11/xorg.conf
Find the section that has Driver "nvidia" in it
Copy and paste the following at the end of that section: Option "RandRRotation" "on"
This will activate the rotation for Nvidia which comes off by default. Why off by default i do not know.
After that reboot and you can change the orientation BUT NOT the reflection. What i mean with this is that Nvidia does not yet support reflection options like
-y options in
xrandr. I will keep searching for some more since the question is interesting.