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For strange reasons best not asked, I have a projector plugged into my computer that is pointed at a mirror. So the computer image is displayed on a wall, but it is mirrored.

In Linux(ubuntu) I can go to display preferences and set the external monitor to have a rotated image. Is there a clever way I could have it set to rotate/flip the image?

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    I like it when questions get funky. Let me see what i can come up with. So let me understand the image comes out of the projector, bounces on the mirror and lands on a wall?
    – Luis Alvarado
    Jan 4, 2011 at 0:01
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    It might depend on the graphics driver you're using. Also, the projector itself might have such an option.
    – Daniel
    Jan 4, 2011 at 2:26
  • Yes the image bounces on the mirror and lands on a wall (if I'm honest on a table, hence the wish for a mirror). I first tried finding an option on the monitor.
    – Gregory
    Jan 4, 2011 at 12:39
  • It's an option on my projector. I didn't know why anyone would ever use such a setting. Now I know, thanks!
    – Marc
    Jun 9, 2013 at 15:26

1 Answer 1

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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:

  1. Edit you xorg.conf: sudo nano /etc/X11/xorg.conf

  2. Find the section that has Driver "nvidia" in it

  3. 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 -x or -y options in xrandr. I will keep searching for some more since the question is interesting.

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    If you are testing this sort of thing without the mirror set up, then I suggest first entering xrandr -o normal so you can press up,up,enter without twisting your head. :)
    – Gregory
    Jan 4, 2011 at 12:47
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    I like your attitude to funky questions. Using xrandr -x worked, but it would turn off the primary monitor (which I wanted to use unflipped). Anyway you led me to xrandr --help and after some thinking came to the following command which does what I want. xrandr --output VGA1 --reflect x
    – Gregory
    Jan 4, 2011 at 12:48
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    I just spent entirely way too much time playing with this and laughing manaically. I think I have spent too much time in front of my screen today.
    – Wayne Werner
    Jan 21, 2016 at 19:35
  • It's 2021 now and it works with NVIDIA as well.
    – Tiana
    Sep 5, 2021 at 23:48

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