I installed xcalib to adjust my screen contrast, and I executed this :
xcalib -co 0 -a
Which set my screen contrast to 0 , and now my screen turned dark, and I don't have any clue as to how can I reset this setting ?
Thank you
As first enter a TTY, this you achieve by pressing ctrl+alt+f1. There you can login whit providing your username and password. Then set the contrast back with the same command you have used to set it to zero.
xcalib -co 50 -a
Now you can logout of your TTY session by entering exit. Afterwards you can come back to your GUI by pressing ctrl+alt+f7.
-c(you'll note that the question also used-c, however; so, I don't think that's enough to say this answer is building off of the accepted answer). It's much simpler than the accepted answer, and it still seems to work. No need to press Ctrl+Alt+F7 or anything like that. Granted, I'm only using this answer for my own purposes (not for what the questioner wanted, exactly). – Brōtsyorfuzthrāx Feb 05 '19 at 20:30