How could I dim the display brightness of a desktop PC while using Plasma 5 on GNU/Linux?

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I'm using Plasma 5 for GNU/Linux in a desktop PC box. I would need a way to dim display brightness, but I have absolutely no idea where to start looking for it. Whatever you come up with, CLI solutions are welcome, but it's not necessary for me to have a CLI solution.

This is how the Battery and Brightness plasmoid is rendering:

enter image description here

I was expecting the plasmoid to be provisioned with a Display Brightness slider, but it is not there. Is there a way to bring it appearing? Should I open issue at KDE?

174140

Posted 2017-11-29T09:49:09.600

Reputation: 859

could you not DIM the actual monitor itself using its own menu options? – TiO – 2017-11-29T09:59:38.820

1In case you were asking about manipulating hardware controls. – 174140 – 2017-11-29T10:11:48.737

@TiO, there are scenarios where adjusting the monitor isn't the best solution. For example, multi-booting. If each OS is adjusted, you don't need to readjust the monitor when you change OS. – fixer1234 – 2017-11-30T01:46:13.280

@uprego, that picture in your comment is just bragging. :-) – fixer1234 – 2017-11-30T01:47:13.167

@fixer1234 the need is for a PC set with only three displays. The picture for me is just convenience multi media stock extracted from the Internet. – 174140 – 2017-11-30T12:08:21.850

Answers

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You won't be able to modify monitor brightness over HDMI, or any other display connector AFAIK.

The next best thing is to use a color management profile to dim the display using software. This results in worse color accuracy and won't work when not in the Desktop Environment, but when you have 8 monitors it seems like your only choice.

Use lprof to create a color profile with the brightness you want, you should be able to ignore most of the process and just use the defaults.

After creating a color profile, you can use oyranos-monitor to change between it and the normal color profile via the command line.

Doctor Nefario

Posted 2017-11-29T09:49:09.600

Reputation: 46

This answer is poor, it does not provide easy to follow instructions. I cannot add any additional information because I am not using a GNU/Linux distro right now. – Doctor Nefario – 2017-11-29T11:08:23.840

I don't hang around superuser.com so much as previously, enough to know which are the current recommended standards for answers, but still I find that comment over self deprecation. This way to go is indeed some work, specially given I can solve the problem turning on the ambient lights of the room, but there is a lot of value in pointing to the best available resources and ways and even if there was an easier way to go there is a lot of value in pointing any useful resource and high level recipe. To me this is looking a lot worth trying. – 174140 – 2017-11-29T13:23:45.400

OK, I understand you now. I am turning on the lights. – 174140 – 2017-11-29T15:01:21.377

If you knew how to fix this for my PC that would be awesome.

– 174140 – 2017-12-01T08:59:04.963

What step in that solution aren't you able to follow? If you can set the brightness for one of the monitors then you can probably write a simple bash script to change them all at once. What is your output of xrandr -q | grep -w connected? – Doctor Nefario – 2017-12-02T07:58:24.850

Asked: 2017-11-29T09:49:09.600

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Active: 2017-11-29T11:05:18.370