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SL5net
Asked: 2020-11-06 22:41:15 +0800 CST

Permanently set monitor brightness

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I increase and reduce the LCD brightness on the command line as described here1:
xrandr --output HDMI-0 --brightness 0.2

My problem is that my brightness setting is automatically reset after a few seconds.

My workaround is a small Autokey (Python) script (gist) that permanently sets my setting.
How can it be done better without this little unnecessary extra CPU load?

Operating System: Kubuntu 20.04

KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.4.0-52-generic
OS Type: 64-bit

1: By the way: There is a question with the same name, but it describes a slightly different problem. Is there a way to permanently set the brightness level

kde kubuntu brightness

2 Answers

  1. Best Answer

    That must be due to Redshift/Night Color. Use the command sudo apt remove redshift to uninstall redshift. In case Night Color is enabled, disable it in system settings.

    If you are using a laptop, you can control brightness with the function keys, there's no need to use xrandr.

    If you are using a desktop, you can use Brightness Controller, which is a GUI tool to control brightness, and it can also change the color temperature (it uses xrandr in the backend)

    sudo add-apt-repository ppa:apandada1/brightness-controller
sudo apt update
sudo apt install brightness-controller

    image

    (disclaimer - I am one of the developers of this software)

    You will have to disable Night Color to use Brightness Controller (note that it does not work with Wayland).

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  2. This is a long-known open (Nov2020) bug with redshift (bug open since 2015). Described here githubredshift issues 175 and something similar here how-to-use-xrandr-gamma-for-gnome-night-light-like-usage.

    Some Workarounds (not yet completely substitute solutions):

    most of they does not change automatically depending on day time and recommends detestation of redshift

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