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Tags: ubuntu-gnome   xrandr   redshift   f.lux   gamma   eyesome  
Link: πŸ” See Original Answer on Ask Ubuntu πŸ”—

URL: https://askubuntu.com/q/1061304
Title: How to use "xrandr --gamma" for Gnome "Night Light"-like usage?
ID: /2018/08/01/How-to-use-_xrandr-gamma_-for-Gnome-_Night-Light_-like-usage_
Created: August 1, 2018    Edited:  December 17, 2021
Upload: November 24, 2022    Layout:  post
TOC: false    Navigation:  false    Copy to clipboard:  false


December 9, 2018 Update - sct

I found source code for program sct which allows user to set color temperature. It has β€œcribbed the code” from redshift and provides mapping for red, green and blue values:

/* cribbed from redshift, but truncated with 500K steps */
static const struct { float r; float g; float b; } whitepoints[] = {
    { 1.00000000,  0.18172716,  0.00000000, }, /* 1000K */
    { 1.00000000,  0.42322816,  0.00000000, },
    { 1.00000000,  0.54360078,  0.08679949, },
    { 1.00000000,  0.64373109,  0.28819679, },
    { 1.00000000,  0.71976951,  0.42860152, },
    { 1.00000000,  0.77987699,  0.54642268, },
    { 1.00000000,  0.82854786,  0.64816570, },
    { 1.00000000,  0.86860704,  0.73688797, },
    { 1.00000000,  0.90198230,  0.81465502, },
    { 1.00000000,  0.93853986,  0.88130458, },
    { 1.00000000,  0.97107439,  0.94305985, },
    { 1.00000000,  1.00000000,  1.00000000, }, /* 6500K */
    { 0.95160805,  0.96983355,  1.00000000, },
    { 0.91194747,  0.94470005,  1.00000000, },
    { 0.87906581,  0.92357340,  1.00000000, },
    { 0.85139976,  0.90559011,  1.00000000, },
    { 0.82782969,  0.89011714,  1.00000000, },
    { 0.80753191,  0.87667891,  1.00000000, },
    { 0.78988728,  0.86491137,  1.00000000, }, /* 10000K */
    { 0.77442176,  0.85453121,  1.00000000, },
};

The three columns above are values for Red, Green and Blue.

November 4, 2018 Update - Eyesome

I wrote a collection of bash scripts called Eyesome that adjust brightness and gamma gradually at dawn and dusk over a 90 minute to 120 minute period. Although user can change the settings, a good starting point for full brightness setting is:

xrandr --output DP-1-1 --gamma 1:1:1 --brightness 1.0

The nighttime setting (for one of the three monitors) is:

xrandr --output DP-1-1 --gamma 1.0:0.88:0.76 --brightness 0.55

Note: Up to three monitors can be defined with separate settings.


Original Answer

Finally found one answer: MORE OF XRANDR OR BLUE LIGHT EXPOSURE This script is presented:

#!/bin/sh 

night_mode() { 
  for disp in $(xrandr | sed -n 's/^\([^ ]*\).*\<connected>.*/\1/p'); do 
    xrandr --output $disp --gamma $1 --brightness $2 
  done } 
case $1 in 
  off) night_mode 1:1:1 1.0 ;; 
  *) night_mode 1:1:0.5 0.7 ;;
esac

The script reduces blue light component and brightness of all Xorg displays attached. Simply save it in your bin directory, chmod +x it and, if you want to, add a cron job or keyboard shortcut to call the function.

How it works? Simply type in the script name without any parameters to reduce blue light. To return to normal setting, add off parameter after the command.

⇧ How to change the Ubuntu 18.04 default greeter? How to disable pulseaudio automatic device switch?  β‡©