Ubuntu – How to get the Redshift functionality of smart adjustment of the color temperature throughout the day in a Wayland session of Ubuntu 17.10

17.10colorsgnomeredshiftwayland

Redshift is a neat little program allowing you to adjust color temperature of the screen during the day and separately during the night. Is it possible to achieve this with GNOME 3 on Ubuntu 17.10?

Under Setting → Devices → Displays GNOME allows to enable Night Light which makes the screen somewhat warmer at night. However, it does not allow to adjust the color temperature, and it doesn't work during the day.

How to replicate the Redshift functionality in Gnome 3 on Wayland?

Best Answer

Not really a good one but kinda half-baked solution is using a GNOME shell extension called "Night Light Slider". It adds a slider to control the colour temperature manually:

(screenshot source: extension's homepage at extensions.gnome.org)

Also you may change Night Light's colour temperature using dconf Editor/gsettings as suggested here: How to adjust the hue (intencity) of gnome night light?

December 9, 2018 Update

I found source code for program sct which allows user to set color temperature. It has "cribbed 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

I wrote a collection of bash scripts to adjust brightness and gamma gradually at dawn and dusk over a 90 minute to 120 minute period. The full brightness setting is:

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

The nighttime setting is:

xrandr --output DP-1-1 --gamma 1.1:0.8:0.7 --brightness 0.55

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.

Ubuntu – How to make the display grayscale

Install the following extension: https://github.com/laerne/desaturate_all

To do this copy the files into a folder called .local/share/gnome-shell/extensions/desaturate_all@nicolas.brack.mail.be

Logout and log back in, then you should be able to enable the extension through gnome-tweak-tool or by browsing to https://extensions.gnome.org/local

Once enabled, grayscale can be quickly turned on and off with the art pallet in the top right coner.

I think you will agree that a grayscale screen with Night Light works better than better Night Light by itself (if you use a color tempeture that is super low). Some things to look for: the scroll bar, the picture of colored penciles, Firefox logo, and the plant in the bottom left.

Here are some comparison screenshots:

Full Color