Sepia mode in Ubuntu

sepia_screen.sh

#!/bin/bash

# Inspired by:
# https://opensource.com/article/20/4/linux-astronomy
# https://askubuntu.com/a/207435
# Prerequirements: You must install `xcalib` command by typing: sudo apt install xcalib

case $1 in
    on)
        # adjust color, gamma, brightness, contrast
        xcalib -red 1.7 1 64 -green 1.7 1 57 -blue 1.7 1 28 -alter
        exit 1
    ;;
    off)
        xcalib -clear
        exit 1
    ;;
    inv)
        # Invert screen
        xcalib -i -a
        exit 1
    ;;
    dim)
        # Make the screen darker
        xcalib -clear
        xcalib -co 30 -alter
        exit 1
    ;;
    *)
        echo "$0 [on | dim | inv | off]"
        exit 1
    ;;
esac