Manual screen dimmer for xrandr with color temperature setting

gamma

#!/bin/bash

r=255
g=255
b=255

function apply () {
    echo -n "Enter brightness [0, 1]: "
    read brightness
    while read display; do
        r=$(printf %.6f "$((10**6 * $1/255))e-6")
        g=$(printf %.6f "$((10**6 * $2/255))e-6")
        b=$(printf %.6f "$((10**6 * $3/255))e-6")
        xrandr --output $display --brightness $brightness --gamma $r:$g:$b
    done <<< $(xrandr -q | grep " connected" | grep ^DP | awk '{print $1}')
}
select option in Default "1900K Candle" "2600K 40W Tungsten" "2850K 100W Tungsten" "3200K Halogen" "5200K Carbon Arc" "5400K High Noon" "6000K Direct Sun" "7000K Overcast Sky" "20000K Clear Blue Sky";
do
    case "$option" in
        Default)
            apply 255 255 255
            break
        ;;
        1900K*)
            apply 255 147 41
            break
        ;;
        2600K*)
            apply 255 197 143
            break
        ;;
        2850K*)
            apply 255 214 170
            break
        ;;
        3200K*)
            apply 255 241 224
            break
        ;;
        5200K*)
            apply 255 250 244
            break
        ;;
        5400K*)
            apply 255 255 251
            break
        ;;
        6000K*)
            apply 255 255 255
            break
        ;;
        7000K*)
            apply 201 226 255
            break
        ;;
        20000K*)
            apply 64 156 255
            break
        ;;
    esac
done