hexcolortoner

#!/usr/bin/env bash

# take a color as hexadecimal input and convert it to a lighter or darker variant

# usage hexcolortoner hexcolor amount
# amount should be -ve to make color darker, +ve for lighter

hex=$1

if test -z "$1"; then
	echo -n "Type a hex color: "
	read -r hex
fi

initpound=$(echo "$hex" | grep -o '^#')
hex=$( echo "$hex" | cut -d'#' -f2)

hextoint() {
	echo "$(( 16#$1 ))"
}

inttohex() {
	printf "%02x\n" "$1"
}

amount=$2

if test -z "$2"; then
	echo -n "Type amount to change: "
	read -r amount
fi

if test "$(echo -n "$hex" | wc -c)" -ne 6; then
	echo "Hex color has to be 6 digits"
	exit 1
fi
red=$(hextoint "$( echo "$hex" | cut -c1-2 )" )
green=$(hextoint "$( echo "$hex" | cut -c3-4 )" )
blue=$(hextoint "$( echo "$hex" | cut -c5-6 )" )
(( red+=amount ))
(( green+=amount ))
(( blue+=amount ))
if test "$red" -gt 255; then red=255; fi
if test "$green" -gt 255; then green=255; fi
if test "$blue" -gt 255; then blue=255; fi
if test "$red" -lt 0; then red=0; fi
if test "$green" -lt 0; then green=0; fi
if test "$blue" -lt 0; then blue=0; fi
rh=$(inttohex $red)
gh=$(inttohex $green)
bh=$(inttohex $blue)
echo "${initpound}${rh}${gh}${bh}"