Xrandr Scaling script, with auto panning when scaling down

xrandr-scale.sh

#!/bin/bash

export LANG=C

output=$1;
scale=$2;

if [ -n "$output" ] && ! (xrandr --listmonitors | grep -qw "$output"); then
  echo "Invalid output: '$output'";
  exit 1;
fi

modes=$(xrandr | sed -n "/$output/,//{/$output/{p;n};/^[^ ]\+/{q};p}");
selected_mode=$(echo "$modes" | grep '[0-9].\*'| cut -f4 -d' ');
x=$(echo "$selected_mode" | cut -f1 -dx);
y=$(echo "$selected_mode" | cut -f2 -dx);

if [ -z "$scale" ] || ( [ -n "${scale//[0-9]/}" ] && [ "${scale//[0-9]/}" != '.' ] ); then
  echo "Invalid scale input: '$scale'";
  exit 1;
fi

scale=$(echo "scale=4; 1.0 / $scale" | bc);
scaled_x=$(printf "%0.0f" $(echo "scale=4; $x * $scale" | bc));
scaled_y=$(printf "%0.0f" $(echo "scale=4; $y * $scale" | bc));

if [ $(printf "%0.0f" $scale) == "1" ]; then
  panning=0x0;
else
  panning=${scaled_x}x${scaled_y}
fi

echo "Current res is ${x}x${y}, scaling at ${scaled_x}x${scaled_y}";
xrandr --output $output --scale ${scale}x${scale} --panning $panning