portrait resize to 4:5 add bars

batch_add_bars_resize.sh

#!/bin/bash
for image_file in *.jpg; do
  width=$(identify -format '%w' "$image_file")
  height=$(identify -format '%h' "$image_file")
  width_difference=$((height * 4/5 - width))
  bar_size=$((width_difference/2))
  echo "adding bar of size" $bar_size
  convert $image_file -bordercolor black -border $((bar_size))x0 -quality 100 $image_file
  echo "resizing from" $width "x" $height "to 1080x1350"
  convert $image_file -resize 1080x1350 -quality 95 $image_file
done