lightweighter.sh

#!/bin/bash

set -o errexit
set -o pipefail
set -o nounset

trap 'echo "Ctrl-C captured and exit."; exit 1' INT
trap 'echo "some error occured at $(pwd) and exit."; exit 8' SIGHUP

mkdir -p outdir || exit 1

find . -type f \( -iname '*.jpg' -or -iname '*.png' -or -iname '*.jpeg' -or -iname '*.gif' \) -print0 | \
while read -d $'\0' i; do
  echo convert "$i" -geometry 1200x -compress jpeg -quality 85 "outdir/${i%.*}.jpg"
  convert "$i" -geometry 1200x -compress jpeg -quality 85 "outdir/${i%.*}.jpg" || kill -hup $$
done

rm -f *.jpg *.png *.JPG *.PNG *.JPEG && \
 mv outdir/* . && \
 rm -rf outdir