jpgcompress

#!/bin/sh
#
# NAME
#
#   jpgcompress - compress JPG files using ImageMagick
#
# SYNOPSIS
#
#   jpgcompress [<file>...]
#
# DEPENDENCIES
#
#   mogrify(1) and stat(1)
#

for img
do
    [ "${img##*.}" = "jpg" ] || [ "${img##*.}" = "jpeg" ] || continue
    a=$(stat -c%s "$img")
    mogrify -auto-orient -strip -interlace JPEG -gaussian-blur 0.05 -quality 85% "$img"
    b=$(stat -c%s "$img")
    printf >&2 "$img %s%%\n" $(echo "scale=2; ($a - $b)*100/$a" | bc)
done