Optimizing JPEG graphics files with ImageMagick

A script for optimizing JPGs with ImageMagick below.

The script

#!/usr/bin/env bash

# script : optimize_jpegs.sh
# description : optimize JPEG images in place
# prerequisites : ImageMagick program suite installed on the system 
# Author : Sylwester Wojnowski
# WWW : wojnowski.net.pl
# Usage : optimize_jpegs.sh directory [quality]
#   directory - path to an existing directory on the system where images in JPEG format are kept
#   quality - percentage in range of 1 - 99, 70% by default
# Example : optimize_jpegs.sh /tmp/my/jpegs 65% 

optimize_jpegs(){
  printf "Beginning JPEG files optimization ...\n"  
  local source_dir=${1%/}
  local quality=${2:-"70%"}
  
  local count=0  
  
  local space_total_raw_before=$(du -hs "$source_dir")
  local space_total_before="${space_total_raw_before/%[[:blank:]]${source_dir}}"

  local space_total_raw_after=
  local space_total_after=

  [[ -z $( which mogrify ) ]] && {
    printf "ImageMagick not installed on the system. Exiting ...\n";
    exit 1;
  }

  [[ ! -d "$source_dir" ]] && {
    printf "$source_dir is not a directory on the system. Exiting ...\n";
    exit 1;
  }

  local p_reg='^([1-9]|[1-9][0-9])%$';
  [[ ! $quality =~ $p_reg ]] && {
    printf "Quality parameter not in range. The correct range is 1 - 99 %. Exiting ...\n"
    exit 1;
  }
  
  shopt -s extglob;
  
  while read -r -d ''; do
    mogrify -strip -interlace Plane -quality "$quality" -define jpeg:dct-method=float -sampling-factor 4:2:0 "$REPLY"
    (( count++ ))
    printf '.'
  done < <( find "$source_dir"/*\.jp?(e)g -print0 )
  printf '\n';

  shopt -u extglob  

  space_total_raw_after=$(du -hs "$source_dir")
  space_total_after="${space_total_raw_after/%[[:blank:]]${source_dir}}";
  
  printf "Optimization complete!\n"
  printf "  $count JPEG files optimized and saved to: $source_dir.\n" 
  printf "  Total space taken before optimization: %s, Space taken after: %s\n" "${space_total_before}" "${space_total_after}"
}

optimize_jpegs "$1" "$2"

Run it

Optimizing JPEG files in /tmp/my/jpegs to 70% quality ( default ).

optimize_jpegs.sh /tmp/my/jpegs

Optimizing JPEG files in /tmp/my/jpegs to 60% quality.

optimize_jpegs.sh /tmp/my/jpegs 60%