Small helper script to resize and guetzlify jpgs via command line

convert_images.sh

#!/bin/bash
PROGNAME=$0

usage() {
  cat << EOF >&2
Usage: $PROGNAME [-q <quality>] [-s <scale_shortest_side>] [-s <scale_largest_side>]

-q <quality>: quality of guetzli process | default [85]
-l <scale>: the scale of the largest side of the image
-s <scale>: the scale of the shortest side of the image
EOF
  exit 1
}

#
# Minify images using the guetzli algorithm
# https://github.com/google/guetzli
# It can be very slow.
# Dont use it in a CI process.
#
guetzlify(){
  echo "guetzlying $1"
  guetzli --quality $2 "$1" "$1"
}

prepare_guetzlify(){
  if [ -d "$1" ]; then
    # is directory
    find "$1" -type f -name "*.jpg" -print0 | while IFS= read -r -d '' file;
    do
      guetzlify "$file" "$2"
    done
  elif [[ -f "$1" ]] && [[ $1 == *.jpg || $1 == *.jpeg ]]; then
    guetzlify "$1" "$2"
  else
    echo "$1 not found"
  fi
}

#
# Resize images using imagemagick
#
resize() {
  echo "resizing $1"
  cmd="x$2>"
  # check the aspect ratio
  [ $(identify -format $check "$1") -eq 1 ] && cmd="$2x>"
  convert "$1" -resize $cmd "$1"
}

prepare_resize(){
  if [ ! -z $2 ]; then
    check="%[fx:w<h?0:1]"
    scale=$2
  elif [ ! -z $3 ]; then
    check="%[fx:w>h?0:1]"
    scale=$3
  else
    return
  fi
  if [ -d "$1" ]; then
    # is directory
    find "$1" -type f -name "*.jpg" -print0 | while IFS= read -r -d '' file;
    do
      resize "$file" "$scale"
    done
  elif [[ -f "$1" ]] && [[ $1 == *.jpg || $1 == *.jpeg ]]; then
    resize "$1" "$scale"
  else
    echo "$1 not found"
  fi
}

quality=85
while getopts q:s:l: o; do
  case $o in
    (q) quality=$OPTARG;;
    (l) scaleLargest=$OPTARG;;
    (s) scaleShortest=$OPTARG;;
    (*) usage
  esac
done
shift "$((OPTIND - 1))"

path=$1

if which guetzli >/dev/null && which convert >/dev/null; then
  for arg in "$@" ; do
    prepare_resize "$arg" "$scaleLargest" "$scaleShortest"
    prepare_guetzlify "$arg" $quality
  done
else
  brew update
  brew install guetzli imagemagick
  for arg in "$@" ; do
    prepare_resize "$arg" "$scaleLargest" "$scaleShortest"
    prepare_guetzlify "$arg" $quality
  done
fi