Optimize image files for web site.

Dockerfile

# Docker image with ImageMagick installed
#
# To build a docker image, execute:
#   docker build -t imagick .
#
# To create a docker container, execute:
#   docker run -it --rm --name imagick -v ${PWD}:/mydata -w /mydata imagick

FROM ubuntu:19.04
RUN apt-get update \
    && apt-get -y install imagemagick

optimize-images.sh

#! /bin/bash

# Optimize image files:
#    - Source is specified in ARG[1], default "upload"
#    - Target is specified in ARG[2], default "output"
#    - Process recursively
#    - Preserve (mirror) directory structure and file names
#    - Process JPG files (METHOD_JPG=<optimize-method>)
#    - Process PNG files (METHOD_PNG=<optimize-method>)
#    - Process OTHER files (METHOD_OTHER=<optimize-method>)
#    - Optimize method "copy"
#    - Optimize method "jpg"
#    - Optimize method "skip"
#    - Copy (preserve) files with optimization error
#    - (jpg) For files not exceeding JPG_SMALL_LIMIT bytes apply "copy" optimization
#    - (jpg) apply quality JPG_QUALITY
#    - (jpg) resize to MAX_WIDTH and/or MAX_HEIGHT
#
#
# Usage: optimize-images.sh [<input-directory> [<output-directory>]]
#
# GitHub: https://gist.github.com/ivangeorgiev/5f9a4e5d0ec8fea71105fc5f9e8963c2
#

################################################################
#                BEGIN CONFIGURATION                           #
################################################################
# Directories
IN_DIR=${1:-upload}
OUT_DIR=${2:-output}
# Optimization methods per file type
METHOD_PNG=jpg
METHOD_JPG=jpg
METHOD_OTHER=copy
# Optimization settings
MAX_WIDTH=800
MAX_HEIGHT=600
JPG_QUALITY=82
JPG_SMALL_LIMIT=30000
################################################################
#                  END CONFIGURATION                           #
################################################################


################################################################
#                BEGIN OPTIMIZATION METHODS                    #
################################################################


function optimize_copy() {
   local message=${1:-(copy) $f}
   echo $message
   cp $f $OUT_DIR/$f
}

function optimize_skip() {
   local message=${1:-(skip) $f} 
   echo $message
}

function optimize_jpg() {
   echo -n "(jpg)"
   if (( $fsize > $JPG_SMALL_LIMIT )); then
       echo " $f"
       if ! convert $f -quality ${JPG_QUALITY} -resize "${MAX_WIDTH}>" -resize "x${MAX_HEIGHT}>" jpeg:$OUT_DIR/$f; then
           echo -n " --- JPEG Error: "
           optimize_copy
       fi
   else
       echo -n "[small: $fsize B]"
       optimize_copy
   fi
}

################################################################
#                  END OPTIMIZATION METHODS                    #
################################################################


################################################################
#                   BEGIN FILE TYPE HANDLERS                   #
################################################################

function handle_other() {
   echo -n "OTHER: "
   optimize_$METHOD_OTHER
}

function handle_jpg() {
   echo -n "JPG: "
   optimize_$METHOD_JPG
}

function handle_png() {
   echo -n "PNG: "
   optimize_$METHOD_PNG
}

################################################################
#                     END FILE TYPE HANDLERS                   #
################################################################



################################################################
#                        BEGIN MAIN                            #
################################################################


echo Processing $IN_DIR

for f in $(find $IN_DIR -type f | sort); do
   fname=$(basename $f)
   dname=$(dirname $f)
   fext=${fname##*.}
   fsize=$(stat -c%s "$f")
   mkdir -p ${OUT_DIR}/$dname
   
   case $fext in
      jpg | jpeg | JPG | JPEG)
        handle_jpg
      ;;
      
      png|PNG)
        handle_jpg
      ;;
      
      *)
        handle_other
      ;;
   esac
done