Bash script for recursive compress of jpg files

compress-jpg.sh

#!/bin/bash
if [ -z "$1" ] || [ -z "$2" ]
    then echo "
Usage: script [directory] [quality] [change files]

Requirements: ImageMagic (convert, identify), jpegoptim

Arguments:
directory - script take all jpg files from directory
quality - jpg quality value (0-100); if file has higher quality will be processed lossy, otherwise lossless
additional options (optional)
change files - if true files will be changed, otherwise (default) then will not change any files (test run)

Script flow:
- find all jpg|jpeg|JPG|JPEG files in \"directory\"
- if file has quality higher than argument \"quality\" convert it to target quality
- if file has size lower than 10KB use non progressive option (better result for final file size)
- if file has size bigger than 10KB use progressive option
- optimize image

Default options for jpegoptim are: p,s
p - preserve file timestamp
s - strip all markers (xmp, iptc etc.)

Example:
./compress-jpg.sh img-test/ 93 -n
"
else
    # Progressive option is inefficient for small images; that is "normal" will make smaller files
    PROGRESSIVE_THRESHOLD=10240
    dirName=$1
    qualityThreshold=$2
    # changeFiles=$3
    changeFiles=$3

    startDirSize=$(du -s $dirName | cut -f 1)

    # Removing possible error.log without errors
    touch error.log && rm error.log

    find $dirName -type f \( -iname \*.jpg -o -iname \*.jpeg \) | while read file; do
        echo "----------"
        fileQuality=$(($(identify -verbose "$file" | grep 'Quality:' | sed 's/[^0-9]//g')))
        fileSize=$(stat --printf="%s" "$file")

        # File conversion should be before checking progressive option, because conversion changes file size.
        optionQuality=" "
        if (($fileQuality > $qualityThreshold)) && [[ $changeFiles == true ]]; then
            # Convert (imageMagic) use much better quality in lossy compression, so we don't using jpegoptim to this, although
            # it can do it.
            convert -quality $qualityThreshold "$file" "$file"
        fi

        optionProgressive=" "
        if (($fileSize > $PROGRESSIVE_THRESHOLD)); then
            optionProgressive="--all-progressive"
        else
            optionProgressive="--all-normal"
        fi

        if [[ $changeFiles == true ]]; then
            jpegoptimNoAction=""
        else
            jpegoptimNoAction="-n "
        fi

        command="jpegoptim -p -s $optionQuality $optionProgressive $jpegoptimNoAction \"$file\""
        echo $command
        eval $command 2>> error.log
    done;
    echo "=========="
    endSize=$(du -s $dirName | cut -f 1)
    diffSize=$(($startDirSize - $endSize))
    diffPercent=$(($(($diffSize*100))/$startDirSize));
    echo "Saved $diffSize KB ($diffPercent%)"
    if [ -s error.log ]; then
        printf "Errors:\n" && cat error.log
    else
        rm error.log 2> /dev/null
    fi
fi