This script re-sizes and optionally renames files in the current folder using the Imagemagick convert program.

batch_resize

#!/usr/bin/env bash
# 
# By Drew Hornbein @ http://dhornbein.com
# 
# Description: The following script will take image files from 
# the current folder and run the Imagemagick convert function.
# A log.txt file will be created in the new folder
#
# Dependencies:
# imagemagick - we use the convert program
# 
# Options:
# 
# -n file_name
# new name: If you wish to rename all files add this flag.
# The new name will be numerated like so: new_name_001.jpg
# 
# -s 1200x
# size: pass a argument to convert's resize flag.
# More info here: http://www.imagemagick.org/script/command-line-options.php#resize
# default: 1200x
# 
# -q 90
# quality: pass a number to convert's quality flag
# 0-100 higher number is higher quality
# default: 90
# 
# -o 'string'
# add option: add additional attributes to the convert function
# 
# -O 'string'
# replace options: completely replace all attributes passed to the convert function
# with the attributes you input.
# 
# -d ./processed/
# destination: where to send the converted files
# default ./processed/
# 
# -v
# verbose: outputs information

set -e

# check for convert
convert -v foo >/dev/null 2>&1 || { echo "imagemagick 'convert' is required to run this script. try: sudo apt-get install imagemagick" >&2; exit 1; }

# set help and useage
HELPTEXT="help: `basename $0` (-n new file name) (-s resize ex: 1200x, 400x500^) (-q quality 0-100) (-o additional convert/mogrify options ex: \"-o '-extent 400x400'\") (-O capital o, replace parameters of convert/mogrify with input) (-d destination /path/name/) (-v verbose output)"
USETEXT="Usage: `basename $0` options (-n new file name) (-s resize) (-q quality) (-o additional convert/mogrify options) (-O replace convert/mogrify options) (-d destination) (-v verbose) -h for help"

# set default values
NEWNAME=false
NEWSIZE="1200x"
IMGQUALITY="90"
NEWOPTIONS=false
DEST=./processed/

if ( ! getopts "n:s:q:o:O:d:vh" opt); then
    echo $USETEXT
fi

while getopts ":n:s:q:o:O:d:vh" opt; do
  case $opt in
    n)NEWNAME="$OPTARG";;
    s)NEWSIZE="$OPTARG";;
    q)IMGQUALITY="$OPTARG";;
    d)DEST=${OPTARG%/}/;;
    o)ADDOPTIONS="$OPTARG";;
    O)NEWOPTIONS="$OPTARG";;
    v)VERBOSE=true;;
    h)
        echo $HELPTEXT
        exit 0
    ;;
    \?)
        echo "Invalid option: -$OPTARG" >&2
        exit 1
    ;;
    :)
        echo "Option -$OPTARG requires an argument." >&2
        exit 1
    ;;
  esac
done

if [[ $NEWOPTIONS == false ]]
then
    echo "(n)ew name: $NEWNAME"
    echo "(s)ize: $NEWSIZE"
    echo "(q)uality: $IMGQUALITY"
    echo "(d)estination: $DEST"
fi

# prevents a null glob to be read
shopt -s nullglob

IMGGLOB=(*.{jpg,jpeg,JPG,JPEG,png,PNG,gif,GIF})
FILESLEN=${#IMGGLOB[@]}

i=1 #count

for INFILE in "${IMGGLOB[@]}"
do
    NUM=$(printf "%0${#FILESLEN}d" $i);
    EXT=${INFILE##*\.}

    if [[ $NEWNAME != false ]];
    then
        FILENAME="${NEWNAME}_${NUM}.${EXT,,}"
    else
        FILENAME="${INFILE}"
    fi

    OUTFILE="$DEST${FILENAME}"

    # check with the user to make sure everything is okay
    if [[ -z $OKAY ]]; then
        
        # build convert command
        if [[ $NEWOPTIONS == false ]]
        then
            convert="convert '$INFILE' -resize '$NEWSIZE' -gravity center -density 72 -quality '$IMGQUALITY' $ADDOPTIONS $OUTFILE"
        else
            convert="convert '$INFILE' $NEWOPTIONS $OUTFILE"
        fi

        echo "This command will be run on each file:"
        echo '$' $convert
        echo -ne "Process these $FILESLEN file(s)? [Y/n]: "
        read process
        if [[ $process == "N" || $process == "n" ]]; then
            echo "aborting..."
            exit 42
        else
            OKAY=true
            mkdir -p "$DEST"
            echo -e "`date` ----------\n$convert" > "${DEST}log.txt"
        fi
    fi

    if [[ $NEWOPTIONS == false ]]
    then
        convert "$INFILE" \
            -resize "$NEWSIZE" \
            -gravity center \
            -density 72 \
            -quality "$IMGQUALITY" \
            $ADDOPTIONS \
            "$OUTFILE"
    else
        convert "$INFILE" \
            $NEWOPTIONS \
            "$OUTFILE"
    fi

    IN="$INFILE ($(du -h "$INFILE" | cut -f1))"
    if [ -f "$OUTFILE" ]; then
        OUT="$OUTFILE ($(du -h "$OUTFILE" | cut -f1))"
    fi

    # build log file
    echo "$IN ---> ${OUT-FAILED!}" >> "${DEST}log.txt"
    
    if [[ $VERBOSE ]]; then
        echo "$NUM $IN --> ${OUT-FAILED!}"
    fi

    (( i += 1 ))
done

notify-send "Conversion Finished of $i files"