Create one or many new resized image files

resize_img.sh

#!/bin/bash


function usage() {
    cat<<EOF
$(basename $0) - Create one or many new resized image files

Usage:
    $(basename $0) <size> <imgfile1> [imgfile2 imgfile3 ...]

EOF
}

function get_filename() {
    filename=$(basename "$1")
    echo "${filename%.*}"
}

function get_extension() {
    filename=$(basename "$1")
    echo "${filename##*.}"
}

function resize_image() {
    local size=$1
    local imgfile=$2
    filename=$(get_filename $imgfile)
    extension=$(get_extension $imgfile)
    imgfile_resized=$(dirname $imgfile)/${filename}"_${size}."${extension}

    convert ${imgfile} -resize ${size} ${imgfile_resized} &&\
        echo "$imgfile -> $imgfile_resized"
}


[ $# -lt 2 ] && usage && exit 1

[ -e $1 ] && echo "$1 must be a valid size. Example (1280, 1280x720 or x720)" && exit 1
size=$1

shift

for arg in "$@"
do
    ! [ -e $arg ] && echo "$arg must be an existing image file" && exit 1
    resize_image ${size} $arg
done

Requires ImageMagick.