batch-scale

#!/usr/bin/env bash

usage () {
    echo "batch-scale [OPTION...] INPUTFILE OUTPUTFILE"
    echo "Read the INPUTFILE image, scale it to fit in a square,"
    echo "and write the result into OUTPUTFILE."
    echo " Options:"
    echo "   -s PIXELS  Size of the square's side, in pixels."
    echo "              e.g. 640, 800, 1024 (default: 800)"
    echo "   -h         Show this help."
}

scale () {
    gimp -ib '(batch-scale '"$1"' "'"$2"'" "'"$3"'") (gimp-quit 0)'
}

pixels=800

while getopts hs: opt
do
    case "$opt" in
	s)
	    pixels="$OPTARG"
	    ;;
	h)
	    usage
	    exit 0
	    ;;
	'?')
	    exit 1
	    ;;
	*)
	    echo "unhandled option {$opt}" 1>&2
	    exit 1
	    ;;
    esac
done
shift "`expr $OPTIND - 1`"

# There should be two arguments left: INPUTFILE OUTPUTFILE.
if [ "$#" -lt 2 ]
then
    echo "missing argument" 1>&2
    exit 1
elif [ "$#" -gt 2 ]
then
    echo "too many arguments" 1>&2
    exit 1
fi

input="$1"
output="$2"

scale "$pixels" "$input" "$output"