#!/bin/sh
rate=5
scale="scale=-1:-1:flags=lanczos"

usage() {
	echo "Usage: $0 [-i <string>] [-s <integer>] [-r <integer>]"
	echo "Options:"
	echo " i input file"
	echo " s width of the resulting gif"
	echo " r frame rate of the resulting gif"
}

while getopts "s: r: i: h" args; do
	case "$args" in
	i)
		file_name=${OPTARG}
		;;
	s)
		echo $OPTARG
		if [[ $OPTARG =~ ^[0-9]+$ ]]; then
			scale="scale=${OPTARG}:-1:flags=lanczos"
		else
			echo "Error: -s expects an integer." >&2
			exit 1
		fi
		;;
	r)
		if [[ $OPTARG =~ ^[0-9]+$ ]]; then
			rate=${OPTARG}
		else
			echo "Error: -r expects an integer." >&2
			exit 1
		fi
		;;
	h | * | \?)
		usage
		exit
		;;
	esac
done

if [ $OPTIND -eq 1 ]; then 
	usage
	exit
fi

ffmpeg -r ${rate} -i ${file_name}-%d.jpg -vf "${scale}" ${file_name}.gif