#!/bin/bash -eu

usage() {
	echo >&2 "usage: $0 <input> <output>"
	exit 1
}

[[ $# == 2 ]] || usage
FW_INFILE="$1"
FW_OUTFILE="$2"

MIME=`file -b --mime-type "$FW_INFILE"`

case $MIME in
	image/gif)
	giftopnm "$FW_INFILE" > "$FW_OUTFILE" 2>/dev/null
	;;
	image/jpeg |\
	image/jpg)
	jpegtopnm "$FW_INFILE" > "$FW_OUTFILE" 2>/dev/null
	;;
	image/png)
	pngtopnm "$FW_INFILE" > "$FW_OUTFILE" 2>/dev/null
	;;
	image/x-ms-bmp |\
	image/bmp |\
	image/x-bmp |\
	image/x-bitmap |\
	image/x-xbitmap |\
	image/x-win-bitmap |\
	image/x-windows-bmp |\
	image/ms-bmp)
	bmptoppm "$FW_INFILE" > "$FW_OUTFILE" 2>/dev/null
	;;
	*)
		echo "Unknown file contents. [$MIME]" >&2
		exit 1
	;;
esac

MIME2=`file -b --mime-type "$FW_OUTFILE"`
case $MIME2 in
	image/x-portable-pixmap |\
	image/x-portable-bitmap |\
	image/x-portable-greymap)
	#temporary file created
;;
	*)
		echo "Failed to convert file. [$MIME => $MIME2]" >&2
		exit 1
	;;
esac

exit 0