protected function execute(InputInterface $input, OutputInterface $output){

		$fontFile = realpath($input->getArgument('font-file'));
		if($fontFile === false || !file_exists($fontFile)){
			throw new \InvalidArgumentException('"'.$input->getArgument('font-file').'" does not exist');
		}

		$outputDirectory = realpath($input->getArgument('output-directory'));
		if($outputDirectory === false || !file_exists($outputDirectory) || !is_dir($outputDirectory)){
			throw new \InvalidArgumentException('"'.$input->getArgument('output-directory').'" is no directory');
		}

		$generator = new IconFontGenerator;

		$output->writeln('reading font file from "'.$fontFile.'" ...');
		$generator->generateFromFont(new Font(array(), file_get_contents($fontFile)));

		$output->writeln('writing SVG files to "'.$outputDirectory.'" ...');
		$generator->saveGlyphsToDir($outputDirectory);

		$output->getFormatter()->setStyle('success', new OutputFormatterStyle(null, null, array('bold', 'reverse')));

		$output->writeln('<success>created SVG files successfully</success>');

	}