protected function getFilterOutput($filter, $input)
    {
        if ($filter[0] == '\\')
        {
            $filterClass = $filter;
        }
        else
        {
            $filterClass = '\Slab\Concatenator\Filters\\' . $filter;
        }

        if (!class_exists($filterClass))
        {
            throw new \Exception("Invalid filter class specified: " . $filterClass);
        }

        /**
         * @var \Slab\Concatenator\Filters\FilterInterface $filterObject
         */
        $filterObject = new $filterClass();

        $filterObject->filter($input);

        return $filterObject->getOutput();
    }