public function getCoverFile($size)
    {
        $coverFilename = $this->coverFilename;

        //get the extension
        $extension = explode('.', $coverFilename);
        $extension = array_pop($extension);

        //remove file extension
        $name = preg_replace('#\.[^.]*$#', '', $coverFilename);
        $coverFilename = $name.'_'.$size.'.'.$extension;

        return $coverFilename;
    }