public function getPortraitFile($size)
    {
        $filename = $this->filename;

        //get file extension
        $extension = explode('.', $filename);
        $extension = array_pop($extension);

        //remove extension
        $name = preg_replace('#\.[^.]*$#', '', $filename);

        $filename = $name.'_'.$size.'.'.$extension;

        return $filename;
    }