public function getImageDimension($columnClass)
    {
        switch ($columnClass) {
            case "grid-md-12": // 1-col
                $this->thumbnailSize = array(1200, 900);
                return $this->thumbnailSize;

            case "grid-md-6": // 2-col
                $this->thumbnailSize = array(800, 600);
                return $this->thumbnailSize;

            default:
                $this->thumbnailSize = array(400, 300);
                return $this->thumbnailSize;
        }
    }