public function blob( $type = 'PNG' ) {

        $type = strtoupper($type);
        if ( ImageType::GIF == $type ) {

            imagegif( $this->gd );

        } else if ( ImageType::JPEG == $type ) {

            imagejpeg( $this->gd );

        } else if ( ImageType::PNG == $type ) {

            imagepng( $this->gd );

        } else if ( ImageType::WBMP == $type ) {

            imagewbmp( $this->gd );

        } else {
            throw new \Exception( sprintf( 'File type "%s" not supported.', $type ) );
        }
    }