protected function getBinaryBuffer() {
		// catch the GD2 output
		ob_start();

		// convert a (probably) color/greyscale image to the monochrome counterpart.
		imagewbmp($this->image);

		// catch contents of the WBMP file.
		$wbmp = ob_get_clean();

		// ignore 2 bytes of WBMP file header
		$i = 2;

		// ignore 2 VLQ's (variable-length quantities) describing WBMP resolution.
		for($j = 0; $j < 2; ++$j) {
			do {
				$test = ord($wbmp[$i]) & 0x80;
				++$i;
			} while($test);
		}

		// return binary buffer as a string of chars (bytes)
		return substr($wbmp, $i);
	}