"Tip: As with anything that outputs its result directly to the browser, you can use the output-control functions (http://www.php.net/manual/en/ref.outcontrol.php) to capture the output of this function, and save it in a string (for example)."

ob_start();
imagepng($image);
$image_data = ob_get_contents();
ob_end_clean();

And now you can save $image_data to a database, for example, instead of first writing it to file and then reading the data from it. Just don't forget to use mysql_escape_string...