i am using

This assumes that the global for the current image $_zp_current_image is set:
$maxwidth = 300; $maxheight = 180; getMaxSpaceContainer($maxwidth, $maxheight, $_zp_current_image); $url = $_zp_current_image->getCustomImage(NULL, $maxwidth, $maxheight, NULL, NULL, NULL, NULL, NULL, NULL);