Add this to the beginning of the function:
`
global $_zp_gallery, $_zp_current_album, $_zp_current_image, $_zp_current_zenpage_news,
$_zp_current_zenpage_page, $_zp_gallery_page, $_zp_current_category, $_zp_authority;
`
Then change your getImageTitle line to this:
`
if(is_object($_zp_current_image)) $item_name .= gettext('; Photo: ').$_zp_current_image->getFileName();
`