Eagle - export image of holes for component leads
Usually drill machines use Excellon drill files.  There are various ULPs and CAM processor jobs that come with Eagle to make it easy to export such files.  That's what I've always done and never had a board house complain or put drills in the wrong place or with wrong diameters.

Excellon is such a standard that whatever your drill machine is, it probably at least has software that can convert from Excellon format to whatever it uses internally.  A PNG file is a image, which doesn't make any sense for communicating drill information to a drill machine.