Hynopompic Hallucinations and hynagogic imagery are two very different variations of consciousness.
as stated in you topic title HH your eyes are open. Otherwise it would be a dream scene rather then a hallucination.
HI on the other hand most often always will occur while your eyes are shut. These are images that precede the images in a dream.
HI is usually before sleep. HH is often after a dream and in conjunction with sleep paralysis. Which is also often mistaken for alien abductions. seriously!