Adobe created Photoshop (first published one) in 1990. I think this was the first one.
Anyway, image manipulation was around before that, and Jerry Uelsmann is perhaps the greatest of those manipulators. He did all his manipulation in the dark room after may years of developing (fair pun) his method. You can see how he did one of his surreal photo composites here:
Photoshop keeps terms like ‘dodge’, ‘burn’ and ‘mask’ whose origins were in photography.
Here are a couple of examples of his work (more at the link below):
Looking at his work gave me a perspective (sorry!) on how Photoshop and image manipulation got their starts and how tools and effects (filters, etc.) were added.
Anyway, some might find it interesting.