Methods for applying full color graphic decals to the surface of a 3d printed part? I'm trying to find a way of applying graphics to my ABS printed parts. 

I need a robust method which can produce a decent amount of detail with true color and legible fine text .
I also was hoping to avoid the use of stickers and opt for something that's slightly more permanent. 

I was wondering if there are ways in which a vinyl decal or other types of decal material could be pressed into the face of a plastic part and then thermally fuse the two layers together using heat transfer method?

Most of the surfaces I work with would be flat, but there are some parts that are slightly curved and it would be totally amazing if I could somehow apply graphics to those areas as well.

Thanks for any hints
Industry has for years used a 'pad printer' to put images on complex shapes, like plastic or ceramic travel mugs, etc.

I have observed these, but never used one.  I see no reason why there couldn't be a DIY version made.

Best of luck, and I look forward to seeing what you come up with!