If you've seen the previews for "Hangover 2" -- you already know Ed Helms wakes up with a Mike Tyson face tattoo ... but now, the guy who did Tyson's ink is PISSED at producers, claiming they ripped off his work without permission.

The guy who applied Tyson's face tattoo back in 2003 is S. Victor Whitmill -- who claims he not only created the design, but copyrighted it as well.

In fact, Whitmill says he's never allowed ANYONE to use the image since he put it on Tyson.

Now, Whitmill has filed a lawsuit in federal court in St. Louis, claiming Warner Bros. -- the studio behind the movie -- violated his copyright ... and he wants to block the studio from showing the tattoo in the film.

Whitmill is also demanding an unspecified amount of cash.