Although their involvement in "The Dark Tower" pretty much had been taken as a given, Stephen King made it official this morning: Idris Elba and Matthew McConaughey will star in the long-brewing adaptation of the author's fantasy epic.

As previously reported, Elba will star as gunslinger Roland Deschain, while McConaughey will play the villainous sorcerer the Man in Black. They'll be joined by "Mad Max: Fury Road" actress Abbey Lee as Tirana.

Director Nikolaj Arcel, who wrote the screenplay with Anders Thomas Jensen, Akiva Goldsman and Jeff Pinkner, told Entertainment Weekly production will begin in seven weeks  in South Africa.

Contrary to earlier reports, King said the film won't adapt his 1982 novel "The Gunslinger" (the first novel in the "Dark Tower") series, but rather "starts in media res, in the middle of the story instead of at the beginning, which may upset some of the fans a little bit, but they’ll get behind it, because it is the story."

He added, “A lot of it takes place in our day, in the modern world.”

The ambitious adaptation, which calls for a movie trilogy and interlocking television miniseries, was abandoned in 2011 by NBC Universal following delays over the budget, only to be shopped around for years by producer Imagine Entertainment as it sought new financing and a new home. Sony Pictures and Media Rights Capital finally stepped up in April, announcing this first film, which is set for release on Jan. 13, 2017.