Cannes, France ? Heath Ledger’s zeal roused his co-stars to up their game in his final film, and his death inspired them — and three A-list friends who completed his role — to carry on with a story the late actor had wanted to see, director Terry Gilliam said Friday.

As Gilliam’s “The Imaginarium of Doctor Parnassus” premiered at the Cannes Film Festival, the filmmaker said Ledger almost co-directed the film.

“Heath was enjoying himself so much, and he was ad-libbing a lot, which I don’t normally allow … but Heath was just brilliant at it, and he got everybody else going,” Gilliam said. “Everybody was just energized by Heath. He was extraordinary. He was almost exhausting because he had so much energy.

“That just passed on to everyone else. Everyone’s part grew because they were full of Heath’s energy,” Gilliam said. “What I thought was interesting was to watch people filling the void that Heath left. Everybody was just growing to make sure that there was no void left in the space that Heath had left us.”

The movie closes with the dedication: “A film from Heath Ledger and friends.”

Ledger’s death by an accidental prescription drug overdose on Jan. 22, 2008, left Gilliam with some of the biggest hurdles he has faced in a career filled with tough breaks. Gilliam fought prolonged battles with studio executives over both “Brazil” (1985) and his previous Ledger collaboration “The Brothers Grimm” (2005).

Gilliam said that, when Ledger died with only about half of his performance for “Doctor Parnassus” filmed, his first thought was to scrap the film.

His solution was to cast Johnny Depp, Jude Law and Colin Farrell to play incarnations of Ledger during otherworldly portions of the fantasy film.

Ledger’s character, Tony, is a slick-tongued fundraiser for children’s charities who crosses Russian mobsters and is left for dead, hanging under a London bridge. He’s rescued by a small theater troupe run by Parnassus (Christopher Plummer), an immortal monk who made a deal with the devil (Tom Waits) and now must find a way to keep the wily demon from taking the soul of his teenage daughter (Lily Cole).