The photocall was to plug Greatest Days, which is based on hit stage musical The Band.
The show - which features music from Take That - tells the story of a group of women who all loved the same band and were best friends as teenagers, who then reunite 25 years later to see the group perform.
The film is set to star Aisling Bea, Jayde Adams, Alice Lowe, Amaka Okafor and Marc Wootton.
The boy band will feature Aaron Bryan, Dalvin Cory, Joshua Jung, Mark Samaras and Mervin Noronha.
It's thought the band's story will be inspired by Take That, whose music is expected to feature.
Take That's fans said they were thrilled to see them reunited - and that they couldn't wait for the movie.
"OMG!!! IS THIS TRUE???" one said on Twitter.
"Excited!" tweeted another.
"The boys are back in town (Cannes)!" tweeted another fan.
"So good see them together again," said another.
One fan said the snaps made their "heart sing".
"These new @takethat photos are making my heart warm so good to see them together after 3 years," tweeted someone else.
Barlow, Owen and Donald will be executive producers on the film and previously said in a statement: "This is a really exciting time for us.
“We’re really looking forward to working with such a talented and creative team on the film and we’re absolutely delighted to have such a brilliant cast on board.”
Watch: Gary Barlow on FaceTime with Elton John