German-Jewish artist Charlotte Salomon, who was murdered in Auschwitz at age 26, and her autobiographical masterwork “Life? or Theatre?,” which was created in a two-year burst in the early 1940s, are the subjects of “Charlotte,” a unique animated biopic drama that marks a career turning point for Toronto producer Julia Rosenberg.

Rosenberg first encountered “Life? or Theatre?” — which comprises hundreds of gouache paintings, a 32,000-word journey-of-an-artist tale filled with dark family secrets and numerous text overlays and music cues — as a bat mitzvah gift. She soon developed “a very possessive personal relationship” with the book. “It’s the book I would buy and give when I fell in love,” she said.

After a decade racking up producer credits on notable Canadian dramatic and documentary features, Rosenberg decided one morning in 2012 that an animated film should be made of Salomon’s life, and set about harnessing her passion and wide network to make it so.

“Charlotte,” a Canada-France-Belgium co-production directed by Eric Warin (“Ballerina”) and Tahir Rana (“Welcome to the Wayne”), receives its world premiere in Toronto’s Special Presentations Sept. 13. Same-day buyer screenings are being held in L.A. and New York theaters. The film is distributed in Canada by Elevation Pictures and MK2 Mile End; Sierra Affinity is handling U.S. and international sales.

Keira Knightly and Marion Cotillard deliver, respectively, the English and French performances of Charlotte, and also serve as executive producers.

“I believe this film is going to connect with young creative women. It’s a war story, it’s a refugee story, but it’s really a biopic of an artist who’s been overlooked. She invented the graphic memoir, he played with autofiction and did all of these conceptual things that are now widely used. She’s one of the great artists of the 20th century,” said Rosenberg, an opinion shared by Salomon scholars and fans.

While Rosenberg now has three animation projects, including a hybrid series set in the world of assassins, on her development slate, “Charlotte” was her first. The learning curve was steep.

“I was blissfully ignorant of how animation is normally developed, which is through storyboarding,” she recalled. “Not knowing that, I developed this as I would a live-action film and spent four years working on the screenplay with Erik Rutherford, who did a lot of very heavy lifting. Then writer David Bezmozgis came on and worked on geometrically refining the character development — it was a lovely collaboration.”

Some of the early writing work did inform the visual side. “We made some choices related to details we knew or found out. Salomon never used the color black and so we knew that we would never use it in the film,” she said. 

Animation vet Christina Rotsaert was Rosenberg’s main ally in building the animation team. “We found Tahir Rana who had developed the technique of 2D realism combined with 3D for a television series, and that allowed us to keep moving forward.”

Another key ally was U.K. casting director Kate Rinzell, who helped assemble the top-tier voice cast, a key component in securing gap financing. “We were incredibly fortunate to get Keira Knightly — it’s her first feature animation role — and after she came on board everybody said ‘yes.’ It’s unusual for actors to be invited to perform in an animated film that’s not a comedy.”

The English vocal performances were recorded in London over five days, with Knightly performing her scenes with Jim Broadbent (Charlotte’s grandfather) and Mark Strong (one of Charlotte’s love interests) opposite the actors.

“My feeling is that whoever distributes the film will market it like an independent film, which is why we’re lucky to have an incredible cast,” said Rosenberg. “In terms of awards it’s animation, but in terms of marketplace, we’re competing with other independent live-action films.

“I’m dying to see (animated documentary) ‘Flee,’” she continued. I’m happy ‘Charlotte’ is arriving at a time when we’re not the only ones saying, hey, this is not a cartoon, OK?”

On the live-action front, Rosenberg and Robert Lantos of Serendipity are producing “Maya and Samar.” Anita Doran (screenwriter of “The Breadwinner”) will adapt Tamara Faith Berger’s screenplay about a young journalist whose preconceptions are revealed to her through her acquaintance with a queer woman who lives without status in a foreign land.

Rosenberg produced the film with Jerome Dopffer of France’s Les Productions Balthazar, and Eric Goossens and Anton Roebben of Belgian animation studio Walking the Dog. Executive producers include Nancy Grant, Xavier Dolan, Robert Lantos, Jim Sternberg, Joe Iacono, Mark Musselman, Morgan Emmery, Jean-Charles Levy, Cedric Iland, Bastien Sirodot, Knightly and Cotillard.