The three companies previously partnered on Imagi's first theatrical production, TMNT, which opened in March 2007 at the top of the US box office.
Details of the new deal are still being finalised. On TMNT, Warner Bros handled the North American release, and some other territories including Japan, Italy, Spain and China, while TWC handled international sales.
The deal was announced by Warner Bros Pictures president of production Jeff Robinov, TWC co-founder Harvey Weinstein and Imagi co-CEOs Douglas Glen and Francis Kao, and brokered by The William Morris Agency.
'Imagi is breaking new ground with big action pictures done entirely in CG animation,' said Robinov. 'It's an exciting new genre, with the potential of attracting big mass market audiences.'
'TMNT had the kind of beautifully choreographed action sequences you'd expect from Hong Kong animators,' said Weinstein. 'The next two films will confirm Imagi's reputation as the world's leading action hero animation studio.'
Gatchman , scheduled for release in early 2009, originated in Japan in the early 1970s as the TV series Science Ninja Team Gatchaman, which aired in the US as Battle Of The Planets and G-Force.
TMNT director Kevin Munroe will direct the Imagi feature-length version with Lynne Southerland producing.
Scheduled for release later in 2009, Astroboy was originally created by Japan 's 'god of manga' Osamu Tezuka in the early 1950s. Colin Brady (Toy Story 2) will direct the feature, with Maryann Garger as producer.