Hong Kong animation studio Imagi, which is producing “Teenage Mutant Ninja Turtles” for Warner Bros. and the Weinstein Co., plans to power up “Gatchaman,” a bigscreen adaptation of one of the first Japanese comics to make it to TV as an anime series in the 1970s.Imagi has signed an option arrangement with Japan’s Tatsunoko Prod. Co. for a CG-animated feature. Pic will retain the series’ five caped superheroes, known as the Intl. Science Organization, and pitch them in a new story against their frequent nemesis Galactor. It will be scripted and directed by Kevin Munroe, currently fulfilling those duties on “Turtles.” Production is expected to begin next year. A teaser for “Turtles” will screen at next month’s Comic-Con in San Diego, with the movie expected to open Stateside on March 30. Warner Bros. has North American rights, TWC international.