At first glance, “Blancanieves” looks like a gimmick: It’s a Spanish film based loosely on the story of Snow White, and it’s photographed to resemble a black-and-white silent film from the earliest days of narrative cinema. But, like 2011’s mostly silent Best Picture winner “The Artist,” this is the case of convention breeding invention, and director Pablo Berger is artistically liberated by his techniques when most filmmakers would be shackled by them. Spain’s official selection as Best Foreign Film for this year’s Oscars (it wasn’t nominated), “Blancanieves” begins in the tradition of grand, lurid melodramas. In 1920s Seville, a famed bullfighter is gored in the ring, and his pregnant wife goes into labor as she looks on. She dies giving birth, and her husband, now paralyzed, rejects his newborn daughter in grief.