BEIJING — The Chinese box office is predicted to produce a bumper harvest in 2012, with total grosses forecast to exceed 20 billion yuan ($3.17 billion), an industry research group said in a report.Last year, B.O. totalled $2.08 billion, EntGroup, a provider of information on the Chinese biz, said. Film industry revenues are forecast to total $4.6 billion this year, compared with $2.82 billion last year. Non-B.O. revenues were $410 million, while the take from overseas revenue was $320 million. The strong rise in the Chinese biz has prompted massive interest from overseas companies in gaining access to this lucrative but difficult market. Earlier this week, News Corp. bought a 20% stake in one of China’s top private shingles, Bona Film Group. Much of the rise of the Chinese film biz has been based on a big jump in the number of screens, as the real estate boom feeds into widescale theater construction. Entgroup is forecasting a 28% rise in screen numbers for 2012 to 11,800, while the number of theaters is expected to rise 20% to 3,370. This marks a slowdown from last year, when the real estate sector was really cooking, prompting regulators to tighten bank credit for real estate developers alongside other cooling measures. Last year, the number of screens rose 47% to 9,200, while the number of cinemas rose 40% to 2,800. Entgroup is also anticipating a rise in the number of initial public offerings because of the strong rise in the market. Big names in the biz like Huayi Brothers, Bona and Enlight have already listed on stock exchanges. “The rapid expansion of China’s film market and the government’s efforts to promote the market, means many film- related companies are seeking IPOs for the future development and to gain profits,” Entgroup said in a statement.