China’s booming box office and seemingly inexhaustible cash reserves have provided a much-needed boost to Hollywood as it faces slowing ticket sales in the United States and challenges from Amazon and Netflix.

But Hollywood’s embrace of China has not come without strings attached.

So when the creators of “Pixels” wanted to show aliens blasting a hole in the Great Wall of China, Sony executives worried that the scene might prevent the 2015 movie’s release in China, leaked studio emails show. They blew up the Taj Mahal instead.

In the 1960s, Marvel Comics introduced a mystical guru character known as the Ancient One into its universe. He was portrayed as an elderly Tibetan man.

But in the 2016 movie “Doctor Strange,” the Ancient One is Celtic, played by the white actress Tilda Swinton. Moviemakers decided to change the character’s ethnicity early in the process, reportedly to avoid offending the Chinese government.

As recently as two decades ago, major Hollywood movies were sharply critical of China. “Seven Years in Tibet,” which depicts Chinese soldiers brutalizing Tibetans, was one of the top 100 grossing movies of 1997. Also that year, Disney released Martin Scorsese’s “Kundun” — a sympathetic portrayal of the Dalai Lama’s early life in Mao-era China and his subsequent exile in India — despite objections from the Chinese authorities.

“You’re not going to see something that’s like ‘Seven Years in Tibet’ anymore,” said Larry Shinagawa, a professor at Hawaii Tokai International College who specializes in Asian and Asian-American studies. Studios that make films critical of China, he said, risk being banned from releasing movies in the country.

At stake for China is more than just the validation of Hollywood’s powerbrokers and celebrities. In speeches and at forums, President Xi Jinping has repeatedly emphasized the need to “tell China’s story well” — to make sure a coherent, compelling and, most important, Communist Party-sanctioned narrative of China’s rise to power reaches global audiences.

“There is a notion that its propaganda has not worked well enough,” said Orville Schell, the director of the Center on U.S.-China Relations at the Asia Society. “So this is where the film industry comes in. There’s a real sensitivity to the blockbuster power of Hollywood.”

China has raised its influence in Hollywood by bankrolling a growing number of top-tier films.

Hollywood studios are also eager to grab a slice of China’s fast-growing box office market, which surpassed the United States’ in total revenue for the first time ever in the first quarter of 2018.

Success in China can make up for a disappointing box office performance at home or even transform a hit into a global blockbuster. By the same token, getting shut out of the Chinese market can be devastating for a movie.

That’s a powerful incentive to avoid causing any offense to China.

One of China’s top movie regulators spelled it out in a speech at the U.S.-China Film Summit in Los Angeles in 2013.

“We have a huge market, and we want to share it with you,” said Zhang Xun, then the president of the state-owned China Film Co-Production Corporation, speaking to a room full of Hollywood executives.

Then came the condition. “We want films that are heavily invested in Chinese culture, not one or two shots,” she said. “We want to see positive Chinese images.”

China’s campaign to push a positive image abroad has extended beyond Hollywood.

The 2016 film “The Great Wall,” a $150 million China-Hollywood co-production starring Matt Damon, was China’s highest-profile attempt to make a crossover hit. It was, by most measures, an international flop.

Since then, China has stepped away from the big-budget co-production model, focusing instead on making features that cater to its large and still-expanding domestic market. To do that, it has enlisted Hollywood talent — producers, technical experts and even top celebrities.

But they have had to walk a fine line.

A number of actors, musicians and other celebrities have been barred from entering the country over behavior deemed inappropriate or critical of the Chinese Communist Party.

Perhaps most central to China’s soft power push is CGTN, the international arm of the state broadcaster CCTV. With employees from more than 70 countries and regions working on television channels broadcasting in English, Spanish, French, Arabic and Russian, CGTN’s mission is to report news for global audiences “from a Chinese perspective.”

The difference in the “Chinese perspective” was most evident in CGTN’s coverage this year of an unexpected proposal to abolish presidential term limits in China’s Constitution. While Western news media outlets raced to explain why the amendment, which would open the door to President Xi’s indefinite rule, was unprecedented, CGTN’s anchors were calm — and eerily synchronized — in their message praising the change.

It is difficult to tell whether China’s push to soften its image through movies, media and cultural projects has been successful.

“Chinese soft power has not been that successful outside of the developing world,” said Stanley Rosen, a professor at the University of Southern California who studies Chinese society and cinema. “If China does have any soft power, it’s probably because of the success of their economy and the Chinese model that they’re pushing very hard now.”