Ancient masterpiece restored for a modern-day audience, report Wang Qian and Zhu Xingxin in Yuncheng, Shanxi.

Technology, such as artificial intelligence and deep learning, is reshaping the preservation and restoration of cultural heritage, bringing masterpieces back to their former glory and enabling people to appreciate their beauty beyond time and space.

At the UNESCO headquarters in Paris late last month, Fragments of Civilization – Exhibition on the Mural Art of the Yongle Palace displayed one of the latest examples of reviving cultural heritage in the digital era.

Chaoyuan Tu, or the painting of the heavenly court, was the highlight of the exhibition. Using AI technology, experts have brought the mural close to its authentic colors that were used about 800 years ago, making the original features of the mural a present-day reality that can be admired by visitors from around the world.

"In modern times, the restoration of cultural relics is no longer about individual conservators working manually with tools," Xi Jiulong, director of the Yongle Palace mural preservation research institution, said at the exhibition opening in Paris.

"Technological advances are enabling the preservation of cultural heritage. Computing power will ultimately help us reverse time."

A copy of Chaoyuan Tu ("the painting of the heavenly court"), the best-known mural in the Yongle Palace in Yuncheng, Shanxi province, built in the Yuan Dynasty (1271-1368). It features about 300 Taoist figures, depicting a scene of congregation. The vibrant colors of the piece are sharpened by technology. [Photo provided to China Daily]

Divided into five sections – mural art, digital restoration, color exploration, replicas of costumes on the murals and related cultural creative products – the exhibition, which closed late last month, displayed a hand-painted replica of Chaoyuan Tu from the 1980s and an AI-restored version to offer a comparison on how technology has breathed new life into the viewing of ancient murals.

Karalyn Monteil, head of Programmes and Stakeholders Outreach for the Diversity of Cultural Expressions in UNESCO's culture sector, encourages related parties to protect and promote culture in the digital environment, especially in the face of climate change.

Cheng Kun from the Beijing Culture Pieces Development Co, the company behind the exhibition, says that "technology makes it possible to re-create the authentic beauty of the Chaoyuan Tu. Through this exhibition, the Yongle Palace murals, with their unique artistic language, give the world a glimpse into the splendid Chinese culture".

Located in Ruicheng county in Yuncheng, Shanxi province, the mural is the best-known at the Yongle ("eternal joy") Palace, built in the Yuan Dynasty (1271-1368). Known for its approximately 1,005-square-meter frescoes, the Taoist temple complex commemorating Lyu Dongbin, one of the Baxian, the Eight Immortals of Taoism, comprises four wooden structures built along a line running from south to north.

Cheng Kun (left), head of the Beijing Culture Pieces Development Co, displaying a calligraphy piece with Wang Ying, deputy representative to UNESCO for China, at an exhibition on the Yongle Palace in Paris last month. [Photo provided to China Daily]

Measuring 97 meters long and 4.4 meters high, Chaoyuan Tu features about 300 Taoist figures depicting a scene of congregation, which tells a story about Taoist etiquette.

In the mural, the eight main deity figures are as tall as 3 meters. The characters are arranged in four layers from front to back, with various poses including sitting, standing, bending, and facing forward or sideways, in an orderly manner.

"Chaoyuan Tu is considered the crown jewel among existing Yuan Dynasty mural art," Xi says. "The strokes and lines of these murals remain awe-inspiring, but sadly their colors have decayed over time. We don't have a chance to see these murals in their original, vivid colors."

But this situation was remedied when the Beijing Culture Pieces Development Co and US chip design company Advanced Micro Devices planned to cooperate on an AI restoration program for cultural heritage in 2019.

As a Yuncheng native, Cheng, 33, has been fascinated by the exquisite murals in Yongle Palace and, seeing the colors fading, she knew it was time to make her childhood dream come true. Cheng also stresses that human input will always be paramount in art.

Cheng with a visitor at the Yongle Palace last week. [Photo by ZHU XINGXIN/CHINA DAILY]

Jovi Chi, senior marketing director at AMD, says as a tech company, it is their responsibility to preserve and pass down cultural heritage.

In November 2023, the Yongle Palace and AMD joint digital studio was established.

For Fan Aizhu, a mural restorer and inheritor at the palace, the studio helps break the barriers humans cannot cross.

"There are 289 celestial figures in the mural, along with individually unique auspicious animals, religious instruments, costumes and accessories. The palette is extraordinarily diverse and nuanced, making it challenging to capture every detail," she says.

Even with AI, Xu Jinghui, an algorithm expert from Shengshu Technology who provides technological support to the studio, says it is challenging to restore the vivid colors.

Learning from mural experts like Fan, Xu's team has to first scan the painting and then deconstruct it using several steps, such as separating the outline, drawing and coloring. The accurately labeled text and image data is then fed into the AI engine. With the amount of data being fed to AI, the machine not only processes the data related to the mural but also analyzes the discoloration, color fades, damage, cracks and stains that the mural has endured over the last eight centuries.

Part of the original mural that depicts the Jade Emperor. [Photo provided to China Daily]

"AI is like a student and our data annotations are akin to lessons for AI. If we feed accurate information to it, AI can quickly become an expert on mural paintings. This requires that we provide as much accurate data as possible to lead us closer to the original, true colors," Xu says.

For traditional mural conservators, AI has shortened the long and dedicated duplicating period from months to hours.

"Mural restoration and conservation is traditionally done through copying and reproduction. It takes at least 10 years to train a professional mural restorer. Consider the restoration of a main deity as an example – it would take at least a few months working day and night. This can be a cruel test of endurance and patience," Xi says.

Last month, an exhibition to showcase the latest digital restoration results was launched at Yongle Palace, unveiling a virtual docent named Yu Yao whose image is that of a jade maiden beside the Queen Mother of the West, or Xiwangmu, a powerful goddess in Chinese mythology. She can answer questions and interact with visitors.

Xi is happy to see how digital technologies allow the public to access historical knowledge and engage with narratives that were once confined to textbooks and museums and help transform the preservation of cultural heritage.

"We always talk about cultural confidence. How do we build it? We must be able to see the real masterpieces. Advances in technology enable that," he adds.

Contact the writers at wangqian@chinadaily.com.cn