Melting 'frozen memories,' AI helps Japanese recall war days

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This photo combination shows digital colorization, left, by Anju Niwata and Hidenori Watanave, and original black and white file photo that smoke rises around 20,000 feet above Hiroshima, Japan, after the first atomic bomb was dropped on Aug. 6, 1945. Niwata and Watanave are adding color to pre-war and wartime photographs using a combination of methods. These include AI technologies, but also traditional methods to fill the gaps in automated coloring. These include going door to door interviewing survivors who track back childhood memories, and communicating on social media to gather information from a wider audience. The team has brought to life more than a thousand black-and-white photographs that illustrate the pre-war lives of ordinary people and chronicles the onset and destruction caused by World War II. (Anju Niwata & Hidenori Watanave via AP)

TOKYO – When Tokuso Hamai saw the colorized version of an old black-and-white photo of a picnic held under cherry tree blossoms sometime before World War II, forgotten memories of family members, most of whom died in the atomic bombing of Hiroshima in 1945, came pouring out.

“In colorized photos, people come to life,” said Hamai, now 86. “I often played near (the picnic site), and sometimes I would do some naughty things and get scolded by my father.”

The power of a colorized photo to reignite lost memories was eye-opening for Anju Niwata, a student who gave Hamai the colorized photo as a present three years ago.

The 75th anniversary of the end of World War II is Saturday, and Niwata, now 18, said she hopes it will bring attention to her project with a Tokyo University professor to painstakingly colorize photos using artificial intelligence and their own research to spark lost memories for the rapidly aging generation who experienced the war.

“Seeing Niwata share the colorized pictures with Hamai, and then watching him recall his old memories one after another, made it feel like the ice around his frozen memories was melting away,” said Hidenori Watanave, the professor who taught Niwata how to colorize monochrome pictures using AI.

Niwata and Watanave call their photo colorization project “Rebooting Memories,” and they published a book last month of the colorized versions of about 350 monochrome pictures taken before, during and after the war.

Watanave and Niwata use three different types of AI photo coloring software. The AI is useful in identifying the accurate colors of natural things, such as the sea, the sky and human skin, but it cannot accurately colorize human-made objects like roofs and clothes, Watanave said.

So Niwata and Watanave painstakingly finish the AI-colorized photos by hand to get more accurate colors based on the photo owners’ memories and advice from experts. They also look through historical documents and archives that show what the colors should look like.