Parents: Don’t let your children take out student loans to be studio artists. That’s because computers, which already have proven their ability to beat humans at playing chess and delivering junk mail, now can produce custom oil paintings — or photographs, or pictures in the style of your favorite Chinese dynasty— simply in response to a description. The algorithm underlying this ability, called generative adversarial networks, was published in 2014. But it’s not just math at work — it’s also a database of most of the billions of images available on the internet for a hungry machine to download. That...