Privacy advocates cringed when they learned people were being caught unawares by the cameras of Google Street View. That service lets users of Google Maps see photographs of streetscapes - including people milling bout in front of houses and shops.
In response to criticism Google has begun blurring the faces of people on Street View, but that gives the service a strange appearance.
Some researchers at Columbia University believe they have a better way to protect the privacy of people unknowingly photographed by the likes of Google.
Neeraj Kumar and Columbia colleagues have developed software that automatically gives people new faces. The software selects from an image bank of faces, picking the best replacement, then creates a composite face.