Face-hunting software will scour web for targets

17:40 19 December 2006
NewScientist.com news service
Tom Simonite

A search engine that uses sophisticated facial recognition to allow users to identify and find people in online images will launch next month. But civil liberties groups say the biometric-style tool could compromise the privacy of anyone who has their picture online.
Search engine Polar Rose reconstructs the 3D shape of a person's face and then combines that with characteristics of their features to generate a unique "face print". This can then be used to search other photos for a match.

In January users will be able to download a plugin for their browser that allows users to enter information about faces they recognise in online images. This data is then sent to a central server allowing anyone looking at an image containing that particular face print to tell who it is. Users can also search the web for more photos containing that face.

Online image search engines usually work much like their text counterparts. "They find images on pages that contain the words you search for," says Jan Erik Solem, whose PhD project at Malmö University College, Sweden, led to the new company. "Search engines are blind to images, Polar Rose is not."

Third dimension

"Some biometric companies are using 3D laser scans of faces to aid identification from photos," Solem says. "We've developed a way to work backwards; we can create a 3D model of a face from a 2D image."

That allows Polar Rose to recognise people even when the pose or lighting has changed, he says. The technique was developed using a database of around two thousand 3D face-scans paired with normal 2D photos.

"We used statistical methods to work out the relationship between the two," explains Solem. A video on the Polar Rose website (avi format) shows the technique being used to reconstruct actor Tom Cruise's face.

Broadband explosion

The 3D shape is combined with colour and shape data from the 2D picture to generate the face print that serves as a unique identifier.

Solem says he cannot give figures on the search engine's accuracy until it is tested by the public. It works on any image with a face at least 100 pixels (35 millimetres) across, as broadband becomes more common, more and more pictures will fit the bill, he predicts.

Earlier this year, another visual search engine called Riya launched. It has a less biometric approach, instead relying on the context of a person's face – such as clothes and objects around them – to search images for a specific person.

Privacy concerns
Polar Rose and future developments that make facial recognition available to the masses risk encroaching on people's privacy, warns Yaman Akdeniz, director of the UK non-profit group Cyber-Rights & Cyber-Liberties.

"Although this sounds like a great idea, I would not like to be searchable in this way, or so easily tracked without my consent," says Akdeniz. The database compiled by Polar Rose is similar to the kind of biometric database some governments wish to use, he points out.

"I wonder whether they have a right to build such a database," says Akdeniz, he suggests people think twice before embracing such potentially intrusive tools, and consider which photos of themselves they allow online.