Wish you had a Mona Lisa smile? A face like a fox? Well, now you can change it, at least on your iPhone.

Yahoo Japan has released Face Stealer, an iPhone app that maps images of faces onto your own. The app scans an image of a face — it doesn’t have to be a photograph — and logs where certain features such as the mouth, nose and eyes are. You then use the touch screen to alter the contours of the face, perhaps by making it a bit wider or taller, to better match yours.

When the phone’s video camera is turned on, the app superimposes the new face on the old. So you can look like George Washington or the Mona Lisa. It even works with animals, and Yahoo Japan has a whole library of images for people to choose from. On top of that, it tracks the movement of the face, showing different expressions and following lip movement when talking.

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Face-tracking software that makes “masks” has appeared in movies such as Avatar and The Lord of the Rings — it made actors look like the alien Na’avi and Gollum. That software uses a lot of computing power, and the actors had to wear tiny tracking “dots” on their faces to feed the computers data. Face Stealer brings that technology into the consumer market, and it tracks the face in real time without the dots.

The effect is a bit surreal (somehow I am reminded of the Joker’s flesh-mask) since the matchup isn’t perfect, but it’s not hard to picture it getting better in future iterations. Yahoo Japan plans to release a version that could work with apps such as iChat, so you can wear a different face while having a conversation.

Aside from aspiring move-makers, this has a lot of interesting implications for privacy. As the software gets better, it will let people hide their faces even on video chats. A sufficiently faithful reproduction of a face could make it that much tougher to tell if the person calling really is who they say they are.

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Yahoo Japan engineer Issei Yoshida told Diginfo TV that since the software can track facial expressions, it should be possible to transmit those expressions with a generic image (like a cartoon) so that you can show facial expressions without anyone seeing what you look like — kind of a souped-up version of emoticons.

If nothing else, it may give a whole new dimension to crank calls.

See a video here.

Via Diginfo TV, iTunes

Credit: Yahoo Japan