Face recognition

I have discovered a new time-sink, and its name is Picasa.

Picasa is a neat little piece of free software which allows you to look at all the pictures on your hard disk. I downloaded it onto my notebook, and have found it very handy for looking through the pictures I take while I'm on holiday.

In fact, I found it so useful that I downloaded it onto my desktop as well. I hoped it would help me to rationalise all the many different folders in which pictures are stashed on my laptop, and maybe get rid of some of the folders I don't actually use. This didn't work out, for two reasons: one, Picasa doesn't actually tell you where it found the image it is showing you; and two - well, there are so very many pictures on my desktop...

But it does have one wonderful feature, labelled 'people'. The software sifts through your pictures and identifies faces, which you then label; thereafter it not only identifies faces, it identifies those faces it has seen before, and files them with the other pictures of the same person. I am not sure which aspect of this amazes me more, the way that it works or the way that it doesn't work.

There's a hypnotic charm in being presented with a screen of thumbnail pictures, and trying to pick out which ones I recognise. Some are clear and sharp, others so pixellated it might have been a deliberate attempt to hide their identity, some so underexposed that all I can see is a faint gleam where the light catches a pair of glasses; some are people I know, some have simply wandered across the background of a tourist location, some are the faces of sculptures, or from a book jacket, and some - very few - are not faces at all (there's a particular configuration of fingers on an accordion keyboard which seems to fool it, though I can't see why). Then, having identified a face as a face, there's the matter of whose face it is. This is genuine living-in-the-future stuff; it's not so long that if we wanted a computer to read numbers from a form they had to be printed in a particular font - now my computer can make a decent stab at identifying individual faces! It slips up, of course, from time to time, as we all do. For a while it was persuaded that durham_rambler and GirlBear were the same person, but it has learned otherwise. And it does seem to learn: the more examples of a given face it knows, the more confidently it recognises further pictures of the same face (confidently is not synonymous with correctly, but there is a comfortable overlap).

Alongside the marvels of the computer's memory. the process illustrates the limitations of mine. Why does it take me so long to recognise people I know perfectly well? Why do I forget the names of people I recognise? Why do I forget which thumbnails I have already double-clicked (to see the full image) and still can't identify? Why don't I know how some of these pictures got onto my hard disk? The full cast of Heartbeat fair enough, that's work related, but where did these two pictures of Terry Pratchett come from?

As I said, hours of fun for all the family...