image matching algorithms

[Daniel Fetchinson]

Hi all,

There are a number of free tools for image matching but it's not very
easy to decipher the actual algorithm from the code that includes db
management, GUI, etc, etc. I have my own image database and GUI so all
I need is the actual algorithm preferably in pseudo code and not in
the form of a research paper (from which I also found a lot but since
I'm not that much interested in the actual science of image
recognition this seems like an over kill).

My understanding of image matching is that it works by first
calculating N real numbers for an image and defining a metric for
pairs of N-tuples. Images are similar if their distance (defined by
the metric) is small.

The various free tools differ by their chosen optimization paths and
their degree of specialization. My preference would be,

1. Doesn't really matter how long it takes to compute the N numbers per image
2. Lookups should be fast, consequently N should not be too large (I guess)
3. It should be a generic algorithm working on generic images (everyday photos)
4. PIL should be enough for the implementation

So if anyone knows of a good resource that is close to being pseudo
code I would be very grateful!

Cheers,
Daniel