bitmap data likeness algorithm

I'd like to compare two bitmaps or parts of bitmap and see how alike they are.

I've came across some likeness algorithms for string data, like Levenshtein distance, and Jaro–Winkler distance. these, obviously, do not help when it comes to bitmap data.

Can anyone s开发者_C百科uggest an algorithm for comparing how alike bitmaps are?

EDIT

Thanks for the ideas,links etc.

While all information is helpful in familiarizing with this topic, I'm wondering how to generate images, something more along the lines of this:

You could use Hausdorff image comparison, but be aware that this expects binary images.

Of note, visually similar images may have vastly different underlying pixel representations. Human perception makes computing visual similarity quite difficult. Hausdorff deals well with this by allowing two different images to score highly when the general similarity is the same.

If you want to compute data distances, you can use any distance metric you like and do so directly on the pixels. I'm particularly fond of Mahalanobis distance for these kind of comparisons.

Here's an interesting link from a similar question. Using a self training neural net to recognize similar images.

You want to use a Hilbert Curve to subdivide the image and read the rgb values. Then you can use a Fast Fourier Transformation to record the image into a discrete analog signal. Then you can store this into a database and compare it with other results. The results should be very good. In fact this is like the Quantiziser step in the JPEG compression (hilbert curve) except that the JPEG compression uses a Morton Curve.

Neural networks also bring solution. You can use Kohonen network (it will group your images into classes and give topological map of them) or use Hopfield network (provide some representative images and after learning procedure images will be classified by network to images provided in learning mode).

Kohonen networks: http://en.wikipedia.org/wiki/Self-organizing_map

Hopfield network http://en.wikipedia.org/wiki/Hopfield_network