Multidimensional indexing of images

I would like to know if there is a good way for indexing multidimensional objects (i.e. images). More precisely, I have a large collection of images on which I calculate n-dimensional feature vectors. There is a distance metric (i.e. L2-norm) defined over those feature vectors d(u,v). Given a key (an n-dimensional) k, the index should allow fast retrieva开发者_开发技巧l of feature vectors that are "close" to k (that is, their distance is small).

MATLAB code reference would be great...

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For distances r-tree's are often used. I think it can apply to n-dimensions, but I'm not sure if it will work with custom distance or dissimilarity functions. I think it's implemented in this library. It might help to convert your data to n-dimensional coordinates.