Methods for searching a large face database I have a large face database, and I want to search through it. For example, if I input a new face image, the system would return the best N similarities.

I know that PCA, LDA, and Procrustes analysis are used for this, but it seems that I need to project all this large database into PCA space, and I don't know any library that can handle that. 

Are there some tools, software, or a library for this?
If you can transform your problem into the following "given a set of vectors find the N ones with the smallest euclidian distance to the query", there are well-known methods (Ball-trees, Locality-sensitive hashing...) for solving it on large datasets. With this approach, PCA / LDA is thus just a pre-processing step for transforming the set of features produced by your feature extractor into a lower-dimensionality feature vector.