A computationally efficient modeling system for imagery scales both the
original image and corresponding principal component tiles in the same
proportion to be able to extract scaled principal components. The system
includes recovery of feature weights for the image model by extracting
the weights from the reduced size principal component tiles. The use of
the reduced size tiles to derive weights dramatically reduces computer
overhead both in the generation of the files and in the generation of the
weights, and is made possible by the fact that the weights from the
scaled down tiles are nearly equal to the weights of the tiles associated
with the full size image. The subject system thus reduces computation and
the number of bits required to represent features by first scaling the
image and then tiling the image in the same proportion. In one
embodiment, the scaled down tiles are used as training exemplars used to
generate the principal components.