1. A method of analyzing a digital image to determine an unordered local descriptor describing the digital image, the method comprising: selecting a subset of feature points within multiple local extrema, wherein each feature point has an associated blur level and scale octave; creating a vector for each of the feature points, each feature point vector based on the normalized intensity values of a patch around the feature point, wherein the patch size is determined by the associated octave; dividing the patch into multiple overlapping patches, wherein each overlapping patch is represented by a vector; concatenating each overlapping patch vector by projecting the multiple overlapping patch vectors onto an eigen space; and creating an unordered local descriptor for the digital image, wherein the unordered local descriptor is a compact representation of feature points defining the digital image, and wherein the compact representation is a multi-vector descriptor formed from the concatenated patch vectors.