1. A non-transitory storage medium storing instructions executable by a processor to perform a method comprising: extracting local descriptors from an image; generating an image vector having vector elements indicative of parameters of mixture model components of a mixture model representing the extracted local descriptors; and compressing the image vector using a vector quantization algorithm to generate a compressed image vector by operations including splitting the image vector into a plurality of sub-vectors wherein each sub-vector includes at least two vector elements and each sub-vector includes only vector elements indicative of parameters of a single mixture model component, compressing each sub-vector independently using the vector quantization algorithm, and concatenating the compressed sub-vectors to generate the compressed image vector.