We address the problem of large scale image search, for which many
recent methods use a bag-of-features image representation. We shows
the sub-optimality of such a representation for matching descriptors
and derive a more precise representation based on 1) Hamming embedding
(HE) and 2) weak geometric consistency constraints (WGC). HE provides
binary signatures that refine the matching based on visual words. WGC
filters matching descriptors that are not consistent in terms of angle
and scale. HE and WGC are integrated within an inverted file system
and are efficiently exploited even in the case of very large
datasets. Experiments performed on a dataset of one million of images
show a significant improvement due to the binary signatures and the
weak geometric consistency constraints, as well as their
efficiency. Estimation of the full geometric transformation, i.e., a
re-ranking step on a short list of images, is complementary to our
weak geometric consistency constraints and allows to further improve
the accuracy.