12. The one or more non-transitory computer readable media of claim 11 , wherein the operations further comprise: selecting optimal buckets that are associated with a second label; and training classifiers for the second label based on the selected optimal buckets that are associated with the second label.
13. The one or more non-transitory computer readable media of claim 12 , wherein the operations further comprise adding the classifiers for the first label and the classifiers for the second label to a visual vocabulary.