1. A method for managing images, comprising: selecting, from a storage device, an image included in an image library for which an image index is to be generated; determining at least one target region included in the image; extracting a set of one or more visual features from the determined at least one target region; determining, using one or more computer processors, a similarity value of the selected image and another image included in the image library based on the extracted set of visual features; determining image categories to which the images included in the image library belong, based at least in part on the determined similarity value of the selected image and the other image; and assigning category identifiers to the images included in the image library, wherein a same category identifier is assigned to images belonging to a same image category, and different category identifiers are assigned to images belonging to different image categories.