7. A system, comprising: a data store; one or more computing devices executing within a network and performing operations to: access, from a data source of images external to the network, image data related to a specified category; identify, based at least in part on the image data, subcategories of the specified category; generate a knowledge base (KB) that includes individual ones of the subcategories; store the KB in the data store; obtain, from at least one of the data source of images external to the network or an alternative image source, digital images for the subcategories, the digital images identified based, at least in part, on the KB; train an image classifier using the digital images and the KB; receive an image; and classify the image into a one of the subcategories using the image classifier.
7. A system, comprising: a data store; one or more computing devices executing within a network and performing operations to: access, from a data source of images external to the network, image data related to a specified category; identify, based at least in part on the image data, subcategories of the specified category; generate a knowledge base (KB) that includes individual ones of the subcategories; store the KB in the data store; obtain, from at least one of the data source of images external to the network or an alternative image source, digital images for the subcategories, the digital images identified based, at least in part, on the KB; train an image classifier using the digital images and the KB; receive an image; and classify the image into a one of the subcategories using the image classifier. 8. The system of claim 7 , wherein the data source of images external to the network comprises a structured data source and identify subcategories of the specified category is based on a structure of the structured data source.