1. A method comprising: determining, by a computing device, an image gradient representation of each digital image of a plurality of digital images, the image gradient representation identifying a plurality of image gradients determined for the digital image; building, by the computing device, a vocabulary of words using the image gradient representation of each digital image of the plurality of digital images; determining, by the computing device and for each digital image of the plurality, a frequency of occurrence of each word, of the vocabulary of words, using the image gradient representation of the digital image; generating, by the computing device and using the vocabulary, a probabilistic topic model comprising image-specific parameters for each digital image in the plurality of digital images and cluster-specific parameters for each cluster of a plurality of clusters; assigning, by the computing device, each digital image from the plurality of digital images to a cluster of the plurality of clusters using the digital image's image-specific parameters, the frequency of occurrence of each word associated with the digital image and the probabilistic topic model, each cluster corresponding to a word in the vocabulary; identifying, by the computing device and for each cluster of the plurality of clusters, a representative digital image for the cluster; receiving, by the computing device, a digital image search request of a user; generating, by the computing device, a set of words, from the vocabulary of words, for the received digital image; identifying, via the computing device and using the set of words generated for the received image as a query, a number of representative digital images, each representative digital image of the number being representative of a cluster, of the plurality of clusters, associated with at least one word of the set of words generated for the received image; and communicating, via the computing device, the number of representative digital images to the user for display on a device of the user.