1. A system for classifying an image as a photograph or a graphic, comprising: a memory storing computer-executable instructions of: a component that extracts a prevalent color histogram feature for an image, the prevalent color histogram feature being based on the number of pixels of the image that contain similar colors; a component that generates a ranked prevalent color histogram feature representing an ordering of the colors based on the number of pixels of that image that contain similar colors; and a classifier that classifies the image as a photograph or graphic based on the ranked prevalent color histogram feature, the classifier trained using training data that includes ranked prevalent color histogram features of training images and a label for each training image indicating whether the image is a photograph or a graphic; and a processor for executing the computer-executable instructions stored in the memory.