1. A method comprising: determining, by one or more processors, transitional probabilities between images in a collection of images, a transitional probability being a likelihood that a user, accessing a first image, selects a second image, where the transitional probabilities are based on a conversion operation that relates a particular measure of similarity between the images to a particular transitional probability value; modifying, by the one or more processors, the transitional probabilities to form modified transitional probabilities based on an analysis of documents associated with the collection of images; calculating, by the one or more processors, scores that define a measure of quality for the images, the scores being calculated using the modified transitional probabilities; and providing, by the one or more processors, the images to users in an order based on the scores.