1. A method implemented on a computing device having a processor for summarizing image search results, comprising: using the computing device having the processor to perform the following: estimating an image relevance for each image in the image search results as a ranking of each image given by a search engine that provided the image search results in response to a query from a user to the search engine; computing an image quality for each image based on one or more image quality measures; clustering images in the image search results using a clustering technique that has as a first informative prior the image quality for each image and as a second informative prior the image relevance for each image to obtain a summary candidate collection containing image clusters and an exemplar image for each cluster; selecting and ranking each image in the summary candidate collection to obtain an image search results summarization; selecting a number representing a desired number of summaries; and presenting the image search results summarization to a user based on whether a number of images contained in the image search results summarization is less than the number representing a desired number of summaries.