9. The method of claim 5 , where filtering the plurality of images comprises: determining whether a file format for a particular image of the plurality of images comprises a particular image file format, and discarding the particular image when the file format for the particular image is not the particular image file format.
5. The method of claim 4 , where the document includes a plurality of images, where the plurality of images include the representative image, and where the method further comprises: filtering the plurality of images to eliminate one or more images, of the plurality of images, from being selected as the representative image for the cluster.