1. A system comprising: a buffer to receive compressed sets of pixel data defining parts of rasterized swaths of scan lines of an image of a page, at least one of the parts of one of the rasterized swaths overlapping another part of that swath, the pixel data that defines the overlapping part including mask data that identifies pixels of the overlapping part that are to be included in the image; and circuitry to decompress the sets of pixel data, generate a first series of the rasterized swaths including the pixels identified by the mask data, generate another of the series of rasterized swaths while at least one of the rasterized swaths of the first set are being used by an output device, and use a page description in a form of two levels of linked lists to determine which of the parts to use and in what order to generate the rasterized swaths, an upper level one of the linked lists comprising a list of objects that form the image, the objects being sorted in top-to-bottom order by swaths of scan lines, and, within each swath, in order of overlap from back to front.