1. A perceptual-segmentation system comprising: a computer; and one or more perceptual-segmentation programs, stored within the computer and executed by the computer, that identify regions within an image; for each identified region, compute or access each of one or more pixel-feature values for pixels within the region, using the one or more pixel-feature values computed or accessed for pixels within the region, compute one or more region-feature values, and using the one or more region-feature values, determine a region type for the region and associating the region type with the region; and store the associations of region types with regions for use in subsequent image-processing tasks.