17. The method of claim 16 in which the image data include, for each location in the image, a respective data item; the substep of applying the criterion including a substep of accessing the respective location's data item.
17. The method of claim 16 in which the image data include, for each location in the image, a respective data item; the substep of applying the criterion including a substep of accessing the respective location's data item. 18. The method of claim 17 in which each location's data item indicates whether the location has a first color or a second color, the substep of applying the criterion further comprising a substep of determining whether the respective location's data item indicates that the respective location has the first color.