In an image segmentation system that processes image objects by digital filtration, a digital filter is defined. The digital filter includes a neighborhood operator for processing intensity values of neighborhoods of pixels in a pixel array. A first pixel array is received defining a pixelated image including one or more objects and a background and a second pixel array is received that defines a reference image. The reference image includes at least one object included in the pixelated image in a background. In the reference image, pixels included in the at least one object are distinguished from pixels included in the background by a predetermined amount of contrast. Pixels of the first and second images are compared to determine a merit value; the merit value is used to compute neighborhood operator values; and, the neighborhood operator is applied to images in order to create or enhance contrast between objects and background in the images.