1. A method of processing a pixel of a digital image, the method comprising mapping intensity of the pixel as a smooth, non-linear continuous function of the intensity and minimum and maximum intensities of a local pixel neighborhood of the pixel if the intensity is within a local contrast range; wherein the mapping function also allows for selective thickening of dark features; and wherein the mapping function is non-decreasing, produces filtered values that do not exceed the local contrast range, and identity-maps the minimum and maximum values; and maps a point lighter than a mid-range point by a prescribed amount to the mid-range point.