Digital Halftoning

Along with text and graphics images are fast becoming a generic datatype for general-purpose computer systems. This poses new problems for the systemsdesigner who must be able to preprocess digital image data for a wide variety ofvideo and hard copy displays. Digital halftoning the method by which the illusionof continuous-tone images are created through the arrangement of binary pictureelements is a key component of any preprocessing.Digital Halftoning addresses theproblem of developing algorithms that best match the specific parameters of anytarget display device. It is the first significant study of the process of producingquality images on practical computer displays.To aid the systems designer Ulichneydevises the concept of blue noise - which has many desirable properties forhalftoning - and suggests efficient algorithms for its use. He also introduces newmetrics for analyzing the frequency content of periodic and aperiodic patterns forboth rectangular and hexagonal grids and presents a unique aspect ratio immunityargument in favor of hexagonal grids. Included are several carefully selecteddigitally-produced images.Robert Ulichney is Principle Engineer with the DigitalEquipment Corporation.