Mathematical calculations performed by computer software in the production of digital halftones. The algorithms essentially convert the pixels of each process color of the digital image—which are stored as gray values—into halftone dots (or, more accurately, halftone cells) of a particular shape, size, and screen angle. Different systems utilize different screen algorithms to effect the conversion of digital halftones, and many are proprietary. For many years, one particularly sticky problem was irrational screen angle calculation. See Screen Angles.