Electronic Screening at Arbitrary Angles and Rulings

A new method for electronic screening at arbitrary angles and rulings is presented. It is based on a new digital representation of halftone images. A formal mathematical formulation within the framework of digital geometry is given, encompassing some variations and generalizations. In extension of this, analysis of digital methods of processing halftones is given. Incorporating number theory, the analysis focuses on digital implementations and Moire and shadowing problems in this connection. The method is suited for parallelization, it has been implemented on a transputer-system. Experiments on artificial and real test images have been carried out giving promising results. A sample of these are shown. The method performs as a look-up table screening method. It uses sub-dots but compared to other look-up table screening methods with the same sub-dot resolution, the dots are more regular. In comparison with threshold screening, it renders a smoother image, whereas threshold screening is better at rendering line work. Extensions to improve the ability of rendering line work are given.