We present techniques for rendering high-quality color text and graphics on a laser printer using pulse-width modulation (PWM). Multilevel tones for these printers are generated using a combination of screening and pulse-width modulation signals that switch a laser source to render an image on an electrically-charged surface.In the past, PWM techniques have been used to improve the rendering of text/graphics in saturated primary tones, however, rendering gray or arbitrary colors using these techniques typically leads to noisy text/graphics boundaries, primarily due to the inability of a laser printer to print weak or isolated pulses at the boundaries.In this paper, rendering of all graphics/text tones is achieved by using a fast chain-code lookup table to determine the antialiasing required at a given pixel location. This table is precomputed using a wavelet-based boundary denoising algorithm. We present two techniques that use the antialiasing information to modify the output of the screening algorithm in order to generate pulse patterns that improve the stability of rendering at text/graphics boundaries. The presented techniques lead to superior text/graphics quality and smooth boundaries.
Jincheng Huang, Onur Guleryuz, Anoop K. Bhattacharjya, Joseph Shu, "Pulse-Width Modulation for Rendering Color Text and Graphics for Laser Printers" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 803 - 806, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00096_2