Research On Error Diffusion Algorithm In Digital Halftoning

Halftoning is one of the oldest applications of image processing, since it is essential for the printing process. Digital halftoning refers to the process of rendering continuous-tone images to binary images so that it can be printed or displayed with bi-level devices. Today, it plays a key role in almost every discipline that involves printing and displaying. All newspapers, magazines, and books are printed with digital halftoning. So the research on digital halftoning is of great significance for its wide application.In this thesis, the author mainly studies digital halftoning and error diffusion algorithm, which is hotly discussed and proves to be one of the best halftoning methods available today.First the author systematically discusses the digital halftoning theory. Not only the principle and its development are presented, but also some main methods available and key techniques. The second part focuses on error diffusion algorithm, which is the most important part of the thesis. The author analyzes the algorithm and discusses three key elements influencing halftoning process: error diffusion filter, threshold modulation and scanning path. Finally, the author builds a digital halftoning bench and presents two new error diffusion algorithms. In order to deeply understand error diffusion, the halftones with different filters and scanning paths are compared and analyzed, which lays a strong foundation for further study. One of the algorithms is named Perceived Error-Based Error Diffusion (PEB Error Diffusion), which efficiently reduces the structured artifacts in midtone area and results in higher visual quality. The other is Adaptive Error Diffusion with Perceived Error Feedback (PEF Error Diffusion), which enhances the overall contrast, gives more details, and displays better visual quality than traditional algorithm.