Imposed weight matrix error diffusion halftoning of image data
US5313287A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 30, 1993 |
| Grant date | May 17, 1994 |
| Priority date | — |
| Expiry date | Apr 30, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G3/2059
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Methods are disclosed for improving output image quality and reducing processing time in digital halftoning systems. The direction of processing each scan line of a source image is selected with blue noise, rather than the tradional raster scan sequence, to reduce directional and start-up anomalies. Source image pixel gray values are adjusted by means of imposed matrices, prior to error diffusion, in order to minimize distracting patterns and other anomalies in the output image. Error diffusion threshold values are modulated with blue noise, and the average threshold value reduced to reduce start-up delay. Finally, error terms in the error diffusion process are diffused according to a new three-weight filter. The three-weight filter substantially reduces error diffusion processing time, without sacrificing output image quality when used in combination with the modulated error diffusion threshold values.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.