Edge extraction technique
US4638369A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 4, 1984 |
| Grant date | Jan 20, 1987 |
| Priority date | — |
| Expiry date | Sep 4, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30144
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An improved edge extraction technique for use in copying a halftone original to produce a halftone copy is described. The prior art uses a two path system to rescreen a halftone, a filter path to remove the original screen and an edge extraction path to enhance the edges. The final gray scale signal, before rescreening, is the addition of the outputs of the two paths. This invention is an improved edge extraction technique for use in such a system. First, the sign and magnitude of horizontal and vertical edges is computed. Then a root mean square of these values is taken to provide a two dimensional enhancement. Next, the enhancement is tested against certain thresholds to test whether the value is a result of image noise, or whether there is a probability that a small enhancement may be in the wrong direction. Finally, the enhancement is added to the filter path output.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.