Apparatus for thresholding an image signal
US4918543A · kind A · utility
14Cited by
30References
10Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Jan 24, 1989 |
| Grant date | Apr 17, 1990 |
| Priority date | — |
| Expiry date | Jan 24, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/4051
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
This invention relates to an apparatus for converting a grayscale image to a bitonal image which provides improved tonal rendition with minimal loss of resolution. The invention attenuates the low spatial frequency component of the digital image and uses a similarly attenuated thresholder to convert the image to a bitonal image. When used with a dither type thresholder, this technique allows for simultaneous "continuous tone" and "line art" thresholding with minimal circuit complexity.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.