Halftone detection and delineation
US4403257A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 19, 1982 |
| Grant date | Sep 6, 1983 |
| Priority date | — |
| Expiry date | Mar 19, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40062
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In a reprographic system, a method for distinguishing halftone areas from text in an original. The system raster input scanner produces lines of binary data. A predetermined set of bits within a moveable window is inspected and the probability of that particular set of bits being taken from a halftone area of the original is assigned. The window is moved, bit by bit, and line by line, while an accumulation of probability scores is accomplished. Then, the determination, halftone or text, is made for each 32 by 32 bit block, based on a comparison of the accumulation to a predetermined threshold number. Finally, the block decisions themselves are inspected for halftone areas that may have been classified as text because of very high or low density. If surrounding blocks were determined to be halftone, the internal block will be corrected to halftone also.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.