Encoded orphan pixels for discriminating halftone data from text and line art data
US5987221A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 24, 1997 |
| Grant date | Nov 16, 1999 |
| Priority date | — |
| Expiry date | Jan 24, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40062
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Text and line art image data is distinguished from halftone image data for selectively enhanced rendering thereof. Specifically, a method of rendering a raster pixel image from a stored bitmap includes (i) determining whether an orphan pixel is detected within a bounded sampling window of the bitmap, and, (ii) processing at least one selected pixel of the bitmap within the sampling window relative to the determining of whether an orphan pixel is detected. In general, an orphan pixel is defined as an isolated white or black pixel in a halftone image. In one embodiment, an orphan pixel is recognized as having a predefined pixel value and as having no other pixels with that value adjacent thereto within the sampling window. In the event an orphan pixel is detected within the window, then the bitmap within the window is determined to be halftone image data and the selected pixel is processed accordingly. In the event an orphan pixel does not exist within the window, then the bitmap within the window is recognized as text or line art image data and processed respectively. In addition, a method of forming a dither matrix for a halftone image includes generating a pixel pattern such that …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.