Apparatus and methods for locating edges and document boundaries in video scan lines
US4833722A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 1987 |
| Grant date | May 23, 1989 |
| Priority date | — |
| Expiry date | Jul 24, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/403
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus, and accompanying methods for use therein, for locating edges contained within each scan line of a scanned video image and also for locating horizontal boundaries (leading and trailing edges) of a portion of a document contained within the scan line are described herein. Specifically, this apparatus first provides a background value representative of a background level in a scanned image and associated with an incoming pixel value. If the background value exceeds a first reference value, a first signal is generated. If the incoming pixel value exceeds a second reference value, a second signal is generated. Now, an edge transition is detected based upon a pre-defined logical combination of the first and second signals. If such a transition has been detected, such as a leading or trailing edge in either the incoming pixel values or in the background level, a control circuit, illustratively implemented using a programmed array logic circuit and various counters, determines if the edge transition is associated with valid leading or trailing edge, i.e. wheter the transition itself is followed by a pre-determined number of similar pixel values. If a valid leading or trailing ed…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.