Method and apparatus for vectorizing documents and symbol recognition
US4603431A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 14, 1983 |
| Grant date | Jul 29, 1986 |
| Priority date | — |
| Expiry date | Mar 14, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/4115
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An apparatus codes a scanned document locally representing each graphic element within a prescribed measure of accuracy by a trapezoidal approximation. The invention also includes a method for similarly coding a scanned document. The apparatus determines whether each scanned run is indicative of a Y- or .lambda.-junction, the termination of an old, or the commencement of a new graphic element, and whether a new linear approximation is necessary. The invention in a preferred embodiment recognizes symbols by determining the center of mass and maximum extremity of a symbol candidate, and comparing it to a reference library after normalizing with respect to scale, orientation and center of mass. In a preferred embodiment, an adaptive threshold parameter governs coding so as to reject noise and optimize a pair of linear predicters in a small number of scans. In a further preferred embodiment the accuracy of the linear predicters is refined so that the error is exponentially bounded.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.