Method and apparatus for generating size and orientation invariant shape features
US4989257A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 30, 1989 |
| Grant date | Jan 29, 1991 |
| Priority date | — |
| Expiry date | Jan 30, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06V30/10
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A system extracts a set of size invariant, rotation invariant features from pixel data of a character and sends the set of features to a statistical decision tree to effectuate automatic recognition of a character. The set of extracted features includes a group of features that is extracted by dividing a circle bounding the character into eight rings and 24 slices and counting the number of character pixels contained in each ring and in each slice. Various Fourier transforms, autocorrelations, moment calculations, and sorting operations are performed on many of the aforementioned arrays to yield further size and orientation invariant features. The distance between the centroid of the largest hole of the character and the center of the character is computed. The ratios of the perimeters of first and second holes of the character to the outer perimeter are computed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.