Method and apparatus for generating size and orientation invariant shape features
US4802230A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 13, 1987 |
| Grant date | Jan 31, 1989 |
| Priority date | — |
| Expiry date | Mar 13, 2007 |
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 first group obtained by generating arrays representable as dimensions and other geometric qualities of six minimum bounding rectangles rotated about the character, including the distances between the center points of the rotated bounding rectangles. A second group of features is extracted by generating a group of arrays representing the perimeter pixel locations, radii lengths, and direction codes. The arrays of that group are "resampled" to generate corresponding 64 point arrays. The resampled array of direction codes is smoothed and incremental direction codes are computed and compared to preselected thresholds to obtain features that indicate prominent convex and concave portions of the character. A third group of features 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, autoco…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.