Method of and apparatus for obtaining binary image
US5315409A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 19, 1992 |
| Grant date | May 24, 1994 |
| Priority date | — |
| Expiry date | Feb 19, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30141
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A frequency distribution or histogram M (L.sub.j-1, L.sub.j) of differences between gradation levels (L.sub.j-1, L.sub.j) of adjacent pixels (P.sub.j-1, P.sub.j) in an image is obtained, and the number of level-changes for each tentative threshold level L.sub.j is determined as a function of the histogram of the level differencies. By using the number of level-changes, an optimum binarization threshold level is set by means of an adaptive thresholding method. Since the number of level-changes is calculated from the histogram of the level-differencies without practical binarization for each threshold level, the amount of calculations is not dependent on the number of pixels but on the number of gradation levels. The calculations for setting the threshold level for the binarization of the image are achieved at high speeds by a small-scale hardware.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.