Conversion of an image represented by a field of pixels in a gray scale to a field of pixels in binary scale
US4685145A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 7, 1984 |
| Grant date | Aug 4, 1987 |
| Priority date | — |
| Expiry date | Dec 7, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06V40/1347
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A gray scale image of a fingerprint composed of a field of pixels is converted to a binary image composed of a field of pixels by a technique which takes into account the directivity of the ridge and valley structure. Three intermediate binary images are developed, one by the use of a vertical filter, one by the use of a horizontal filter and a reference image by the use of a filter which is not directionally biased. Corresponding subfields around each pixel in each of the three images are compared. If the subfield for the vertically derived image is closer to that of the reference image then is the subfield for the horizontally derived image, then the binary value for the pixel from the vertically derived image is used in the final image; and vice versa. In this fashion, a fourth a final binary image is derived from a combination of the vertically derived image and horizontally derived image which includes the best imagery from each of those two intermediate images.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.