Image processing method using a collapsed Walsh-Hadamard transform
US4549212A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 11, 1983 |
| Grant date | Oct 22, 1985 |
| Priority date | — |
| Expiry date | Aug 11, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T5/10
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An improved image processing method uses a modified Walsh-Hadamard transform to remove noise and preserve image structure in a sampled image. Image signals representative of the light value of elements of the image are grouped into signal arrays corresponding to blocks of image elements. These signals are mapped into larger signal arrays such that one or more image signals appear two or more times in each larger array. The larger arrays are transformed by Walsh-Hadamard combinations characteristic of the larger array into sets of coefficient signals. Noise is reduced by modifying--i.e., coring or clipping--and inverting selected coefficient signals so as to recover processed signals--less noise--representative of each smaller signal array. The results exhibit acceptable rendition of low contrast detail while at the same time reducing certain processing artifacts characteristic of the unimproved Walsh-Hadamard block transform.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.