Saturable smoothing grid for image processing
US5294989A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 17, 1991 |
| Grant date | Mar 15, 1994 |
| Priority date | — |
| Expiry date | Sep 17, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/21
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An image processing technique in which illumination effects are reduced by subtraction of spatially weighted masks which are formed substantially simultaneously on an analog smoothing grid. Haloing are reduced by using a mask whose spatial weighting is non-linear at the boundary of image segments whose intensities differ by more than would be predicted by the Rule of Twenty which predicts that the ratio of naturally found reflectances seldom exceeds a factor of twenty. A color image is processed by forming differently scaled masks, each of which is related to a spectral component of the original image. The masks are subtracted from the image to form a composite image. The saturation level in each smoothing grid is selected to minimize adverse effects of illumination in that spectral component by causing segmentation of image areas whose intensity differences exceed natural reflectance ratios. The transfer functions of each grid may also separately adjusted to enhance the composite image.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.