Method and apparatus for image descreening
US6222641A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 1, 1998 |
| Grant date | Apr 24, 2001 |
| Priority date | — |
| Expiry date | Jul 1, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/40075
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An image descreening process first smoothes the image, where smoothing is accomplished by applying a convolution with a low pass filter (LPF) kernel, which is a parameter to the descreening function. Using the smoothed image, a determination is made for each pixel for which pixels around it participate in the modified filter. For a current pixel, a window is considered having the size of the LPF kernel, with the current pixel at the center. A threshold T1 which is given as a parameter, is used to mark the pixels in the current window. Considering a pixel in the window, if for all color components the difference between this pixel value to the center pixel value is less than T1 in absolute value the pixel is marked with a 1. Otherwise, the pixel is marked with a 0. Finally, an adaptive version of the LPF is applied. If the number of pixels marked with a 1 in the window is less than a third of the kernel size, the original pixel value is restored. Additionally, for a color component for which there is a small change in values within the original (non-smoothed) window (i.e. the difference between the maximal value to the minimal value in this component is less than another threshold T…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.