Multiple spatial channel printing
US5920653A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 22, 1996 |
| Grant date | Jul 6, 1999 |
| Priority date | — |
| Expiry date | Oct 22, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/4057
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A multiple spatial channel technique is described that can produce near continuous-tone output quality from an output device having a large, dilute dot channel, referred to as the L (lowpass) channel, and a small, concentrated dot channel, referred to as the N (noisy) channel. The new process described here overcomes contouring artifacts and produces vastly improved images over techniques that use only a single dot type. Given a matrix of image luminance values (raster), two images are computed for printing with the two channels of the printer. The two images are computed simultaneously with a two-pass algorithm, one pass horizontally and one pass vertically. Initially, the L channel image is set to be equal to the input image. Each adjacent pair of pixels in the original image is compared by calculating an edge contrast strength. If the ratio of the first pixel level to the second pixel level is larger than a threshold, the L channel pixel that corresponds to the second image pixel is set to the first pixel level. On the other hand, if the ratio of the second pixel level to the first pixel level is larger than the threshold, the L channel pixel that corresponds to the first image …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.