Digital color image processing method employing histogram normalization for tone and color reproduction
US4745465A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 24, 1986 |
| Grant date | May 17, 1988 |
| Priority date | — |
| Expiry date | Mar 24, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/6027
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A digital color image processing method includes generating color reproduction functions by normalizing samples of color values from the image, and processing the color components of the color digital image by applying the color reproduction functions to the respective color components of the digital image. The samples of color values are selected from the digital image by operating on a luminance component of the digital color image with an image detail detection operator to detect regions of the image representing luminance detail, and operating on the color components of the digital image in the luminance detail regions with a contrast detection filter to detect the contrast of the color components of the image in the luminance detail regions. The color values in the luminance detail regions are separated into contrast intervals and histograms in the contrast intervals are formed. One of the contrast intervals is selected based on the similarity in shape of the color value histograms in the contrast interval. The color reproduction functions are formed by normalizing the histograms in the selected contrast interval.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.