Contrast enhancement of an image using luminance and RGB statistical metrics
US6580825B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 22, 2001 |
| Grant date | Jun 17, 2003 |
| Priority date | — |
| Expiry date | Dec 22, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/6027
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An automatic contrast enhancement method improves the quality of an image by increasing the dynamic range of the tone levels in an image without causing an undesirable hue shift. An overall stretch factor that stretches the dynamic range of all the colors is generated based on the standard deviation of the tone levels for the overall luminance of the image. A color weighting factor is used to individually control the amount that each color is stretched. The color weighting factor is based on the difference between the standard deviation of the tone levels for the overall luminance of the image and the standard deviation of the tone levels for each color. An anchor factor is used to preserve the mean tone level for each color while the tone levels far from the mean tone level are changed more dramatically than the tone levels close to the mean tone level, which minimizes hue shifts while maximizing contrast enhancement.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.