Gamut Mapping Angle Adjustment for Color Reproduction Accuracy
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Solution Overview
Problem
Existing color-image output devices face challenges in maintaining color-reproduction accuracy and gradation characteristics, especially in low-lightness regions, when using a reduced quantity of color material and when the gamut of the second device is narrower than the first device, leading to deteriorated color-reproducing accuracy and gradation.
Innovation Solution
A color-adjusting method that maps out-gamut colors within the gamut of the second device by dividing the region outside the gamut into high-lightness, low-chroma, and medium-high-chroma regions, using a processor to adjust lightness and chroma values based on a defined gamut-mapping angle, and optimizing the gamut-mapping process to reduce the absolute value of the gamut-mapping angle in the high-chroma region, thereby enhancing color-reproduction accuracy in low-lightness areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the quantity of color material is reduced to prevent showing through on thin paper, then resource consumption is saved, but color-reproduction accuracy in low-lightness area is deteriorated
Solution Approach 1:
The color space is segmented into multiple regions based on lightness and chroma values. The low-lightness region is further divided into a first region (lower chroma) and a second region (higher chroma). Different gamut-mapping angles are applied to each region, allowing optimized color material usage while maintaining color-reproduction accuracy in critical areas.
Solution Approach 2:
Different gamut-mapping angles are applied to different regions of the color space. Specifically, a first gamut-mapping angle is used for the first region and a second gamut-mapping angle is used for the second region. This local differentiation ensures that color-reproduction accuracy is maintained where needed while reducing color material consumption overall.
2Adaptability or versatility
If gamut mapping is performed to convert out-gamut colors within the gamut, then color compatibility is improved, but color-reproduction accuracy and gradation characteristics are deteriorated
Solution Approach 1:
The gamut-mapping angle is made dynamic rather than fixed. The angle varies depending on the region in which the color lies. For colors in the low-lightness region with lower chroma, one angle is used, while for colors with higher chroma, a different angle is used. This dynamic adjustment maintains color-reproduction accuracy while achieving gamut compatibility.
Solution Approach 2:
The parameters used for gamut mapping (lightness and chroma values) are adjusted based on the specific region. By changing the gamut-mapping angle parameter according to the region, the system achieves both gamut compatibility and color-reproduction accuracy.
Data Source
AI summary
Provided are a color-adjusting method and a non-transitory computer readable medium storing a color-adjusting program. The color-adjusting method is used in converting colors of a first device into colors of a second device. The method includes: using a processor of a color-conversion device to perform: representing the gamut of the second device on a lightness-chroma plane for a hue in a color system; obtaining a limiting value of a total quantity of color material; dividing a region outside the gamut into a high-lightness region and a low-lightness region, and further dividing the low-lightness region into a low-chroma region and a medium-high-chroma region based on a reference point defined according to the limiting value; defining a gamut-mapping angle for each of the resulting divided regions; and mapping out-gamut colors within the gamut of the second device by using the gamut-mapping angle.