Color Gamut Mapping via Curvature-Aware Lightness Functions
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Solution Overview
Problem
Existing color gamut mapping methods fail to accurately account for the non-linear curvature of color spaces, leading to mismatches in color mapping, especially when mapping source colors to target colors outside their respective constant-hue leaves, resulting in inappropriate lightness information and geometrical mismatches.
Innovation Solution
A method of color gamut mapping that uses lightness mapping functions defined to account for source and target cusp colors across multiple constant-hue leaves, incorporating average lightness values and hue intervals representative of the color space curvature, ensuring accurate lightness mapping by considering multiple cusp colors with varying hues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lightness mapping is performed using only the cusp color of the same constant-hue leaf, then the mapping is simple and computationally efficient, but the accuracy deteriorates due to non-linear curvature of color spaces causing geometrical mismatches
Solution Approach 1:
The invention segments the color space into multiple constant-hue leaves and selects cusp colors from different leaves (not just the same leaf) to define the lightness mapping function. This segmentation approach allows the method to account for non-linear curvature across the entire color gamut while maintaining computational efficiency by working within discrete hue intervals.
Solution Approach 2:
The invention extends the lightness mapping from a 2D problem (within a single constant-hue leaf) to a 3D problem by incorporating cusp colors from multiple constant-hue leaves with different hues. This dimensional extension allows the mapping to capture the non-linear curvature of the color space boundaries more accurately.
2Measurement precision
If lightness mapping uses cusp colors from multiple constant-hue leaves, then color mapping accuracy improves by accounting for non-linear curvature, but device complexity increases
Solution Approach 1:
The invention applies local quality by defining the lightness mapping function locally within each constant-hue leaf using only the cusp colors from relevant leaves. Each leaf's mapping is optimized independently based on its specific geometric relationship with neighboring leaves, rather than applying a single global mapping function. This reduces overall complexity while maintaining accuracy.
Solution Approach 2:
By segmenting the color space into constant-hue leaves and processing each segment independently with its own lightness mapping function, the invention reduces the complexity of any single mapping function while collectively achieving high overall accuracy. The segmentation allows complex non-linear relationships to be handled in smaller, more manageable pieces.
3Device complexity
If existing color gamut mapping methods are used, then the process is simple, but geometrical mismatches occur on gamut boundaries and cusp lines due to ignoring non-linear curvature
Solution Approach 1:
The invention explicitly accounts for the non-linear curvature of color spaces by using cusp colors from multiple constant-hue leaves to define the lightness mapping function. This curvature-aware approach ensures that gamut boundaries and cusp lines are mapped accurately, preserving the geometric integrity of color regions while adapting to the non-linear structure of color spaces.
Data Source
AI summary
For the mapping in a non-linear color space of source colors belonging to a same constant-hue leaf, instead of using a lightness mapping function based only on a cusp lightness condition stating that a source cusp color of this leaf should be mapped into a corresponding target cusp color of this leaf, it is proposed to build such a function also on other source cusp color(s) and other target cusp color(s) having hues different from that of said leaf. Preferably, the hue interval in which these other colors are considered is representative of the curvature of the non-linear color space at the position of colors of this constant-hue leaf.