Color Transform Excess Relation Gamut Control
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Solution Overview
Problem
Existing methods for creating color transforms in color imaging devices face challenges in controlling the volume and shape of the gamut when a total area coverage (TAC) limit is imposed, leading to a concave gamut shape that affects gamut mapping algorithms and limits the availability of colors.
Innovation Solution
A method that establishes an excess relation between color channel values and excess values, allowing for the inclusion of color points in the gamut only if the sum of excess values is below a predetermined limit, influencing the gamut's shape and volume, and enabling continuous mapping of out-of-gamut colors by using a gamut mapping algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a total area coverage (TAC) limit is imposed to control colorant usage, then ink usage is reduced, but the gamut shape becomes concave and color availability is limited
Solution Approach 1:
The patent transforms the conventional TAC limit approach by introducing an excess relation that maps color channel values to excess values. This parameter transformation allows the system to control total colorant usage while maintaining a convex gamut shape, resolving the contradiction between ink reduction and gamut shape preservation. The excess relation effectively changes the parameter space in which gamut constraints are applied.
2Loss of substance
If a TAC limit is imposed to reduce colorant amount, then ink usage is controlled, but gamut mapping algorithms are affected and color availability decreases
Solution Approach 1:
By introducing the excess relation that transforms color channel values into excess values, the patent enables the system to enforce colorant limits while preserving color availability. The excess relation acts as a parameter transformation layer that decouples the physical constraint (TAC limit) from the colorimetric space, allowing gamut mapping algorithms to operate effectively.
3Loss of substance
If conventional TAC limiting is applied, then ink usage is reduced, but the gamut volume is decreased
Solution Approach 1:
The patent applies parameter transformation through the excess relation to reshape the constraint boundary in color space. Instead of creating a concave gamut volume reduction, the excess relation maintains a convex gamut shape that preserves maximum volume while still enforcing the total colorant usage limit. This resolves the contradiction between ink reduction and gamut volume preservation.
Data Source
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AI summary
A method for making a colour transform for an output device is provided. The colour transform represents a correspondence relation between a first and a second colour space. Each of the two colour spaces involves a number of colour channels and the colour channels of the second colour space control the colorants in the output device. An excess relation for the colour channels of the colour space associated with the output device is established and only colour points in the second colour space wherefor a sum of the excess values related to the colour point is lower than a predetermined limit, are included in the colour transform. This enables to adapt the shape of a colour gamut to a behaviour of the colorants and enhances the flexibility in making a colour transform for various print processes.