Color Profile Lookup Table Black Channel Mapping
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Solution Overview
Problem
Existing color-management systems fail to achieve idealized black conversion of CMYK colors when converting between color spaces, leading to inaccurate representations and sudden transitions, particularly when dealing with gradients or images.
Innovation Solution
A system that updates color profiles by identifying the darkest output color value in the destination color space and mapping source colors with maximum black channel values to their achromatic equivalent, ensuring smooth transitions and accurate black representation, while maintaining the flexibility of the ICC framework.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If black-point compensation is used to map darkest CMYK to darkest RGB, then black conversion is improved, but flexibility of ICC framework is lost
Solution Approach 1:
The patent segments the black conversion problem by treating maximum black channel values (K=100%) as a distinct case from other CMYK colors. It identifies and separates the lookup table entries corresponding to maximum black values, allowing them to be mapped to the darkest output color value independently, while leaving other color conversions unchanged. This segmentation enables precise black conversion without requiring a specially constructed CMYK profile.
Solution Approach 2:
The patent performs preliminary identification of the darkest output color value in the destination color space before executing the color conversion. By pre-determining this reference value and storing it in a variable, the system prepares the necessary mapping target in advance, enabling efficient and accurate black conversion during the actual color profile application without requiring special profile construction.
2Measurement precision
If device link profiles are used for direct CMYK to RGB mapping, then idealized black conversion is achieved, but profile availability and software compatibility are reduced
Solution Approach 1:
The patent makes the black conversion improvement universal by implementing it as a general modification to the color profile application process rather than requiring a specialized device link profile. The method works with any existing CMYK to RGB color profile by simply updating the lookup table entries for maximum black values, making it compatible with standard ICC frameworks and widely available software without requiring specialized profile creation tools.
Solution Approach 2:
The patent creates a modified version of existing color profiles by copying the original lookup table and updating only the specific entries corresponding to maximum black channel values. This approach allows the use of standard, commonly available color profiles while achieving idealized black conversion, avoiding the need for specialized device link profiles that are not commonly available or supported.
3Productivity
If simple mathematical relationships are used for CMYK to RGB conversion, then computational speed is improved, but color representation accuracy deteriorates
Solution Approach 1:
The patent uses the lookup table in the color profile as an intermediary structure that pre-computes accurate color mappings. By storing pre-calculated RGB values for various CMYK combinations in the lookup table, the system achieves both accuracy (through pre-computed values) and speed (through direct table lookup rather than complex real-time calculations). The modification to map maximum black values to the darkest output color value maintains this efficiency while improving black conversion accuracy.
Data Source
AI summary
A system that converts color coefficients between color spaces. During operation, the system receives a color profile comprising a lookup table which defines a conversion of color coefficients between a source color space and a destination color space, wherein the source color space includes a black color channel. Next, the system identifies a darkest output color value in the destination color space produced by the color profile, and also identifies entries in the lookup table corresponding to a maximum possible value for the black color channel of the source color space. The system then updates the identified entries with an achromatic equivalent of the identified darkest output color value, whereby source colors having the maximum possible value for the black color channel are mapped to the achromatic equivalent of the identified darkest output color value.