Color Conversion Table Creating Device Nonlinear Interpolation
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Solution Overview
Problem
Existing color conversion methods using linear interpolation often result in irregularities in gradation expression due to nonlinear relationships between color changes and ink quantities, leading to inconsistent tone representation when converting between RGB and CMYK color spaces.
Innovation Solution
A color conversion table creating device and method that utilizes gray, light, and dark area data to determine correspondence relationships for grid points, employing auxiliary lines and interpolation coefficients to accurately reflect nonlinear ink quantity changes, ensuring superior tone expression by interpolating between defined points in the color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If linear interpolation is used to find correlations at grid points within the color gamut, then the color conversion process is simple and fast, but irregularities in gradation expression occur due to nonlinear relationships between color changes and ink quantities
Solution Approach 1:
The color gamut is divided into multiple primary color gamuts, each corresponding to a different primary color (C, M, Y). Within each primary color gamut, the correlation between RGB and CMYK values is determined separately using gray data, light area data, and dark area data. This segmentation allows the nonlinear characteristics of different color regions to be handled independently, improving gradation accuracy while maintaining computational efficiency.
Solution Approach 2:
Different interpolation methods and data types are applied to different regions within the color gamut. Gray data is used for points on the gray line (achromatic colors), light area data for points near white, and dark area data for points near black. This local quality approach ensures that each region's specific nonlinear characteristics are accurately represented, resolving the gradation irregularities that would occur with uniform linear interpolation.
2Manufacturing precision
If the color conversion table uses detailed grid points throughout the color gamut, then tone expression accuracy is improved, but the complexity of creating and storing the conversion table increases
Solution Approach 1:
The color gamut is segmented into multiple primary color gamuts, each handling a specific primary color's contribution. This segmentation allows the conversion table to be built systematically by combining results from simpler sub-gamuts, reducing overall complexity while maintaining comprehensive tone coverage.
Solution Approach 2:
The invention changes the approach from using a single uniform interpolation method across all grid points to using multiple data types (gray data, light area data, dark area data) with different characteristics. This parameter change allows accurate representation of nonlinear ink quantity relationships without requiring excessive grid points, thus reducing table complexity while improving tone accuracy.
Data Source
AI summary
A color conversion table creating device includes a gray data creating unit, light and dark area data creating unit, first grid point correspondence relationship determining unit, second grid point correspondence relationship determining unit including gray-dark auxiliary line setting unit, intersecting point setting and signal determining units, interpolation coefficient determining unit, and second grid point interpolation unit, and color conversion table creating unit. The device sets a gray-dark auxiliary line gray and dark intersecting points, The device determines, based on gray data and dark area data, output color signals corresponding to the gray-dark auxiliary line gray and dark intersecting points determines light interpolation coefficient reflecting characteristic of light area data, and determines a relationship for the second grid point between an input color signal and an output color signal by performing interpolation between the output color signals corresponding to the gray-dark auxiliary line gray and dark intersecting points by using the light interpolation coefficient.