Color Conversion Table Creation Using Gamut Polyhedron Extraction
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Solution Overview
Problem
Existing methods for creating color conversion tables are complex and may produce unsuitable tables due to insufficient Lab value sets, leading to increased memory requirements and calculation time when trying to determine if reference points are within the color gamut of a device.
Innovation Solution
A conversion table creating device that sets uniformly distributed reference points in both color spaces, calculates color differences, and registers corresponding data points to create a suitable color conversion table without excessively increasing the number of interpolation points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate process is performed to determine whether point P exists in the color gamut of the printer, then the accuracy of color conversion is improved, but the device complexity and calculation time increase
Solution Approach 1:
The patent applies preliminary action by pre-generating a polyhedron that represents the color gamut of the printer before the actual color conversion process. This polyhedron is created from measured Lab value sets of 729 colors and stored as reference data. During color conversion, the system only needs to check whether point P lies within this pre-generated polyhedron, rather than performing complex gamut determination calculations in real-time. This approach maintains color conversion accuracy while significantly reducing computational complexity and processing time.
2Reliability
If the number of interpolation points is increased to resolve insufficient measured Lab value sets, then the completeness of the color conversion table is improved, but the memory requirements and calculation time increase
Solution Approach 1:
The patent performs preliminary interpolation to generate a polyhedron representing the color gamut from the measured Lab value sets before creating the final color conversion table. By pre-processing the data to establish the gamut boundaries, the system can efficiently determine which reference points fall within the color gamut without needing to excessively increase the number of interpolation points in the final table. This reduces memory requirements while maintaining table completeness.
Solution Approach 2:
The patent extracts only the necessary Lab value sets that fall within the color gamut of the printer by checking whether point P lies within the pre-generated polyhedron. Instead of storing and processing all possible interpolation points, the system selectively extracts and stores only those data points that are relevant to the actual color gamut, thereby reducing memory requirements while maintaining the completeness of the color conversion table for usable colors.
3Adaptability or versatility
If reference points outside the color gamut are included in the color conversion table, then the coverage of the color space is improved, but the suitability and accuracy of the conversion table deteriorates
Solution Approach 1:
The patent extracts and identifies only those reference points that lie within the color gamut of the printer by checking whether point P is contained within the pre-generated polyhedron. The system selectively includes only these valid points in the color conversion table, excluding points outside the gamut. This ensures that the conversion table maintains high suitability and accuracy for actual printer colors while still providing comprehensive coverage of the usable color space.
Data Source
AI summary
A color data setting unit that sets a plurality of sets of fifth color data that are defined in a first color space in one to one correspondence with a plurality of fourth color data sets. An identifying unit identifies some of first reference points, that are in proximity to the fifth color data set for each of second reference points. A calculation unit calculates, for each of all the second reference points, color differences between the fifth color data set for the each second reference point and the some of the first reference points. A determining unit determines, for each of the first reference points, a single fifth color data set that has the smallest color difference among all the color differences that are calculated with respect to the each of the first reference points. A registering unit registers, at each of the first reference points, the fourth color data set that is set in correspondence with the single fifth color data sets.