Special-Color RGB-to-Lab Calibration with Segmented Data
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Solution Overview
Problem
Existing methods for calibrating printing devices using special colors other than CMYK face challenges in accurately converting RGB values to Lab values due to the complexity of five-dimensional color combinations, leading to labor-intensive and inaccurate conversions.
Innovation Solution
An information processing system and method that utilizes a memory to store conversion data for each combination of basic and special colors, allowing selection and conversion of RGB values to Lab values with high accuracy, even in cases where all combinations of Lab values are not present, by using a calibration chart with reduced dimensional color patch images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conversion data is created based on five-dimensional color patch images including special colors, then color gamut is expanded, but conversion accuracy deteriorates and labor required increases enormously
Solution Approach 1:
The patent segments the five-dimensional color space into multiple three-dimensional subspaces, each corresponding to a specific combination of basic colors and special colors. By dividing the complex color space into manageable segments, the system achieves accurate conversion within each segment without requiring exhaustive measurement of all possible five-dimensional combinations.
Solution Approach 2:
The patent applies local quality by creating conversion data with high accuracy for specific local regions (three-dimensional color combinations) rather than attempting uniform coverage of the entire five-dimensional space. Each local conversion dataset is optimized for its specific color combination, ensuring high conversion accuracy where needed while reducing overall complexity.
2Reliability
If all combinations of five-dimensional color patch images are measured, then complete conversion data is obtained, but the number of patch images becomes enormous and labor required is unrealistic
Solution Approach 1:
The patent divides the complete set of five-dimensional color combinations into multiple three-dimensional segments based on which special colors are present. This segmentation reduces the measurement burden from measuring all possible five-dimensional combinations to measuring only the necessary three-dimensional subsets, dramatically improving calibration efficiency while maintaining conversion completeness.
Solution Approach 2:
The patent applies partial action by measuring only the necessary three-dimensional color combinations rather than all possible five-dimensional combinations. This partial measurement approach is sufficient to achieve accurate conversion for the intended application while avoiding the excessive labor of complete five-dimensional coverage.
3Device complexity
If five-dimensional color values are converted directly to three-dimensional RGB values, then conversion is simplified, but accuracy is lost due to information compression
Solution Approach 1:
The patent segments the five-dimensional to three-dimensional conversion process into multiple three-dimensional conversion steps, each handling a specific color combination. This segmentation allows each conversion step to maintain high accuracy by working within a well-defined three-dimensional color space rather than attempting a single complex five-dimensional to three-dimensional mapping.
Data Source
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AI summary
An information processing system includes a memory that stores plural pieces of conversion data for converting RGB values into Lab values, for each combination of plural colors, the plural pieces of conversion data being generated by using a calibration chart including multi-dimensional color patch images consisting of combinations of plural basic colors and multi-dimensional color patch images consisting of combinations of plural colors obtained by replacing any one color of the plural basic colors with a special color other than the basic colors, and a processor configured to select, with respect to RGB values in a case where a patch image in the calibration chart is read by an image reading device, conversion data corresponding to the patch image from among the plural pieces of conversion data stored in the memory, in accordance with combination information indicating which of combination of the plural colors the patch image corresponds to, convert the read RGB values into Lab values by using the selected conversion data, and generate a multi-dimensional LUT for executing calibration by using the converted Lab values.