Scanner Profile Creation Using K Value Mediation for Color Accuracy
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Solution Overview
Problem
Existing methods for color calibration in production print struggle with achieving high precision, particularly in converting device-dependent RGB values to device-independent color spaces like CIE XYZ, due to issues such as scanner metamerism and differences in K plate amounts leading to inaccurate color measurements.
Innovation Solution
A method involving a scanner and a colorimeter to read and measure chart images with varying C, M, Y, K values, creating a scanner profile that maps RGB values from the scanner to CIE XYZ values, incorporating K values to account for differences in colorimetric values, thereby enhancing color conversion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a look-up table is optimized based on colorimetric values for color charts, then color conversion accuracy is improved, but scanner metamerism causes different RGB data values for the same colorimetric values
Solution Approach 1:
The patent segments the color conversion process by creating separate look-up tables for different manuscript classes (printed manuscript, silver halide photography manuscript, etc.). Instead of using a single unified look-up table, the system divides the color space into multiple segments, each with its own optimized conversion parameters, thereby addressing scanner metamerism that affects different manuscript types differently.
Solution Approach 2:
The patent changes the parameters of the look-up table based on the type of manuscript being scanned. By adjusting the conversion parameters specific to each manuscript class (printed manuscript, silver halide photography manuscript, etc.), the system achieves accurate color conversion for each category while accounting for the scanner metamerism characteristics of that specific type.
2Device complexity
If same-color patches are formed with different K plate amounts, then the scanner reads them as the same RGB data, but the colorimetric values from the colorimeter are not necessarily the same
Solution Approach 1:
The patent introduces an intermediary correction process that uses the known K plate amount information as a mediator to adjust the color conversion. When the scanner reads patches with different K plate amounts, the system uses the K value as an intermediate parameter to apply appropriate corrections, ensuring that the final colorimetric values accurately reflect the intended colors despite the scanner's tendency to read them as the same RGB data.
3Measurement precision
If color calibration is conducted using traditional methods, then color accuracy is improved, but the calibration process requires high-level knowledge and takes significant time
Solution Approach 1:
The patent implements a self-service calibration system that automatically performs color calibration without requiring user intervention or high-level knowledge. The system automatically scans color charts, analyzes the RGB data, generates appropriate look-up tables for the detected manuscript class, and applies corrections. This automation eliminates the need for manual calibration procedures while maintaining high color accuracy.
Solution Approach 2:
The patent performs preliminary classification of the manuscript type before conducting color calibration. By first identifying whether the document is a printed manuscript, silver halide photography manuscript, or other type, the system can pre-load the appropriate look-up table and conversion parameters, streamlining the calibration process and eliminating the need for users to manually select calibration settings.
Data Source
AI summary
A method for creating a scanner profile according to the present invention includes the steps of: by reading, by a scanner, a printed material of chart image data comprising a plurality of patches which are composed of C, M, Y, K values and differentiated in color and density from each other, acquiring a first color value for the patches; acquiring a K value for the patches of the chart image data; acquiring a second color value for the patches by color-measuring the printed material by the colorimeter; and creating a scanner profile describing a relationship of the second color value to the first color value and the K value, based on the acquired first color value, K value, and second color value for each of the plurality of patches.