4D LUT Color Correction via 3D Interpolation
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Solution Overview
Problem
Existing image processing techniques for electrophotographic apparatuses face challenges in accurately correcting color shades of color mixtures, particularly when using multiple destination profiles or processes that do not rely on device-independent color spaces, leading to inefficiencies and large data requirements for multi-dimensional Look Up Tables (LUTs).
Innovation Solution
An image processing apparatus and method that utilizes a 4-dimensional color space conversion by forming a 4-dimensional LUT using a 3-dimensional color space conversion table and a device-independent color space, allowing for precise color shade correction across various profiles and color converting methods with reduced data requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-dimensional LUT is used to correct the color shade of the color mixture, then the color reproduction precision is improved, but the number of data for correction increases significantly
Solution Approach 1:
The patent segments the correction process into two distinct stages: first, a 3D LUT is constructed from a relatively small set of measurement data points; second, this 3D LUT is extended to a 4D LUT through interpolation techniques. This segmentation allows the system to achieve high-precision color correction while keeping the initial measurement data requirements manageable.
Solution Approach 2:
The patent transitions from a 3-dimensional color space (CMY or RGB) to a 4-dimensional color space (CMYK) by adding the black channel dimension. This dimensionality change enables comprehensive color mixture correction while using interpolation methods to generate the additional dimensional data without requiring a proportional increase in measurement points.
2Measurement precision
If the destination profile among ICC profiles is corrected to correct the color shade of the color mixture, then the color reproduction is improved, but the correcting process has to be executed to all profiles when the user uses a plurality of destination profiles
Solution Approach 1:
The patent creates a universal 4D LUT correction table that can be applied across multiple destination profiles and color converting methods. By establishing a single correction framework based on the 4-dimensional color space, the system achieves broad applicability without requiring separate correction processes for each profile, thereby reducing redundant processing time.
3Measurement precision
If a 4-dimensional LUT is formed using the same method as 1-dimensional LUT, then the color shade correction is improved, but 1048576 data points are necessary which increases the amount of chart data significantly
Solution Approach 1:
The patent performs preliminary construction of a 3D LUT from a manageable set of measurement data before extending to 4D. This preliminary action allows the system to establish a solid correction foundation with fewer data points, and then systematically expand to the full 4-dimensional space through mathematical interpolation, avoiding the need to collect and process all 1,048,576 data points upfront.
Data Source
AI summary
An image processing apparatus allows a printer to output chart data of a plurality of kinds of color mixture expressed by a three-dimensional color space constructed by CMY; obtains colorimetry values obtained from the output chart data; forms a reference value by converting patch data of the color mixture expressed by the three-dimensional color space into a device independent color space on the basis of a first color conversion table for converting the three-dimensional color space into the device independent color space; corrects a second color conversion table by using the obtained colorimetry values, the formed reference value, and the second color conversion table for converting the device independent color space into the three-dimensional color space; and forms a color conversion table for correcting a four-dimensional color space constructed by CMYK by using the first color conversion table and the second color conversion table.