Conversion Matrix Determining Method for Nonlinear Color Spaces
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Solution Overview
Problem
The sRGB color space, commonly used for image input/output, is nonlinear, leading to heavy processing loads due to the need for nonlinear conversion processing, which is inefficient and affects color reproducibility.
Innovation Solution
A method for determining a conversion matrix that minimizes color differences by converting image signals between nonlinear and linear color spaces, taking into account specific viewing conditions and the characteristics of the imaging apparatus, to optimize color conversion processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nonlinear conversion processing is executed for sRGB color space image input/output, then color reproducibility is maintained according to monitor gamma characteristics, but processing load increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing conversion matrices for multiple gamma values (2.0, 2.2, 2.4, 2.6, 2.8) during system initialization. When image processing is needed, the appropriate pre-computed matrix is selected based on the target gamma value, eliminating the need for real-time nonlinear conversion calculations and significantly reducing processing load while maintaining color accuracy.
Solution Approach 2:
The patent changes the parameter of gamma value from a fixed monitor-specific value to multiple selectable values (2.0, 2.2, 2.4, 2.6, 2.8). By preparing conversion matrices for different gamma parameters in advance, the system can adapt to various display devices without performing complex nonlinear conversions during actual image processing, thus resolving the contradiction between color fidelity and processing speed.
2Productivity
If conversion matrix is determined without considering viewing conditions, then processing is simpler, but color accuracy under different viewing conditions deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating conversion matrices for multiple gamma values corresponding to different viewing conditions during system initialization. These pre-computed matrices incorporate chromatic adaptation transformations that account for different illuminants (D50, D65, A, F2). When processing images, the system simply selects the appropriate pre-prepared matrix based on the target viewing condition, maintaining color accuracy without complex real-time calculations.
Solution Approach 2:
The patent changes the parameter of viewing condition from a single fixed condition to multiple configurable conditions (different gamma values and illuminants). By preparing conversion matrices for various viewing condition parameters in advance, the system enables flexible adaptation to different display environments while keeping the actual processing simple matrix multiplication operations.
Data Source
AI summary
A conversion matrix determining method for determining a conversion matrix to be used in color conversion processing executed on a photographic image, includes: obtaining image data of an image captured under a given condition and a colorimetric value measured under a condition identical to the given condition from a subject of the image data; and determining a conversion matrix to be used to execute color conversion on an image signal in a nonlinear color space where a luminance value changes nonlinearly, based upon the image data and the colorimetric value having been obtained.