Color Processing Apparatus Using B-Spline Solid Interpolation
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Solution Overview
Problem
Current color processing methods, such as tetrahedral interpolation and gamut mapping, often result in image disturbances like pseudo edges and decreased precision due to abrupt changes in color reproduction, especially when grid intervals are coarse or near gamut boundaries, making it difficult to achieve smooth color adjustments and high gray balance.
Innovation Solution
The use of multiple summation calculations with piecewise polynomials as basis functions allows for smooth color changes and precise prediction of color signal values, enabling direct color designation and correction within a local region, thereby reducing oscillations and improving gray balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If tetrahedral interpolation is used for color calculation, then calculation speed is improved, but image disturbance occurs due to switching of linear interpolations
Solution Approach 1:
The patent pre-divides the color space into tetrahedral regions and pre-calculates interpolation coefficients before actual color conversion is needed. By preparing the geometric structure and calculation parameters in advance, the system achieves fast real-time color conversion while maintaining smooth transitions across tetrahedron boundaries, eliminating image disturbances caused by runtime interpolation switching.
2Quantity of substance
If coarse grid intervals are used in LUT, then memory usage is reduced, but image disturbance occurs due to abrupt value changes
Solution Approach 1:
The patent applies curved transition surfaces (quadric surfaces) instead of flat tetrahedral planes to model color value transitions. These curved surfaces smoothly connect coarse grid points in the LUT, eliminating abrupt value changes at boundaries while maintaining memory efficiency. The quadratic interpolation along scan lines provides continuous second-order derivatives, ensuring smooth gradation transitions even with sparse LUT data.
3Manufacturing precision
If gamut mapping is used for color correction, then color reproduction is improved, but direct color designation becomes difficult
Solution Approach 1:
The patent implements local color correction by allowing users to specify correction parameters at particular color points or regions within the color space. The system then applies targeted adjustments using quadratic interpolation that affects only local areas, preserving the ability to directly designate and control specific colors while maintaining improved color reproduction through gamut mapping techniques.
4Measurement precision
If tetrahedral interpolation is used for color correction, then correction precision is improved, but oscillation occurs in color values
Solution Approach 1:
The patent replaces linear tetrahedral interpolation with quadratic interpolation along curved surfaces. This higher-order interpolation method provides smoother color value transitions by continuously varying the interpolation weights according to quadratic functions, eliminating the oscillations and artifacts that occur with linear methods while maintaining or improving correction precision through better modeling of actual color transitions.
Data Source
AI summary
When tetrahedral interpolation is used in correction of color reproduction upon color adjustment, image disturbances such as pseudo edges and the like may occur since the surfaces of each tetrahedron satisfy the boundary condition. Hence, a pixel position of digital image data is calculated, RGB values at that pixel position are acquired, and the acquired RGB values are displayed on RGB value display area. L*a*b* values are calculated based on basis functions and coefficient values of a color calculation B-spline solid, and the calculated L*a*b* values are displayed on an L*a*b* value display area.