Color Processing Apparatus Quadrant-Based Tetrahedron Segmentation
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Solution Overview
Problem
Existing color conversion methods using tetrahedron interpolation in color management systems often result in unintended interpolation results and tone distortion, particularly in regions not in contact with the gray axis, due to uniform segmentation across the entire color space.
Innovation Solution
Adopting a segmentation method that varies depending on the quadrant to which the input signal value belongs, allowing for different division directions for unit cubes in the L*a*b* space, thereby ensuring bilaterally symmetrical interpolation results and preventing tone distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same segmentation method is used across the entire L*a*b* space to divide unit cubes into tetrahedrons, then the interpolation operation is simple and computationally efficient, but unintended interpolation results and tone distortion occur in regions not in contact with the gray axis
Solution Approach 1:
The patent applies different segmentation methods to different regions (quadrants) of the L*a*b* color space. Specifically, for quadrants where a*≥0 and b*≥0, or a*<0 and b*<0, one segmentation method is used, while for quadrants where a*≥0 and b*<0, or a*<0 and b*≥0, a different segmentation method is applied. This local differentiation ensures accurate interpolation results in each region while maintaining overall computational efficiency.
2Ease of operation
If uniform segmentation is applied across all quadrants of the L*a*b* space, then the color conversion process is simple and fast, but color continuity and tone representation are distorted, particularly away from the gray axis
Solution Approach 1:
The patent introduces asymmetry in the segmentation approach by recognizing that different quadrants of the L*a*b* space have different geometric relationships with the gray axis. By applying symmetric segmentation only where appropriate (quadrants containing the gray axis) and asymmetric segmentation in other regions, the patent achieves both computational simplicity and color continuity accuracy.
3Manufacturing precision
If a 3DLUT with fine grid spacing is used to improve interpolation accuracy, then tone distortion is reduced, but the memory requirements and processing complexity increase significantly
Solution Approach 1:
The patent segments the L*a*b* color space into different quadrants and further divides each unit cube into tetrahedrons with specific vertex selections based on the quadrant. This segmentation strategy allows the use of a relatively coarse 3DLUT grid while achieving accurate interpolation results by carefully selecting which vertices to use for interpolation in each region, thereby reducing both memory requirements and processing complexity compared to using a uniformly fine grid throughout.
Data Source
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AI summary
When performing color conversion using a color conversion table which has signal values of an output color space corresponding to grid points dividing an input color space into a plurality of unit cubes, a quadrant to which an input signal belongs is determined, in a chromaticity plane perpendicular to a lightness axis of the input color space. A unit cube to which the input signal belongs is detected in the plurality of unit cubes. The detected unit cube is divided into a plurality of polyhedrons for interpolation operation by a segmentation method corresponding to the determined quadrant. The divide of the detected unit cube is performed along a direction of a diagonal line, which passes through an origin of the chromaticity plane, in a part of the plurality of unit cubes in accordance with the segmentation method.