Grayscale Conversion Using Brightness-Sorted Color Allocation
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Solution Overview
Problem
Existing color-to-grayscale conversion methods, such as NTSC conversion, reduce color discrimination and cause significant changes in gray values when the color scheme changes, making it difficult to maintain consistent element recognition across pages.
Innovation Solution
An image processing apparatus that corrects gradation values by adjusting those with differences smaller than a threshold value, increasing them within the threshold range, while reducing adjacent gradation value differences to maintain discrimination and minimize gray value changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization of gray value differences is performed to improve discrimination, then discrimination between adjacent gray values is improved, but gray value differences may become smaller than before equalization in some color schemes and discrimination may be reduced
Solution Approach 1:
The patent changes the parameter of gray value allocation from equal-interval distribution to distribution based on original brightness relationships. Specifically, it calculates the sum of brightness values for each color, sorts colors by this sum, and allocates gray values in sorted order while maintaining the original brightness differences. This resolves the contradiction by preserving discrimination (improving measurement precision) while maintaining consistency across color schemes (improving reliability).
Solution Approach 2:
Instead of equalizing gray value differences as in conventional methods, the patent inverts the approach by preserving the original brightness-based differences. It sorts colors according to their brightness sums and allocates gray values in that sorted order, thereby maintaining the natural brightness hierarchy rather than forcing equal intervals. This inversion resolves the contradiction between discrimination and consistency.
2Stability of the object's composition
If the same color is used for the same element over a plurality of pages with different color schemes, then color consistency should be maintained, but the gray value of the same element may significantly change from page to page due to equalization
Solution Approach 1:
The patent changes the parameter of gray value assignment from equal-interval allocation to allocation based on cumulative brightness sums. By sorting colors according to their brightness sums and assigning gray values in that order, it ensures that the same color always receives the same gray value regardless of the color scheme, while still maintaining discrimination between different colors through the brightness-based sorting.
3Device complexity
If NTSC conversion is used for color to grayscale conversion, then the conversion process is simple, but discrimination between elements that were color-coded is reduced after conversion
Solution Approach 1:
The patent changes the conversion parameters from fixed NTSC weights (0.299R + 0.587G + 0.114B) to a sorting-based approach using cumulative brightness sums. This maintains relatively simple processing while significantly improving discrimination by preserving the brightness hierarchy of different colors, allowing color-coded elements to remain distinguishable in grayscale.
Data Source
AI summary
The disclosed technique is an image processing apparatus that corrects gradation values of monochrome data converted from color data, including correction unit configured to, in the case where there are three or more gradation values after conversion and there are a plurality of gradation value differences between adjacent gradation values arranged in order of magnitude, if there is a gradation value difference smaller than a prescribed threshold value among the plurality of gradation value differences, correct the gradation value difference smaller than the threshold value to increase in the range of the threshold value or smaller by reducing other gradation value differences adjacent to the gradation value difference smaller than the threshold value.