Color Conversion Gray Level Correction via Lookup Table
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Solution Overview
Problem
Color conversion processes often result in undesirable image quality and ink wastage due to differences in color spaces between devices, particularly when converting gray colors, leading to banding and artifacts.
Innovation Solution
The method involves identifying non-pure gray color values, converting them to corresponding pure gray values, determining difference vectors, and applying correction factors to selected color values to produce corrected color values, while preserving the pure gray nature of colors during conversion between color spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional color space conversion is used, then conversion speed is improved, but gray color integrity deteriorates causing banding and artifacts
Solution Approach 1:
The patent introduces an intermediary processing step between conventional color space conversion and final output. A correction table is created that maps converted gray colors back to their original gray values, acting as a mediator to fix the banding and artifact problems caused by direct conversion while maintaining the speed benefits of conventional methods.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing correction values in a correction table before actual color conversion occurs. This lookup table is prepared in advance based on the relationship between source and destination color spaces, allowing fast correction during runtime without compromising conversion speed.
2Device complexity
If gray colors are converted using conventional methods, then conversion simplicity is improved, but image quality deteriorates due to banding and artifacts
Solution Approach 1:
The correction table serves as an intermediary that bridges the simple conventional conversion process and the quality requirements. It adds minimal complexity by providing a lookup-based correction step that eliminates banding and artifacts while preserving the overall simplicity of the conversion workflow.
3Manufacturing precision
If pure gray values are enforced in conversion, then gray color purity is improved, but color transition smoothness deteriorates causing visible banding
Solution Approach 1:
The patent applies local quality by making the correction selective rather than universal. The correction table specifically targets gray color values that have been affected by conversion errors, applying correction only where needed. Non-gray colors remain unaffected, preserving their natural transitions and avoiding unnecessary modifications.
Data Source
AI summary
Systems and methods, including computer software products, for processing gray colors in a conversion between color spaces involve identifying a non-pure gray color value in a color space that represents a substantially gray color. The methods further include converting the non-pure gray color value to a corresponding pure gray color value in the color space. The methods also include determining a first difference vector between the non-pure gray color value and the corresponding pure gray color value. The methods further include determining a distance between the corresponding pure gray color value and a selected color value. The corresponding pure gray color value represents a nearest pure gray color value to the selected color value. The methods also includes determining a correction factor based on the first difference vector and the distance and applying the correction factor to the selected color value to produce a corrected color value.