Color Image Processing Apparatus for Natural Skin Tone Boundaries
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Solution Overview
Problem
Conventional color correction techniques for images, particularly those involving skin tones, often result in unnatural color transitions at boundaries between skin colors and other colors, and require separate corrections for different printing sheets, making the process cumbersome.
Innovation Solution
A method for color image processing that uses lightness, saturation, and hue correction factors to maintain natural color transitions by converting input color values into lightness, saturation, and hue values, and applying correction factors that monotonically decrease from the specified color values, allowing for independent correction of skin tones and adjacent colors, while also accommodating different printing sheets through modulation and correction factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional color correction techniques are used to correct skin color regions, then the specified color can be corrected, but the boundary between skin color and other colors becomes unnatural
Solution Approach 1:
The patent applies different correction strategies to different regions: skin color regions use lightness-based correction with lower correction strength, while non-skin regions use standard correction. This local differentiation ensures natural transitions at boundaries while maintaining correction accuracy in each region.
Solution Approach 2:
The patent changes the correction parameter from saturation/hue correction to lightness correction for skin regions, and adjusts the correction strength parameter to be lower for skin regions. This parameter transformation resolves the boundary unnaturalness problem while maintaining color correction effectiveness.
2Manufacturing precision
If saturation and hue are corrected independently for skin color, then color accuracy improves, but primary colors are also corrected and lose their primary color characteristics
Solution Approach 1:
The patent applies different correction approaches to different color regions: skin regions receive lightness-based correction with reduced strength, while primary color regions receive enhanced protection through higher correction thresholds. This local differentiation preserves primary color characteristics while maintaining skin tone accuracy.
Solution Approach 2:
The patent preemptively protects primary colors by setting higher correction thresholds and applying lightness-based correction that prevents excessive saturation/hue changes. This preliminary protection prevents primary colors from losing their characteristics before the correction process fully executes.
3Manufacturing precision
If color image information is corrected for natural colors on glossy paper, then colors display naturally on high-gamut sheets, but colors cannot be displayed naturally on standard paper with small color gamut
Solution Approach 1:
The patent creates a universal correction system that adapts to different printing sheet types through lightness-based correction. By using lightness as the primary correction parameter rather than saturation/hue, the system maintains compatibility across different color gamuts while preserving natural color appearance on various media types.
Solution Approach 2:
The patent implements dynamic correction strength adjustment based on the target printing sheet type. The correction parameters are modified according to the color gamut characteristics of the destination medium, enabling the same correction algorithm to produce natural results on both glossy and standard paper.
4Manufacturing precision
If separate color correction is performed for each type of printing sheet, then color accuracy for each sheet type improves, but the correction operation becomes troublesome and complex
Solution Approach 1:
The patent develops a universal lightness-based correction algorithm that works across all printing sheet types without requiring separate correction procedures. The system automatically adapts to different color gamuts through parameter adjustment, eliminating the need for users to perform separate corrections for each sheet type while maintaining color accuracy.
Solution Approach 2:
The patent transforms the correction approach from multiple separate correction procedures to a single unified lightness-based correction process. By changing the correction parameter from saturation/hue to lightness, the system achieves sheet-type independence, simplifying the operation while preserving color accuracy across different media.
Data Source
AI summary
An image processing apparatus for color image information inputs a combination of component values of reference colors that constitute a processing color, and converts the combination of component values into a lightness value, saturation value, and hue value. The first correction factor, the second correction factor, and the third correction factor each has a value of 1.0 for a lightness value, saturation value and hue value converted from a specified color respectively, and monotonically decreases toward 0.0. The modulation amount storage means stores a modulation amount of the lightness value, saturation value, and hue value respectively.The lightness correction means computes a corrected lightness value from the converted lightness value, the saturation correction means computes a corrected saturation value from the converted saturation value, and the hue correction means computes a corrected hue value from the converted hue value by using the first, second, and third correction factors, and the modulation amount. The inverse conversion means inversely converts the corrected lightness value, corrected saturation value, and corrected hue value into a combination of component values of reference colors.