Color Conversion Table Generation via Coordinate Inversion

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Solution Overview

Problem

Conventional image processing apparatuses face issues with color mixing and wasteful toner consumption due to non-linear color gradations in the Lab space, leading to mismatched color gamuts between input and output systems, especially when reproducing fundamental colors.

Innovation Solution

The method involves correcting calculation target points by moving the positions of maximum gradations and gradations of fundamental colors from the output system to match those of the input system, ensuring accurate color conversion without linear interpolation, thereby eliminating color mixing and optimizing toner usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional color conversion methods are used, then color gamut compression is achieved, but color mixing occurs and toner consumption increases

Engineering Contradiction:

Improvecolor reproduction accuracyVSAvoidtoner consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent inverts the conventional color conversion approach by moving calculation target points from the output system (CMYK) to the input system (RGB) coordinate systems. Instead of converting RGB to CMYK directly with potential color mixing, the method transforms output CMYK values back to RGB space, adjusts them to match input system characteristics, and then converts to final output values. This inversion eliminates color mixing while maintaining color gamut compression and reducing toner consumption.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies parameter changes by adjusting calculation target points in the Lab color space to match the characteristics of the input scanning system. By modifying the coordinate system parameters and transformation matrices based on the specific input device characteristics, the method achieves accurate color reproduction without color mixing, thereby reducing unnecessary toner usage while maintaining quality.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If linear interpolation is used for color conversion, then computation is simplified, but color mixing occurs in fundamental colors

Engineering Contradiction:

Improvecomputation simplicityVSAvoidcolor reproduction precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional linear interpolation approach by moving calculation target points from the output CMYK space to the input RGB space. This inversion allows for more precise color matching by utilizing the input system's color characteristics directly, eliminating the color mixing that occurs with conventional linear interpolation while maintaining computational feasibility through systematic point transformation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces the Lab color space as an intermediary transformation layer between the input RGB system and output CMYK system. By transforming through Lab space and adjusting calculation target points in this intermediate representation, the method achieves precise color reproduction without direct linear interpolation between RGB and CMYK, thereby eliminating color mixing while maintaining computation simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If color gamut compression is applied, then output device compatibility is improved, but color mixing increases

Engineering Contradiction:

Improveoutput device compatibilityVSAvoidcolor mixing

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional color gamut compression approach by moving calculation target points from the output CMYK space to the input RGB space. This inversion allows the method to respect the input system's color characteristics while still achieving output device compatibility. By transforming through the inverted coordinate systems and adjusting target points accordingly, the method maintains color gamut compression benefits while eliminating color mixing that would otherwise occur.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS7787149B2Method of generating color conversion table, information generation apparatus, recording medium, and image processing apparatus

Publication Date: 2010.08.31 KONICA MINOLTA BUSINESS TECH INC

AI summary

A color conversion table for converting M color signals of an input system into N color signals of an output system is disclosed. The color conversion table is prepared by and obtained based on a calculation target point corrected by moving a position of the maximum gradation of each fundamental color of the output system to a position of the maximum gradation of the fundamental color of the input system and on calculation target points corrected for gradations other then the maximum gradation of each fundamental color by moving positions of the gradations of the fundamental color in output system to the positions of the gradations of the fundamental color in the input system.