Image Color Conversion Using Region-Based Gamut Mapping
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Solution Overview
Problem
Existing color mapping methods in printers can cause color degeneration by either degrading chroma or failing to maintain color differences, especially when colors are outside the printer's color gamut, leading to inappropriate color conversion results.
Innovation Solution
An image processing apparatus that detects regions of uniform color in an image and applies different color conversion tables based on the number of colors present, increasing color differences between colors to maintain perceptual accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If colorimetric mapping is performed, then color accuracy is improved, but color degeneration occurs when colors are outside the printer's color gamut
Solution Approach 1:
The patent applies different color conversion methods (colorimetric vs. perceptual) to different regions of the image based on local color characteristics. By detecting regions with colors outside the printer's gamut and applying perceptual mapping specifically to those regions, the system maintains color accuracy where possible while preventing color degeneration in problematic areas.
Solution Approach 2:
The system dynamically selects between colorimetric and perceptual mapping methods based on the specific color values present in the image. Rather than using a fixed conversion method for the entire image, the patent adjusts the conversion approach locally depending on whether colors fall within or outside the printer's color gamut, optimizing both accuracy and reliability.
2Reliability
If perceptual mapping is performed, then color degeneration is reduced, but chroma is degraded even when colors are reproducible
Solution Approach 1:
The patent applies perceptual mapping only to specific regions where it is needed (colors outside the printer's gamut), while leaving other regions to use colorimetric mapping. This localized application preserves chroma accuracy for reproducible colors while still preventing color degeneration where necessary.
Solution Approach 2:
The system dynamically determines which regions require perceptual mapping based on color gamut analysis. By switching between mapping methods based on local color characteristics, the patent maintains chroma accuracy for reproducible colors while applying perceptual correction only where color degeneration would occur.
3Productivity
If color conversion is performed on partial document pixels, then processing speed is improved, but color distance between susceptible colors cannot be increased sufficiently
Solution Approach 1:
The patent focuses color distance adjustment on specific regions identified as having colors outside the printer's gamut, rather than processing all pixels uniformly. This localized approach maintains color distinctions where needed while improving overall processing efficiency by avoiding unnecessary processing of already-reproducible colors.
Solution Approach 2:
The system segments the image into different processing zones based on color characteristics, applying different conversion strategies to different segments. This segmentation allows efficient processing of large images while maintaining color accuracy in critical regions through targeted color distance adjustment.
Data Source
AI summary
An image processing apparatus is configured to detect one or more regions each of which has a predetermined size configured by pixels of the same color from image data, store color information of a color included in each of the one or more regions detected, and generate output image data by performing color conversion of the image data using a first color conversion table in a case where the color information stored indicates one color, and generate output image data by performing color conversion of the image data using a second color conversion table in a case where the color information stored is two or more colors. Color conversion using the second color conversion table results in a larger color difference between at least two colors in the color information than color conversion using the first color conversion table.