Image Processing Apparatus Threshold Matrix Inversion for Mixed Color Granularity
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Solution Overview
Problem
Existing image processing methods for printing with multiple color materials result in conspicuous granularity, even when using threshold matrices with blue noise characteristics, especially when overlapping dots of high dot power are mixed.
Innovation Solution
An image processing apparatus that generates quantization data for each color based on unique threshold matrices, where the order of pixel positions in one threshold matrix is inverse to the order in another, to ensure high dispersibility and minimize granularity, by comparing gradation data with adjusted thresholds and generating quantization data based on specific conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a common threshold matrix with blue noise characteristics is used for multiple color materials, then good dispersibility is obtained for single-color printing, but conspicuous granularity occurs when multiple colors are mixed
Solution Approach 1:
The patent divides the threshold matrix into multiple separate threshold matrices, one for each color material. Each threshold matrix is independently designed with blue noise characteristics to ensure optimal dispersibility for that specific color, rather than using a single common threshold matrix for all colors.
Solution Approach 2:
The patent applies different threshold matrices to different color materials based on their specific characteristics. Each color material (cyan, magenta, yellow, black) has its own optimized threshold matrix that considers the dot power and printing characteristics of that specific color, allowing local optimization for each color channel.
2Object-affected harmful factors
If threshold shifting is applied to multiple colors to improve dispersibility, then mixed-color granularity is reduced, but dispersibility of individual colors deteriorates
Solution Approach 1:
Instead of shifting thresholds to improve mixed-color printing (which degrades single-color dispersibility), the patent inverts the approach by using separate threshold matrices with inverse relationships. The threshold matrices are designed so that when colors are overlaid, the combined effect produces blue noise characteristics, achieving both good single-color and mixed-color dispersibility without threshold shifting.
3Adaptability or versatility
If dots of multiple color materials are overlaid to expand color expression, then color richness is improved, but dispersibility of overlapping dots deteriorates
Solution Approach 1:
The patent creates a composite threshold system where multiple color-specific threshold matrices work together. When color dots are overlaid, the combination of different threshold patterns from each color material produces a composite effect with blue noise characteristics, maintaining high dispersibility even in overlaid regions while expanding color expression capabilities.
Data Source
AI summary
An image processing apparatus performs image processing to print a color materials of a first color and a second color. When a sum of a first gradation data for the first color and a second gradation data for the second color is equal to or smaller than the maximum value of thresholds of a first threshold matrix, a generation unit generates a second quantization data for the second color based on a result of comparing the second gradation data with a second threshold. When the sum is greater than the maximum value, the generation unit generates third gradation data by subtracting the maximum value from the sum and generates the second quantization data based on a result of comparing the third gradation data with the first threshold or a result of comparing a difference between the second gradation data and the third gradation data with the second threshold.