Image Processing Device Blue Noise Dot Placement Graininess
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Solution Overview
Problem
Inkjet printing using multiple colors results in overlapping dots with high dot power, leading to increased graininess in images, as existing inter-color processing methods do not adequately address the dispersivity of overlapping dots.
Innovation Solution
An image processing method that performs multinary color conversion and inter-color processing by arranging dots in descending order of dot power, using a threshold matrix with blue noise characteristics to optimize dot placement and reduce graininess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If inter-color processing is performed using a threshold matrix with blue noise characteristics, then dispersiveness of single-color dots is improved, but graininess increases due to overlapping dots with high dot power
Solution Approach 1:
The patent changes the parameter of threshold assignment by introducing a threshold offset value that varies according to the combination of ink colors. Instead of using a fixed threshold matrix for all color combinations, the system adjusts the threshold parameters dynamically based on which inks are overlapping, thereby controlling the dispersiveness and dot power characteristics to reduce graininess.
Solution Approach 2:
The patent applies different threshold offset values to different color combinations locally. Each pixel's quantization threshold is adjusted based on the specific combination of ink colors present at that location, allowing the system to optimize dispersiveness and minimize graininess for each local color combination rather than using a uniform approach.
2Stability of the object's composition
If dots are arranged at pixel positions corresponding to consecutive thresholds, then blue noise characteristic is enhanced, but overlapping dots with high dot power make graininess stand out
Solution Approach 1:
The patent modifies the threshold parameter by adding an offset value that depends on the ink color combination. This parameter change allows the system to maintain the blue noise characteristic through consecutive threshold assignment while simultaneously adjusting the effective threshold to control overlapping dot behavior and reduce graininess.
Data Source
Figure 1~1(b)
Figure 2
Figure 3
AI summary
Multiple first gradation values corresponding respectively to the multiple inks are quantized to generate multiple first quantized values indicating printing or non-printing of dots with the respective inks. In this case, multiple second gradation values corresponding respectively to multiple multinary colors expressible by combinations of overlapping of the multiple inks are generated based on the first gradation values. Next, the multiple second gradation values are quantized to generate multiple second quantized values indicating printing or non-printing of dots of the respective multinary colors. Then, the first quantized values corresponding to the inks to be overlapped one on top of another to express the multinary colors are generated based on the second quantized values corresponding respectively to the multiple multinary colors.