Gray Signal Synthesis for Inkjet Printing Density Control
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Solution Overview
Problem
When combining methods to improve gray color stability and dark portion density in inkjet printing, excessive gray ink application can occur in low lightness regions, leading to increased density and decreased printing quality.
Innovation Solution
An image processing method that converts an RGB input signal to a CMYK signal, generates a first Gray signal by substituting CMY values and a second Gray signal with a K value greater than a threshold, and synthesizes these signals with coefficients corresponding to lightness to control gray ink amounts, preventing excessive application and enhancing color stability and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gray ink is added to pixels with high K ink ejection to improve dark portion density, then dark portion density is improved, but gray ink becomes excessive in low lightness regions causing decreased printing quality
Solution Approach 1:
The patent applies different gray ink coefficients to different lightness regions. Specifically, it uses a first coefficient for pixels with lightness above a threshold and a second coefficient for pixels with lightness at or below the threshold. This local differentiation ensures that gray ink is added appropriately in dark portions while preventing excessive application in low lightness regions, thereby resolving the contradiction between improving dark portion density and avoiding harmful excessive gray ink application.
2Stability of the object's composition
If CMY inks are replaced by gray ink using UCR to improve gray color stability, then gray color stability is improved, but gray ink amount increases excessively in some regions
Solution Approach 1:
The patent introduces lightness as a parameter to control the gray ink coefficient. By calculating the lightness of each pixel and comparing it with a predetermined threshold, the system dynamically adjusts the gray ink coefficient between two different values. This parameter-based control allows the system to maintain gray color stability through UCR while preventing excessive gray ink application by adapting the ink amount to the local lightness conditions.
Data Source
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AI summary
An image processing method comprising: converting an RGB input signal to a CMYK signal; converting the RGB input signal to a common color signal including lightness; generating a first Gray signal including a Gray value substituted for CMY values forming gray in the CMYK signal; generating a second Gray signal including a Gray value corresponding to a K value greater than a threshold in the CMYK signal; generating a Gray output signal in a CMYKGray output signal indicating color material amounts of cyan (C), magenta (M), yellow (Y), black (K), and gray (Gray) for printing by multiplying the generated first Gray signal and the generated second Gray signal respectively by coefficients corresponding to the lightness in the common color signal and then synthesizing the first Gray signal and the second Gray signal.