Threshold Matrix Dot Dispersion for Pseudo-Outline Suppression
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Solution Overview
Problem
Conventional image forming methods using halftoning techniques struggle to prevent the generation of pseudo-outlines when forming images with two or more types of dots having different densities per unit area within the same hue, leading to discontinuous points and poor image quality.
Innovation Solution
An image forming apparatus and method utilizing a threshold value matrix with a size smaller than the input image, featuring a dot formation determining section that compares pixel values with corresponding threshold values to decide on the formation of dots, with threshold values configured to reduce dot frequency in low and high-density gradation regions, thereby controlling dot density and preventing pseudo-outlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common threshold value matrix is used with uniform distribution of threshold values, then the processing speed is extremely fast and simple dot formation is achieved, but when two or more types of dots with different densities are formed, discontinuous points and pseudo-outlines are generated
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of threshold values in the threshold value matrix. Specifically, threshold values are concentrated in certain regions while being sparser in others, causing different dot formation behaviors in different spatial locations. This local variation in threshold value density enables better control over dot dispersion patterns, preventing pseudo-outlines while maintaining processing efficiency.
Solution Approach 2:
The patent changes the parameter distribution of threshold values from uniform to non-uniform. By adjusting the density and distribution characteristics of threshold values in the matrix, the system achieves better control over dot formation. This parameter change allows the system to maintain high processing speed while improving dot dispersion quality and eliminating pseudo-outlines.
2Device complexity
If threshold values are uniformly distributed in the threshold value matrix, then the structure is simple and easy to implement, but pseudo-outlines are easily generated when forming multiple dot types
Solution Approach 1:
The patent introduces local quality by making the threshold value distribution non-uniform across the matrix. Different regions have different threshold value densities, which creates spatially varying dot formation characteristics. This local differentiation prevents the uniform threshold patterns that cause pseudo-outlines, while the overall matrix structure remains relatively simple.
Solution Approach 2:
The patent applies asymmetry by breaking the uniform symmetry of threshold value distribution. Instead of all threshold values being evenly distributed, the system creates an asymmetric distribution pattern where threshold values are concentrated in certain areas and sparser in others. This asymmetric structure eliminates the periodicity that leads to pseudo-outlines while maintaining implementation simplicity.
3Manufacturing precision
If the number of threshold values is increased to control dot density precisely, then dot density control is improved, but the processing time and computational load increase
Solution Approach 1:
The patent changes the parameter distribution strategy by using a non-uniform distribution of threshold values. Instead of increasing the total number of unique threshold values, the system optimizes the distribution pattern, concentrating threshold values where needed and reducing them where not required. This approach achieves precise dot density control in critical regions while minimizing overall computational load.
Solution Approach 2:
The patent applies local quality by varying the density of threshold values across different regions of the matrix. High-density threshold value regions provide precise dot density control where needed, while low-density regions reduce computational complexity. This spatially adaptive threshold value distribution achieves good dot density control without uniformly increasing processing time across the entire image.
Data Source
AI summary
An image forming apparatus, for forming an image with using distributions of two or more types of dots having different densities per unit area in a same hue, including: a threshold value matrix; and a dot formation determining section for carrying out comparison between a pixel value at a target pixel in the input image and a threshold value corresponding to the target pixel in the threshold value matrix, and for determining, whether to form or not to form any one of the two or more types of dots, wherein threshold values in the threshold value matrix are configured so that a frequency of dot formation is lower, for gradation regions in which a dot density of any of the two or more types of dots is low and/or high, than that for gradation regions in which the dot density is in average level.