Dither Matrix Sub-Matrix Arrangement for Fine Line Preservation
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Solution Overview
Problem
Thresholding processes often result in the disappearance of fine lines and difficulties in rendering small text due to low-level values, as existing dithering techniques fail to effectively handle images with multiple angled fine lines and low-level text without compromising image quality.
Innovation Solution
An image processing apparatus utilizing a dither matrix with sub-matrices arranged in a specific pattern to ensure that only one dot region is present in each row and column, and that dots are distributed to maintain 2×2 cell blank regions, preventing the collapse of these regions and ensuring even dot distribution, thereby preserving fine lines and text quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional dither matrix is used for thresholding, then the processing is simple, but fine lines at low-level values disappear and image quality deteriorates
Solution Approach 1:
The dither matrix is divided into multiple sub-matrices (e.g., four 4×4 sub-matrices), where each sub-matrix contains dot regions with specific threshold values. This segmentation allows different regions to handle different density levels independently, preventing fine lines from disappearing while maintaining processing simplicity.
Solution Approach 2:
Each sub-matrix has dot regions with specifically designed threshold values that vary locally. The threshold values are arranged so that lower thresholds appear in regions needing finer detail, while higher thresholds appear in regions needing coarser detail. This local differentiation ensures fine lines are preserved without compromising overall image quality.
2Manufacturing precision
If the screen angle is changed to handle fine lines, then some fine lines are preserved, but text rendered in low-level values becomes difficult to read
Solution Approach 1:
Instead of changing the screen angle, the invention changes the threshold values within the dither matrix. By carefully selecting and distributing threshold values across multiple sub-matrices, the system preserves fine lines through threshold-based control rather than angular adjustment, avoiding the problem of text becoming unreadable.
3Manufacturing precision
If dot regions are densely packed to improve resolution, then fine lines are better reproduced, but 2×2 cell blank regions collapse and image quality worsens
Solution Approach 1:
The dither matrix is segmented into sub-matrices with controlled dot distributions. Each sub-matrix maintains a structured arrangement where 2×2 cell blank regions are preserved by limiting the density of dot regions within each sub-matrix. This segmentation prevents blanket collapse while maintaining sufficient resolution.
Solution Approach 2:
Dot regions are distributed non-uniformly across different sub-matrices based on local requirements. Some sub-matrices have higher dot density for fine line reproduction, while others maintain lower density to preserve blank regions. This local quality differentiation balances resolution needs with structural stability.
Data Source
AI summary
An image processing apparatus includes a storage unit and a converting unit. The storage unit stores a dither matrix including a plurality of sub-matrices. Each sub-matrix has a group of dot regions and each dot region has a threshold value. The dot regions are arranged in N rows and N columns in which N is an integer greater than or equal to 4 and the dot regions define a first diagonal line and a second diagonal line. Each sub-matrix has a plurality of first orthogonal lines extending in a direction parallel to the first diagonal line and a plurality of second orthogonal lines extending in a direction parallel to the second diagonal line. N dot regions whose threshold value is smaller than a prescribed value are contained in the group of dot regions. Only one of N dot regions is contained in each row and each column. At most one of N dot regions is contained in each first orthogonal line and each second orthogonal line. The converting unit is configured to convert print data into binary data by using the dither matrix.