Document Image Resolution Conversion for Uniform Character Density
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Solution Overview
Problem
Existing image processing systems face challenges in maintaining image quality when documents are read at different resolutions in the scanning directions, leading to differences in reproducibility and quality between the main and sub-scanning directions.
Innovation Solution
An image processing apparatus that includes a document reading device and a control device, which performs resolution conversion, detects character areas, and adjusts image densities to balance pixel thinning across both scanning directions, ensuring consistent image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a document is read at a low resolution to reduce reading time and data volume, then productivity is improved, but manufacturing precision deteriorates due to pixel thinning and image quality degradation
Solution Approach 1:
The patent applies preliminary action by performing resolution conversion on the read image data before output. The resolution conversion process interpolates pixels in the sub-scanning direction to match the main scanning direction resolution, thereby preventing pixel thinning and maintaining image quality before the final output stage. This preliminary processing ensures that even when reading at lower resolutions for speed, the final output maintains high quality.
2Manufacturing precision
If the resolution in the sub-scanning direction is increased to match the main scanning direction, then manufacturing precision is improved, but use of energy increases due to higher data volume and processing requirements
Solution Approach 1:
The patent applies local quality by selectively adjusting resolution only in the sub-scanning direction where pixel thinning occurs, while maintaining the original main scanning direction resolution. The resolution conversion process specifically interpolates pixels along the sub-scanning direction lines, applying processing only where needed rather than uniformly across the entire image. This localized approach improves image quality in the affected area while minimizing overall processing power consumption.
3Manufacturing precision
If a high resolution is used to read the document, then manufacturing precision is improved, but productivity deteriorates due to increased reading time and data volume
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the resolution parameters based on the scanning direction. The system reads documents at potentially lower resolutions for speed, then applies resolution conversion that changes the effective resolution parameters in the output by interpolating pixels in the sub-scanning direction. This parameter transformation allows the system to achieve high effective resolution output without requiring high resolution input, thereby maintaining both productivity and image quality.
Data Source
AI summary
An image processing apparatus includes an intermediate image generator configured to generate intermediate image data with the same resolution in both scanning directions by performing resolution conversion on read image data obtained by reading a document with a document reading device, a character area detector configured to detect a character area within an image represented by the intermediate image data, an image corrector configured to correct the intermediate image data so that a density of low-density character areas having a density lower than a predetermined reference density is increased and a density of high-density character areas having a density higher than the reference density is decreased in the character area, and an output image generator configured to convert the resolution of the corrected intermediate image data into a predetermined output resolution and generate output image data.