Document Image Processing for Balanced Resolution and Character Density
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Solution Overview
Problem
Existing image processing systems face challenges in maintaining image quality when reading documents at different resolutions in the main and sub-scanning directions, leading to uneven reproduction of details and potential image deterioration.
Innovation Solution
An image processing apparatus that includes a document reading device and 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
1Quantity of substance
If a document is read at a low resolution to reduce file size, then the file size is reduced, but the image quality and reproducibility of the print deteriorate
Solution Approach 1:
The patent applies different resolution settings to different regions of the document. Character areas are read at a lower resolution (e.g., 300 dpi) while graphic areas are read at a higher resolution (e.g., 600 dpi). This local differentiation allows file size reduction in text-dominated regions while maintaining high image quality in graphic-intensive regions, resolving the contradiction between file size and image quality.
Solution Approach 2:
The patent segments the document into different types of areas (character areas and graphic areas) and processes each segment with appropriate resolution settings. By dividing the document into functional regions and applying tailored resolution conversion, the system achieves optimal balance between file size reduction and image quality preservation for each segment type.
2Manufacturing precision
If a high resolution is used to read the document to improve image quality, then the image quality is improved, but the file size increases
Solution Approach 1:
Instead of uniformly applying high resolution to the entire document, the patent applies high resolution only to graphic areas where it is necessary for quality reproduction. Character areas are processed at lower resolution, thereby maintaining image quality where needed while avoiding unnecessary file size increase in text regions.
3Productivity
If different resolutions are used in main and sub-scanning directions to optimize processing, then processing efficiency is improved, but uneven pixel thinning and image deterioration occur
Solution Approach 1:
The patent performs preliminary classification of document areas into character areas and graphic areas before resolution conversion. Based on this pre-classification, appropriate resolution settings are applied to each area type, preventing uneven pixel thinning and image deterioration that would result from uniform or directionally-biased resolution processing.
Data Source
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AI summary
An image processing apparatus (1) includes an intermediate image generator (101) 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 (5), a character area detector (102) configured to detect a character area within an image represented by the intermediate image data, an image corrector (104) 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 (105) configured to convert the resolution of the corrected intermediate image data into a predetermined output resolution and generate output image data.