Image Processing Apparatus for Accurate Character Color Reproduction
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Solution Overview
Problem
Conventional image processing methods fail to accurately reproduce character colors when compressing color images, often resulting in characters being represented by a different color due to binarization and compression techniques, especially when multiple colors are present in a character region.
Innovation Solution
An image processing apparatus and method that converts multivalued images to binary images, determines character and non-character regions, extracts representative colors for each character region, and adjusts binary images to match the closest representative color to the target pixel color, ensuring accurate color reproduction during compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a binary image is generated from a multivalued image using projection histograms, then compression rate is improved, but character color reproduction accuracy deteriorates
Solution Approach 1:
The patent segments the character clipped area into multiple sub-areas based on color distribution. By dividing the area and generating separate projection histograms for each sub-area, the method can identify multiple candidate character colors instead of a single color, thereby resolving the contradiction between compression and color accuracy.
Solution Approach 2:
The patent changes the parameter approach by not only using the number of black pixels but also incorporating color information (RGB values) into the histogram analysis. This allows the system to determine multiple candidate colors and select the most appropriate one, improving color reproduction while maintaining compression efficiency.
2Device complexity
If one representative color is assigned to each character clipped area, then device complexity is reduced, but manufacturing precision of color reproduction deteriorates
Solution Approach 1:
The patent introduces a dynamic approach where the number of representative colors is not fixed at one but can vary (one or more colors) based on the actual color distribution in each character clipped area. This dynamic adaptation allows the system to maintain low complexity for single-color characters while accurately handling multi-color characters.
Solution Approach 2:
The patent changes the parameter from a single representative color to multiple candidate representative colors. By calculating and storing multiple candidate colors with their respective frequencies, the system can select the most appropriate color(s) based on the actual character content, improving precision without significantly increasing complexity.
Data Source
AI summary
An image processing apparatus converts a multivalued image to a binary image, determines a character region and a non-character region in the binary image, extracts areas in units of a character from the character region, determines whether each of the areas is a character region or a non-character region, and extracts, for each of the areas determined to be the character region, a first representative color from the multivalued image included in the area, and generates a binary image corresponding to the first representative color. The apparatus decides a second representative color closest to a color of a target pixel by comparing the first representative color with the color of the target pixel, and changes the binary image of the area corresponding to the first representative color to a binary image of the decided second representative color.