Digital Watermark Embedding in Multi-gradation Images
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Solution Overview
Problem
Conventional digital watermark techniques face challenges in restoring sub-information from multi-gradation images, particularly in regions of high concentration, where image quality is deteriorated, leading to degraded restorability of embedded data.
Innovation Solution
An image processing method that involves preprocessing and post-processing of multi-gradation images using a gradation correction process based on the relationship between certain image data and read image data, embedding sub-information using a digital watermark technique that increases color difference in high concentration regions while maintaining it in intermediate concentration regions to enhance restorability without degrading image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sub-information is embedded in high concentration regions using conventional digital watermark techniques, then the embedding process is simple, but the restorability of sub-information is degraded due to image quality deterioration
Solution Approach 1:
The patent applies different embedding strategies to different concentration regions. In high concentration regions, sub-information is embedded using color-difference components with adjusted color difference amounts that account for image quality deterioration. In intermediate concentration regions, standard embedding is used. This local differentiation resolves the contradiction by optimizing embedding for each region's specific characteristics.
Solution Approach 2:
The patent changes the color difference amount parameter dynamically based on the concentration region. For high concentration regions, the color difference amount is adjusted (increased or modified) to compensate for the deteriorating image quality, thereby maintaining restorability. This parameter adaptation allows the system to maintain reliability while preserving ease of embedding.
2Reliability
If color difference amount is increased in high concentration regions to improve restorability, then sub-information restorability is improved, but image quality deterioration is exacerbated
Solution Approach 1:
The patent precisely adjusts the color difference amount parameter in high concentration regions to an optimized value that balances restorability and image quality. By calculating and applying the appropriate color difference amount based on the specific characteristics of high concentration regions, the system achieves high restorability without excessive image quality deterioration.
Solution Approach 2:
The patent dynamically determines the color difference amount based on the concentration region being processed. The system adapts the color difference parameter in real-time according to the image data characteristics of each region, allowing optimal balance between restorability and image quality maintenance.
3Device complexity
If conventional digital watermark techniques are used without region-specific processing, then the processing flow is simple, but restorability varies depending on the color and concentration of the main image
Solution Approach 1:
The patent segments the image into different concentration regions (high concentration and intermediate concentration regions) and applies region-specific embedding processes to each. This segmentation allows the system to maintain consistent restorability across different image regions while managing complexity through structured regional processing.
Solution Approach 2:
The patent implements local quality processing by treating different concentration regions with different embedding parameters and methods. This ensures that sub-information restorability is optimized for each region's specific characteristics, achieving consistent overall restorability while maintaining processing manageability through clear regional differentiation.
Data Source
AI summary
A multi-gradation image such as a face image of a person in which sub-information is to be embedded is subjected to a preprocess by a preprocessing section based on a relationship between certain image data and read image data of a printed matter on which the certain image data is printed, sub-information is embedded into the multi-gradation image subjected to the preprocess by the preprocessing section by use of an digital watermark embedding section in an invisible state to the human eye, and the multi-gradation image having the sub-information embedded therein by the digital watermark embedding section is subjected to a post-process corresponding to the preprocess performed by the preprocessing section by use of a post-processing section.