Adaptive Digital Watermark Embedding in Printed Colors
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Solution Overview
Problem
Current methods for data hiding in printed colors, particularly spot colors and process colors, face challenges in minimizing visibility and ensuring robustness, especially when integrating digital watermarks into packaging and printed objects, due to limitations in print technology and human visual system sensitivity.
Innovation Solution
The implementation of an adaptive embedding framework that utilizes human visual system models, robustness modeling, and color appearance models to optimize the embedding of digital watermarks in spot colors and process colors, incorporating techniques such as overprinting and spectral reflectance analysis to minimize visibility while ensuring robust signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital watermarks are embedded in printed colors using conventional methods, then data hiding capability is achieved, but visibility of the watermark increases and robustness decreases
Solution Approach 1:
The patent transforms the watermark embedding problem from a single-color modification task into a multi-color coordinate transformation problem. By changing the color space parameters and using adaptive embedding in multiple color channels (CMYK), the system achieves better robustness while controlling visibility through perceptual weighting of different color modifications.
Solution Approach 2:
The patent combines multiple color modifications (Cyan, Magenta, Yellow, Black adjustments) to create a composite watermark embedding approach. Each color channel contributes to the overall watermark signal, and their combined effect provides both robustness against various printing conditions and controlled visibility through human visual system modeling.
2Reliability
If watermark signal strength is increased to improve detection robustness, then robustness improves, but visibility and detectability by human visual system increases
Solution Approach 1:
The patent applies different embedding strengths and strategies to different color channels based on their individual properties and the human visual system's sensitivity to each channel. By locally optimizing the embedding in each CMYK channel according to its characteristics, the system achieves robust overall detection while minimizing visibility in each specific channel.
Solution Approach 2:
The patent uses adaptive parameter adjustment where the embedding strength, color space transformations, and weighting factors are dynamically modified based on the host image content, printing conditions, and detection requirements. This allows optimization of the robustness-visibility tradeoff for each specific application scenario.
3Loss of information
If color modifications are made to embed watermark data, then data hiding capacity increases, but color accuracy and print quality deteriorates
Solution Approach 1:
The patent employs color space transformations (e.g., from RGB to CMYK, and further to alternative color spaces) to find embedding domains where watermark data can be concealed with minimal perceptual impact. By changing the parameter representation of colors, the system achieves higher data capacity while maintaining color accuracy through reversible or imperceptible transformations.
Solution Approach 2:
The patent applies different embedding strategies to different regions and color channels based on local image characteristics and human visual sensitivity. In regions where color accuracy is critical, weaker embedding or alternative methods are used, while in less sensitive regions, stronger embedding provides higher data capacity without noticeable quality degradation.
Data Source
AI summary
The present document provides image processing methods and apparatus. One claim recites: obtaining a signal to be encoded in color image data, the signal comprising a plural-bit payload; predicting a resulting color of overprinting several inks on a substrate, the overprinting representing the color image data encoded with the signal; using the resulting color for both i) visibility evaluation of the overprinting, and ii) signal robustness evaluation of the overprinting as seen by an imaging device. Other claims and combinations are provided.