Block-Based Image Watermarking for Cropping-Resistant Tracking
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Solution Overview
Problem
Images are often subject to unauthorized use, and existing methods struggle to effectively embed and detect watermarks that can withstand modifications such as cropping and format conversion while remaining imperceptible to the human eye.
Innovation Solution
A pipeline-based approach for digital watermarking that includes preprocessing stages for images and information, using techniques like feature detection, frequency transformation, and channel encoding to embed a decentralized identifier in blocks of the image, ensuring robustness and imperceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If watermarking methods are made more robust to withstand modifications like cropping and format conversion, then the watermark's ability to survive image modifications improves, but the complexity of the embedding and detection system increases
Solution Approach 1:
The patent divides the image into multiple blocks and embeds watermark bits across different blocks. Each block is processed independently through frequency transformation and quantization, allowing the watermark to be distributed throughout the image. This segmentation enables robustness against cropping and format conversion while maintaining manageable processing complexity for each block.
Solution Approach 2:
The patent transforms image blocks from spatial domain to frequency domain using discrete cosine transformation (DCT), embeds the watermark in the frequency domain, and then transforms back. This dimensionality change to frequency domain allows the watermark to be embedded in a representation that is more resilient to spatial modifications like cropping and format conversion.
2Manufacturing precision
If the watermark is made imperceptible to the human eye, then the visual quality of the watermarked image improves, but the detectability and reliability of watermark detection deteriorates
Solution Approach 1:
The patent applies different quantization strengths to different frequency coefficients and different blocks based on their local characteristics. Blocks with higher energy or importance to visual quality receive different treatment than less significant blocks. This local quality approach allows the watermark to be embedded with varying strength across the image, maintaining imperceptibility in visually sensitive areas while ensuring detectability in less sensitive areas.
Solution Approach 2:
The patent modifies image parameters (pixel values in frequency domain) by small amounts that are imperceptible to human vision but sufficient for reliable watermark encoding. The quantization step changes parameter values in a controlled manner that preserves visual quality while embedding detectable watermark information through systematic parameter modifications.
3Reliability
If multiple blocks are used to embed each set of bits for robustness, then the watermark survives image modifications better, but the time and computational resources required for embedding and detection increase
Solution Approach 1:
The patent segments both the image and the watermark information into manageable blocks and bits. By dividing the watermark into multiple sets of bits distributed across multiple image blocks, the system achieves robustness through redundancy while keeping individual processing units small and efficient. This segmentation allows parallel processing and reduces the computational burden on any single processing element.
Solution Approach 2:
The patent performs preprocessing steps including image blocking, frequency transformation, and bit assignment before the actual watermark embedding. These preliminary actions organize the data structures and prepare the image blocks in advance, reducing the computational complexity during the detection phase. The preprocessing enables faster detection by having the data ready in an optimized format.
Data Source
AI summary
Provided is a method and apparatus for digital image watermarking. In the method and apparatus, a computer system receives a first image and receive information for embedding in the first image. The computer system preprocesses the first image to produce a preprocessed first image and preprocesses the information by at least channel-encoding the information to produce preprocessed information including a plurality of sets of bits. The computer system embeds the preprocessed information in the preprocessed first image by at least selecting a plurality of blocks of the preprocessed first image and embedding in each block of the plurality of blocks a respective set of bits of the plurality of sets of bits. Each set of bits of the plurality of sets of bits is embedded in a minimum number of blocks of the plurality of blocks, where the minimum number of blocks is greater than one.