Digital Watermark Embedding via Block Frequency Analysis

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Solution Overview

Problem

Current digital watermark technologies lack the ability to detect watermarks at high speed in environments with limited computational resources, such as mobile devices, while tolerating geometric distortion.

Innovation Solution

A digital watermark embedding and detection method that divides images into pixel blocks, spreads watermark information across these blocks as specific frequency waveform patterns, and uses block-by-block processing to amplify and detect the patterns, allowing for robust detection even with geometric distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional digital watermark detection methods are used, then detection accuracy can be maintained, but detection speed is too slow for resource-constrained devices like mobile phones

Engineering Contradiction:

Improvedetection speedVSAvoidcomputational complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent divides the image into multiple pixel blocks and processes each block independently to detect watermark frequencies. This segmentation approach reduces the computational complexity from processing the entire image at once to processing smaller blocks, enabling faster detection on resource-constrained devices while maintaining detection accuracy through block-by-block frequency analysis

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent focuses detection efforts on specific frequency components that are most relevant to watermark detection, rather than analyzing all frequency ranges. By concentrating computational resources on detecting frequencies corresponding to embedded watermarks and using block-by-block processing, the system achieves high-speed detection without sacrificing detection reliability

Inventive Principle:

Principle #16Partial or excessive action

2Measurement precision

If geometric correction is applied to correct camera angle and lens distortion, then detection accuracy improves, but computational resources are consumed and some geometric distortion remains

Engineering Contradiction:

Improvedetection accuracyVSAvoidcomputational resources

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the approach from correcting geometric parameters (camera angle, lens distortion) to detecting watermark frequencies that are inherently robust to geometric transformations. By embedding and detecting watermarks in the frequency domain rather than relying on precise geometric correction, the system achieves detection accuracy without consuming excessive computational resources for correction processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent embeds watermark information in a manner that provides built-in tolerance to geometric distortion before detection occurs. The frequency-based embedding method creates a cushion against geometric transformations, allowing detection to proceed accurately even when perfect geometric correction is not applied, thus reducing the need for computationally intensive correction processes

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Adaptability or versatility

If frequency-based watermark embedding is used, then tolerance to geometric distortion is achieved, but computational complexity increases

Engineering Contradiction:

Improvetolerance to geometric distortionVSAvoidcomputational complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent reduces computational complexity by segmenting the frequency analysis into smaller pixel blocks. Instead of performing complex frequency transformations on the entire image, the system analyzes frequencies in each block independently, making the frequency-based watermarking approach computationally feasible for mobile devices while maintaining geometric distortion tolerance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local frequency analysis to each pixel block rather than global frequency transformation of the entire image. This local approach allows the system to achieve frequency-based watermark embedding with reduced computational requirements, as each block is processed independently with simpler calculations, thereby balancing geometric distortion tolerance with computational feasibility

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7672474B2Electronic watermark embedding device, electronic watermark detection device, method thereof, and program

Publication Date: 2010.03.02 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

A digital watermark embedding apparatus of the present invention includes: a block dividing unit for dividing an input image into plural pixel blocks; a digital watermark information spreading unit for obtaining an embedding series having a length corresponding to a number of divided pixel blocks; a block-by-block embedding unit for selecting at least a frequency from predetermined plural frequencies according to a term value of the embedding series corresponding to a position of a pixel block in the image, amplifying amplitude of a waveform pattern corresponding to the selected frequency with an embedding strength value, and superimposing the waveform pattern in which the amplitude is amplified on the pixel block; and an image outputting unit for outputting an image on which a corresponding waveform pattern is superimposed on each pixel block by the block-by-block embedding unit.