Abstract
Digital watermarking has become an essential and important tool for copyright protection, authentication, and security of multimedia contents. It is the process of embedding a watermark in the multimedia content and its extraction. Block-based discrete cosine transform (DCT) is a widely used method in digital watermarking. This paper proposes a novel blind image watermarking scheme developed in the spatial domain by quantization of invariant direct current (DC) coefficients. The cover image is redistributed and divided into non-overlapped square blocks and then the DC coefficients invariant to rotation, row and column flip operations, without utilization of the DCT transform, are directly calculated in the spatial domain. Utilizing the quantization parameter and watermark information, the modified DC coefficients and the difference between DC and modified DC coefficients are calculated to directly modify the pixel values to embed watermark bits in the spatial domain instead of the DCT domain. Optimal values of the quantization parameter, which plays a significant role in controlling the tradeoff between robustness and invisibility, are calculated through differential evolution (DE), the optimization algorithm. Experimental results, compared with the latest similar schemes, demonstrate the advantages of the proposed scheme.
Highlights
Advancements in multimedia technologies and computer networks have made duplication and distribution of digital contents such as audio, video or digital images, much easier than ever before in recent years
A redistributed invariant discrete wavelet transform (RIDWT) image watermarking technique was introduced by Li et al [17]. This transform is invariant to the ninety-degree multiple rotations, row, and column flipping and is obtained by shifting the pixels of the image to the new locations and applying wavelet transform and some normalization process. It can be identified from the literature review of discrete cosine transform (DCT)-based image watermarking schemes that, generally, the watermark is inserted into the host image in the frequency domain by modifying the frequency coefficients [10,11]
The host image is divided into blocks, direct current (DC) values are calculated in the spatial domain without using DCT and modified using the optimal quantization parameter obtained through the differential evolution (DE) algorithm to get the new DC values
Summary
Advancements in multimedia technologies and computer networks have made duplication and distribution of digital contents such as audio, video or digital images, much easier than ever before in recent years. This transform is invariant to the ninety-degree multiple rotations, row, and column flipping and is obtained by shifting the pixels of the image to the new locations and applying wavelet transform and some normalization process It can be identified from the literature review of DCT-based image watermarking schemes that, generally, the watermark is inserted into the host image in the frequency domain by modifying the frequency coefficients [10,11]. The host image is divided into blocks, DC values are calculated in the spatial domain without using DCT and modified using the optimal quantization parameter obtained through the differential evolution (DE) algorithm to get the new DC values. Concluding remarks and future research directions are given in the last section
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