Robust Image Watermarking in Wavelet Domain using RDWT-HD-SVD and Whale Optimization Algorithm

In the current digital era, the advent of photo editing software and digital media platforms has simplified the process of disseminating images through self-published channels. Nevertheless, the widespread availability of such tools has concurrently facilitated unauthorized image manipulation and alteration. Consequently, safeguarding digital images from copyright infringement has emerged as a critical necessity. Presently, digital watermarks serve as the principal mechanism for protection. Within this context, our paper introduces a novel and robust watermarking algorithm. To reinforce the security of the original watermark, the proposed watermarking algorithm incorporates the scrambling of both the host and the watermark images using the Arnold chaotic map. Initially, the host image is processed through the Redundant Discrete Wavelet Transform (RDWT), resulting in four equally sized sub-bands. Subsequently, Hessenberg decomposition is applied to the LL sub-band, followed by Singular Value Decomposition (SVD) on the resultant matrix. An intensity factor, optimized for each image via the Whale Optimization Algorithm (WOA), is employed to enhance robustness while adhering to a pre-established quality benchmark. This optimization seeks a balance between the invisibility of the watermark and the integrity of the image, thereby resolving the trade-off between imperceptibility and robustness. To evaluate the effectiveness of our scheme, we employ both qualitative and quantitative metrics, including Peak Signal Noise Ratio (PSNR), Structural Similarity Index Metric (SSIM), and Normalized Cross-Correlation (NC). Upon conducting experiments against varied image processing attacks, the results indicate a superior performance of our proposed scheme in comparison to extant watermarking methods.