Self-adaptive step firefly algorithm based robust watermarking method in DWT-SVD domain

Digital image watermarking, a data hiding method has become widespread to prohibit illegal use of personal files lately. In this study, a robust Discrete Wavelet Transform (DWT) and Singular Value Decomposition (SVD) based technique is proposed for copyright protection. The cover image is firstly decomposed into sub-bands by DWT. Low frequency sub-band is then divided into non-overlapping blocks. Blocks where watermark will be embedded are selected depending on their standard deviation values. Selected blocks are transformed to U, S, and V matrices by SVD. Watermark is embedded into the second row value in the first column of U component obtained by SVD. Embedding scaling factor is determined by Self-Adaptive Step Firefly Algorithm (SASFA) to balance robustness and transparency that are contradictory to each other. Firefly Algorithm (FA) is a simple, easy to implement, and flexible algorithm but it can pass over the global optimum or get trapped at local optimum. Therefore, SASFA, which constitutes the next step of each firefly based on its previous and present situations is used for global exploration of the solution space. Fibonacci-Lucas Transform (FLT) is applied to binary watermark to provide the security of watermarking scheme. Achieved scrambled watermark bits are used in embedding process. Performance of the proposed scheme is measured by using Bit Error Rate (BER), Normalized Correlation (NC), and Peak Signal-to-Noise Ratio (PSNR). Experimental results prove that the method has high robustness level against attacks and a good visual quality.