Differential evolution algorithm for the selection of optimal scaling factors in image watermarking

In this paper, an innovative watermarking scheme based on differential evolution (DE) in the transform domain is proposed. The insertion and extraction of the watermark are performed in discrete wavelet transform-singular value decomposition (DWT–SVD) transform domain. In the embedding process, the host image is transformed into sub-bands of different frequencies by third-level DWT and then subsequent application of SVD on low pass (LL) and high pass (HH) sub-bands at level third. The watermark image is properly scaled down by multiplying with different scaling factors (SFs) and embedded in the Singular value matrix of LL and HH sub-bands of the host image to make the watermark invisible and robust. We applied an optimization technique, differential evolution, to search optimal scaling factors to improve the quality of watermarked image and robustness of the watermark. In order to overcome the false positive problem, a binary watermark is also embedded in the host image in a lossless manner. According to the numerical results, the quality of watermarked image is satisfactory and embedded watermark is extracted successfully even if the watermarked image is exposed to various image processing and geometric attacks.