DWT-SVD based Digital Image Watermarking using Swarm Intelligence

In this paper, a digital image watermarking technique based on Discrete Wavelet Transform (DWT) and Singular Value Decomposition (SVD) is proposed. For embedding the watermark, cover image is decomposed into different subbands using 2-level DWT. SVD is applied on both medium frequency subbands after 2-level decomposition of cover image. A watermark image is splitted into two equal images on column basis. These images are again resized to the size of original watermark image by zero padding. The singular value matrices of medium frequency subbands of cover image are modified by splitted watermark images using suitable scale factor obtained by Particle Swarm Optimization (PSO). Again SVD is applied on these modified singular value matrices. Inverse SVD is applied on these singular value matrices along with respective orthogonal matrices of subbands to recover the modified wavelet subbands. The Inverse DWT on these modified subbands along with remaining subbands of cover image makes the watermarked image. Extracted spitted watermark images are added together to reconstruct the original watermark. The Analysis and experimental results show that the proposed technique is more robust against common image manipulation attacks.