Robust Image Watermarking Based on DWT-DCT-SVD Against Geometrical Attacks

This paper presents a digital image watermarking algorithm based on Discrete Wavelet Transform-Discrete Cosine Transform-Singular Value Decomposition (DWT-DCT-SVD). DWT based scheme provide scalability, DCT based schemes offers compression and SVD based scheme provide minimum or no distortion. Traditionally it is assumed that for having good robustness, a watermark should be embedded in low or mid frequency. In our method, the main difference from other traditional methods is that the watermark is embedded in high frequency band. DWT is used for finding non-overlapping multi resolution sub-bands. The DCT coefficients of the DWT coefficients of the HH band of DWT are used to embed watermarking information to achieve robustness. SVD had been applied to DCT coefficients of HH band and watermark, Later on the singular values of HH band were modified using singular values of watermark. Robustness is measure of immunity of watermark against attempts to remove or degrade it, intentionally or unintentionally by various types of image processing attacks. Therefore the crucial issue in image watermarking is its robustness to protect digital images from illegal manipulation and against geometric distortions. Simulation results show that the proposed watermarking algorithm based on combined DWT-DCT-SVD gives good performance with respect to robustness against various image processing operations.