Performance of a Hybrid DCT - DT CWT Digital Watermarking against Geometric and Signal Processing Attacks

This paper compares different robust techniques used for imperceptible watermarking, which are resistant to geometric and signal processing attacks. The dual tree complex wavelet transform (DT CWT) provides a means of producing solutions for robust watermarking. Complex wavelet transforms use Gabor real time filters having the properties of shift invariance and directional selectivity. This produces a considerable reduction in the complexity making the DT CWT an ideal solution for real time watermarking. The discrete cosine transform (DCT) has also been proposed for robust watermarking because of its resistance to geometrical attacks. In this paper a hybrid system comprising the DCT and DT CWT is used in order to produce a more robust technique for watermarking. In the process of embedding a watermark, the properties of a human visual system (HVS) are also considered. This paper compares the watermarking process for DT CWT, DT CWT with DCT and discrete wavelets transform (DWT) in producing robust watermarks. This paper demonstrates the superior performance in the presence of geometric and signal processing attacks of the hybrid DT CWT-DCT technique.