Combined technique for improving digital image watermarking

The technique presented in this paper offers better imperceptibility, reduces execution time and improves robustness in comparison to Discrete Wavelet Transform (DWT), Discrete Cosine Transform (DCT) and hybrid fusion technique (HFT) digital watermarking techniques. The proposed improved technique (IMD-WC-T) combined both the DWT and DCT subsequently and spread the watermark with PN-sequence with a certain key in the DCT transform after decompose the host image with DWT in level 2 to generate the final watermarked image. Such combination allowed us to exploit the individual advantages derivable from the separate use of the DWT and DCT methods. Results obtained from (IMD-WC-T) showed improved performance in terms of imperceptibility, execution time and certain aspect in robustness (Gama Correction, Histogram Equalization) than that of DWT, DCT, and hybrid fusion technique (HFT), in addition to the quality of recovered watermark image as well. Comparing with HFT, the IMD-WC-T technique guarantees additional imperceptibility, reduced execution time and gave more robustness against Gama Correction and Histogram Equalization.