Elevating watermark robustness by data diffusion in Contourlet coefficients

Abstract

As concerns about copyright protection increased amongst multimedia owners in recent years, many watermarking algorithms proposed to protect copyright of digital images. These methods are either spatial or frequency domain techniques. It is essential for a watermarking method to have acceptable robustness. That is why many existing methods try to improve their robustness against signal processing modifications. In this paper a block based watermarking scheme is proposed that embeds a binary logo into Contourlet coefficients of image. To increase robustness, embedding is done in two scales and watermark is inserted into DCT coefficients of Contourlet blocks to diffuse the effects of the embedding throughout the coefficients. Experimental results, and comparison with a robust Contourlet domain method, show that the proposed scheme has better robustness against some image processing attacks, while improving fidelity. Furthermore the proposed algorithm has the advantage of having a blind extraction phase.

Cascaded transform space watermarking based on analysis of local entropy variation

“…To evaluate our method we compared it with two state of the art algorithms of [7] and [13]. Both of these two recent algorithms use CT for embedding purposes and are considered as comparable with our method.…”

“…To evaluate the performance of the proposed watermarking scheme, we compare both the visual quality and robustness of our method with two comparable methods which use the same transform domain and use binary logo as watermark [7] [13]. Method of [7] is a non-blind CTbased watermarking scheme that uses two scales of CT and also uses 32×32 binary logo as watermark.…”

“…Method of [7] is a non-blind CTbased watermarking scheme that uses two scales of CT and also uses 32×32 binary logo as watermark. To justify our scheme, we implement a recent hybrid DCT-CT based method that is presented in [13]. Figure 4 illustrates original and watermarked images for "Lena".…”

“…Suppose the approximate scale of an image in the first level of CT is to be partitioned into ‫ܮ‬ × ‫ܮ‬ blocks. Hence, the maximum number of blocks in the approximate scale will be Among the steps of the proposed method, step 5 has a critical role in enhancing the robustness and imperceptibly of our method while extending capacity of the host image as compared to a recent comparable contourlet based method proposed in [13]. The strength factor (ߙ) for each block depends on the difference between complexities of this block and its adjacent one.…”

“…The method presented in [11] uses singular values of wavelet coefficients and the method in [12] uses singular values of CT coefficients. There are also methods that embed watermark in DCT coefficients of CT. To elevate robustness, [13] presented another hybrid method that uses DCT coefficients of contourlet transform and thus distributes effects of the embedding by diffusion throughout CT coefficients. In [14] a non-blind watermarking algorithm is proposed for embedding information into medical images.…”