Abstract
Generally, Laplacian filter is used to make an image more defined and enhanced. In this study, a comparison is toke place between the effects of different places of performing Laplacian filter on the power of the watermark recovery in spatial domain image watermarking. This filter is applied in two different places in the watermark recovery algorithm; before performing the watermark recovery and before take the correlation in the middle of recovery algorithm. The distinction between the watermark and UN water marked parts of the image are increased by this filter. Thus, watermark could recover significantly better by recovery algorithm. We intend to determine which of these places is more appropriate to apply this filter. A typical correlation based method is used as a representative of spatial domain watermarking methods. Several experiment are done to compare the effect of different places in applying proposed filter on quality of extracted watermark in correlation based watermarking algorithm.
Highlights
In recent years, with the expansion of Internet, it becomes very easy to transmit and distribute digital media
The goal of this section is to show the effect of proposed filter on a typical low spatial frequency image
In the noise addition and resize attacks, utilizing Laplacian filter before calculating the correlation better improves the results. As it shown in this table, preforming Laplacian filter before recovery algorithm shows better improvement in the values of Mean Absolute Error (MAE)
Summary
With the expansion of Internet, it becomes very easy to transmit and distribute digital media. The purpose of the watermark is to embed some extra information about the digital data without visibly modifying it (Kasmani and Naghsh-Nilchi, 2008). The imperceptibility means that how much the embedded information makes reductions in signal quality; and the robustness is the ability of the watermark to remain readable after innocent or malicious signal processing operations on the watermarked image. These parameters are incompatible with each other and they should be set to meet the requirements of the application (Kasmani et al, 2009; Kasmani and Naghsh-Nilchi, 2008)
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