Digital image watermarking technique based on adaptive median filter and HL sub-band of two-stage DWT

摘要

The digital watermarking has capabilities to sort out the matter of copyright degradation, and it is resolved by examining the imperceptibility and robustness of digital images. The robustness against geometric distortions is a crucial issue in the watermarking. In this work, the proposed digital watermarking approach uses an adaptive median filter operation and the HL sub-band of two-stage discrete wavelet transforms (DWT). The cover image has been processed through an adaptive median filter to produce the smooth image. After, one-level DWT is applied to reference and watermark images. We have selected high-frequency HL sub-band for the watermark embedding process. The second stage of DWT has been applied to obtain the modified HL sub-band. The performance of the proposed method is evaluated by computing various measures such as peak signal to noise ratio (PSNR), mean squared error (MSE) and normalised correlation (NC). The proposed method is vigorous in opposition to various attacks, including lossy JPEG compression attack. From the results, it is observed that the proposed method performs better than the recent existing methods.