An Improved Approach to Robust Digital Image Watermarking Algorithm Using Lifting Wavelet Transform Technique for Copyright Protection

Abstract

This research work has developed a robust digital image watermarking algorithm using lifting wavelet transform technique for copyright protection to address the problem of watermark distortion during embedding and extracting processes and easy removal of watermark. The improvement in this work is predicated on the replacement of conventional discrete wavelet transform with lifting wavelet transform for more efficient decomposition and minimal embedding and extraction time without significant trade-off in the performance indices as compared to other image watermarking algorithms that used 2-D transformation such as DWT, DCT, SVD or combination of two or all of these transform methods for image transformation. These transforms have been identified to possess limited properties that make them less efficient. The watermark embedding was carried out by embedding the watermark in the Lifting Wavelet Transform (LWT) coefficients of each 2 x 2 blocks decomposed. The algorithm was implemented using MATLAB R2013a software and evaluated using Peak Signal to Noise Ratio (PSNR) and Normalized Correlation (NC). Based on the simulation results obtained, the improved model gave robustness improvement of 18.83%, 54.33% and 59.93% for Jpeg compression attack, cropping attack, and Gaussian noise attack respectively. A Peak Signal to Noise Ratio (PSNR) of 38.4073dB was obtained representing 2.64% imperceptibility improvement. These indicate that the improved model has better performance. Furthermore, the simulated result of the improved model were validated using ITUT-T JI47 recommendations benchmark of < 1 for Normalized Correlation (NC) when subjected to attacks and Peak Signal to Noise Ratio (PSNR) of 35dB or above for good robustness and imperceptibility respectively.