A Robust Non-Blind Image Watermarking Method Using 2-Level HWT-DCT

The current technology allows to distribute digital images quickly and easily over the internet. Some digital images have copyright that needs to be protected. Watermarking is a technique for protecting copyright. In order for copyright is not easily lost with image manipulation, then watermarking technique must be robust. This study proposes a combination of Discrete Cosine Transform (DCT) based on two levels of the Haar Wavelet Transform (HWT) on image watermarking method with the aim of improving aspects of robustness and imperceptibility. The first step, host image is transformed with DWT as much as two levels to get LL2 subband. LL2 subband is a subband containing the image core information of two levels of wavelet transformation. Furthermore, LL2 subband split into small sub-blocks with the size of 4 * 4. The sub-blocks are transformed again using DCT. Insertion of watermarks using alpha variables with a certain value on the DC coefficient matrix. This value is used for managing the quality and strength of the watermark. To test the imperceptibility and watermark resistance used measuring instruments MSE, PSNR, and correlation coefficient. Based on the simulation results obtained a watermarked image is quite satisfactory with a relatively good imperceptibility value and resistant to various attacks.