A Robust Wavelet-Based Digital Watermarking Using Statistical Characteristic of Image and Human Visual System

The current paper proposes a wavelet-based digital watermarking algorithm using statistical characteristic of image and human visual system (HVS). The original image is decomposed into 4-level using a discrete wavelet transform (DWT), then the watermark is embedded into the perceptually significant coefficients (PSCs) of the image. In general, the baseband of a wavelet-decomposed image includes most of the energy of the original image, thereby having a crucial effect on the image quality. As such, to retain invisibility, the proposed algorithm does not utilize the baseband. Plus, the wavelet coefficients on the lowest level are also excluded in the watermark-embedding step, because these coefficients call be easily eliminated and modified by lossy compression and common signal processing. As such, the PSCs are selected from all subbands, except for the baseband and subbands on the lowest level. Finally, using the selected PSCs, the watermark is then embedded based on spatial masking of the wavelet coefficients so as to provide invisibility and robustness. Computer simulation results confirmed that the proposed watermarking algorithm was more invisible and robust than conventional algorithms.