A visible watermarking algorithm based on the content and contrast aware (COCOA) technique

A novel visible watermarking algorithm based on the content and contrast aware (COCOA) technique with the consideration of Human Visual System (HVS) model is presented in this study. In order to determine the optimal watermark locations and strength at the watermark embedding stage, the COCOA visible watermarking utilizes the global and local characteristics of the host and watermark images in the discrete wavelet transform (DWT) domain. To achieve the best tradeoff between the embedding energy of watermark and the perceptual translucence, the utilization of contrast–sensitive function, noise visible function of perceptual model, and the basis function amplitudes of DWT coefficients are fine tuned, for the best quality of perceptual translucence and noise reduction of the COCOA algorithm. The experimental results demonstrate that COCOA technique not only provides high PSNR values for the watermarked images, but also preserves the watermark visibility under various signal processing operations, especially the watermark removal attack.