A time-frequency based perceptual and robust watermarking scheme

In the past decade, watermarking has become an important tool in copyright protection applications. In this paper, we introduce a new watermarking scheme in the joint time-frequency domain. Wigner distribution is used to transform an image into the spatial-spectral domain. The proposed method selects the time-frequency cells to be watermarked based on the particular image´s energy distribution in the joint domain. This approach ensures the imperceptibility of the embedded watermark. It is shown that embedding in the time-frequency domain is equivalent to a nonlinear embedding function in the spatial domain. A corresponding watermark detection algorithm is also introduced. The performance of the proposed watermarking algorithm under possible attacks, such as noise, re-sampling, rotation, filtering, and JPEG compression is illustrated.