Digital image watermarking by Fresnel transform and its robustness

Watermarking is a technique embedding hidden multimedia information imperceptibly, such as images and sounds. Generally original image is transformed and coded watermark data is embedded in the frequency domain watermarking models. In this paper, we propose a new data embedding method using Fresnel transform. A watermark image is Fresnel-transformed and the intensity of transformed pattern is embedded into original image. Our watermarking model has the flexibility in data hiding. It is possible to embed watermark in many different observable planes with various distance parameters of Fresnel transform and all kinds of image models such as shape, letter and photo can be used as watermark data. Using Fresnel transform with various distance parameters, it is possible to get many channels for embedding. So our method can recover the weak point having only one transform plane in DFT and DCT domain methods. The watermarking experiments were conducted to show the validity of the proposed method, and the results show that our method can provide multi frequency domains for embedding watermark and have robustness against filtering and geometric transformation.