Abstract
Just noticeable distortion (JND) is widely employed to describe the perception redundancy in the quantization-based watermarking framework. However, the existing JND models are generally constructed to treat every region of the photograph with an equal focus level, whereas the defocus effect has never been considered. In this paper, the defocus feature, which can portray the aesthetic emphasis in the photograph, is provided to improve the perceptual JND model. Firstly, two indicators which consider the block energy in the defocus measurement (DM) are proposed. Then, the defocus feature map (DFM) is obtained by integrating the influence of the circumambient blocks, and it is applied to the proposed JND contrast masking (CM) processing. In this way, a new blind photograph watermarking method, with emphasis on defocus-JND estimation combined with the proposed CM, is presented. Simulations show that the proposed JND is more suitable for watermarking framework than some exiting JND models, and the proposed watermarking scheme with the improved defocus-based JND model has superior robustness compared with some watermarking schemes.
Highlights
In recent years, there has been a surge of interest in taking photos using a digital camera
A blind watermarking method is proposed to protect aesthetic photographs based on a new Just noticeable distortion (JND) model with defocus analysis
We propose a new defocusbased JND model which can reflect the characteristic of human visual system (HVS) that the eyes will take more time to gaze at focus areas
Summary
There has been a surge of interest in taking photos using a digital camera. The existing JND models cannot satisfy the balance between invisibility and robustness better under this requirement (2) We propose a new defocus measurement and apply it into CM. In this measurement, as the influence of defocus differs in blocks with different energies, two types of blocks called strongly and weakly textured blocks are distinguished by some representative alternating current (AC) coefficients in DCT domain. The experimental results show that the defocus measurement can take its role effectively (3) The proposed robust defocus-based JND model is implemented to estimate an optimum quantization step adaptively for the quantization-based watermarking framework.
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