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Mathematical Problems in Engineering
Volume 2012, Article ID 635738, 14 pages
Research Article

Haar-Wavelet-Based Just Noticeable Distortion Model for Transparent Watermark

1Department of Electrical Engineering, National Central University, Chungli City 320-01, Taiwan
2Department of Computer Science and Information Engineering, National United University, Miaoli 360-03, Taiwan
3Department of Electronics Engineering, Chung Hua University, Hsinchu City 300-12, Taiwan

Received 3 June 2011; Accepted 5 July 2011

Academic Editor: Carlo Cattani

Copyright © 2012 Lu-Ting Ko et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Watermark transparency is required mainly for copyright protection. Based on the characteristics of human visual system, the just noticeable distortion (JND) can be used to verify the transparency requirement. More specifically, any watermarks whose intensities are less than the JND values of an image can be added without degrading the visual quality. It takes extensive experimentations for an appropriate JND model. Motivated by the texture masking effect and the spatial masking effect, which are key factors of JND, Chou and Li (1995) proposed the well-known full-band JND model for the transparent watermark applications. In this paper, we propose a novel JND model based on discrete wavelet transform. Experimental results show that the performance of the proposed JND model is comparable to that of the full-band JND model. However, it has the advantage of saving a lot of computation time; the speed is about 6 times faster than that of the full-band JND model.