Reversible watermarking method based on adaptive thresholding and companding technique

Abstract

Embedding and extraction of secret information as well as the restoration of the original un-watermarked image are highly desirable in sensitive applications such as military, medical, and law enforcement imaging. This paper presents a novel reversible watermarking approach for digital images using integer-to-integer wavelet transform, companding technique, and adaptive thresholding, enabling it to embed and recover the secret information as well as restore the image to its pristine state. The proposed method takes advantage of block-based watermarking and iterative optimization of threshold for companding which avoids histogram pre- and postprocessing. Consequently, it reduces the associated overhead usually required in most of the reversible watermarking techniques. As a result, it generates less distortion between the watermarked and the original image. Experimental results on regular as well as medical images show that the proposed method outperforms the existing reversible watermarking approaches reported in the literature.

Keywords:

• reversible watermarking
• data authentication
• companding technique
• integer wavelet transform
• adaptive thresholding
• data hiding

2010 AMS Subject Classifications :

• 68U10
• 91G20
• 55S36
• 65T60
• 94A62

Acknowledgements

Authors are very grateful to Ghulam Ishaq Khan Institute of Engineering Sciences and Technology (GIK) and Pakistan Institute of Engineering and Applied Sciences (PIEAS) for providing resources and environment for carrying out this research. Image databases were provided by AGA Medical University Karachi and Ackron University, Ohio, USA. This work was supported by Quaid-e-Awam University of Engineering, Science and Technology (QUEST), Nawabshah, Sindh under Inland Scholarship Programme.