A. Phadikar, S.P. Maity (India), and M.K. Mandal (Canada)
Passive Data Hiding, Quality Access Control, QIM, Dither Modulation.
This paper proposes a Discrete Cosine Transfer (DCT) domain data-hiding scheme for quality access control of images. Host image is divided into non-overlapping blocks of pixels, and blocks are grouped into various categories based on variance values. A binary watermark image (external information) is permutated using the sequence of numbers generated by a secret key. Each encoded watermark bit is then embedded in a block by modulating the AC coefficients using dither modulation (DM) but without complete self-noise suppression. It is well known that due to insertion of external information, there will be degradation in visual quality of the host image (cover). The degree of deterioration depends on the amount of external data insertion as well as step size used for DM. If this insertion process is reverted, better quality of images can be accessed. To achieve that goal, watermark bits are detected using minimum distance decoder and the remaining self-noise due to information embedding is suppressed to provide better quality of image. The simulation results have shown the validity of this claim.
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