A DWT Ordering Scheme for Hiding Data in Images Using Pixel Value Difference

A scheme is proposed to hide data in images based on a prioritised ordering of the content of the host image. The embedding process uses the watermark strength to determine the ordering of the 16 regions resulting from the second level wavelet transform DWT decomposed content of the host image. The DWT decomposed sub-bands of the cover image were analysed, transformed using the Pixel Value Difference (PVD), and then ranked in terms of their ability to withstand changes that do not imperil the visual quality (PSNR) of the watermarked image depending on which an N×N-sized watermark stream is hidden in the 8 highest ranked sub-bands. Using the proposal, a 256×256 Lena image had the capacity to accommodate up to 96800 bits of a watermark logo while still maintaining an appreciable visual quality manifested by a PSNR value of 33.66 dB.