Abstract
Thanks to the exceptionally good properties, such as ergodicity, pseudo-randomness, sensitivity to initial conditions and control parameters, chaotic maps have been widely studied and applied to devise image shuffling, encryption and watermarking schemes. In this paper, the chaotic nature of affine transformation is studied. The affine transformation is then utilized to generate pseudo-random number sequence and applied to shuffle the host image during the preprocessing of watermarking. The watermarking is performed in the spatial domain, where the watermark bits are also encrypted by the skew tent map and then embedded in the shuffled host image. The proposed shuffling scheme yields good scrambling effects compared with the conventional scheme. The watermarked images are robust against various attacks, such as cropping, JPEG compression, noise, etc.