A Statistical Color Image Watermarking Scheme Using Local QPCET and Cauchy–Rayleigh Distribution

Abstract

Based on local quaternion polar complex exponential transform (QPCET) and Cauchy–Rayleigh distribution, we propose a statistical color image watermarking scheme in this paper, which can achieve the trade-off among imperceptibility, robustness and data payload. Our color image watermarking scheme consists of two parts, namely embedding and detecting. In the embedding process, we divide the color host image into non-overlapping blocks and compute the local QPCET of color image blocks and then insert the watermark signal into the robust local QPCET magnitudes through multiplicative approach. In the detecting phase, robust local QPCET magnitudes are firstly modeled by employing the Cauchy–Rayleigh distribution, where the statistical properties of local QPCET magnitudes are captured accurately. Then, genetic algorithm-based maximum likelihood approach is introduced to estimate the statistical parameters of Cauchy–Rayleigh distribution model. And finally a color image watermark detector for multiplicative watermarking is developed using Cauchy–Rayleigh distribution and locally most powerful test. Also, we utilize the Cauchy–Rayleigh statistical model to derive the closed-form expressions for the watermark detector. Experimental results on some standard test images and comparison with well-known existing methods demonstrate the efficacy and superiority of the proposed scheme.