A robust blind color image watermarking in quaternion Fourier transform domain

Highlights? To embed the digital watermark in quaternion Fourier transform domain, which improves the robustness against color attacks. ? To correct the watermarked image by LS-SVM classification, which improve the robustness against geometrical distortions. ? To modify the symmetric quaternion Fourier transform coefficients, which improve the watermark imperceptibility. Most of the existing color image watermarking schemes were designed to mark the image luminance component only, which have some disadvantages: (i) they are sensitive to color attacks because of ignoring the correlation between different color channels, (ii) they are always not robust to geometric distortions for neglecting the watermark desynchronization. It is a challenging work to design a robust color image watermarking scheme. Based on quaternion Fourier transform and least squares support vector machine (LS-SVM), we propose a robust blind color image watermarking in quaternion Fourier transform domain, which has good visual quality. Firstly, the original color image is divided into color image blocks. Then, the fast quaternion Fourier transform is performed on the color image block. Finally, the digital watermark is embedded into original color image by adaptively modulating the real quaternion Fourier transform coefficients of color image block. For watermark decoding, the LS-SVM correction with pseudo-Zernike moments is utilized. Experimental results show that the proposed color image watermarking is not only robust against common image processing operations such as filtering, JPEG compression, histogram equalization, and image blurring, but also robust against the geometrical distortions.