Enhancing the robustness of image watermarking against cropping attacks with dual watermarks

In this study, a QR-based digital watermarking scheme that can use color images is proposed. The main purpose of this method is to enhance robustness against cropping attacks. To achieve this aim, each bit of the robust watermark has four copies, which are hidden in different image blocks. The embedding rule is designed based on the sinusoidal function, and the wavelength of the sinusoidal function controls the trade-off between imperceptibility and robustness. The four copies of the watermark bit may be inconsistent if the watermarked image undergoes cropping attacks. Therefore, after the four copies of the watermark bit are extracted, the actual value of the watermark bit is judged based on the result of the tampering detection. Experimental results indicate that improving robustness with the help of tampering detection results effectively assists in watermark extraction. In addition, the method is superior to other methods in terms of invisibility, robustness, and embedding payload.