Robust Reversible Watermarking Using Polar Harmonic Transform on RGB Image

As access to digital information continues to expand, the protection of digital content has become increasingly critical. This research addresses the pressing challenges of data security by proposing a novel watermarking scheme based on Polar Harmonic Transform (PHT) specifically designed for RGB images. This approach significantly enhances both imperceptibility and robustness in RGB images. Unlike many existing watermarking techniques that primarily focus on grayscale images, this study uniquely applies the method developed by Tang et al. to RGB images, broadening its applicability. To evaluate the proposed scheme, two experimental approaches are employed: one involves watermark embedding in a single layer of RGB images, while the other entails embedding across all layers. By integrating advanced techniques such as PHT, Direct Current Quantization Index Modulation (DC-QIM), and Phase Encoded Encoding with Hamming Space (PEE-HS), the method demonstrates substantial improvements in imperceptibility and data recovery capabilities. Experimental results indicate that when the watermark is embedded in the green layer of RGB images, a peak signal-to-noise ratio (PSNR) of 44.96 dB is achieved, along with a bit error rate (BER) of 0. Robustness tests conducted against various attacks, including JPEG compression with quality factors greater than or equal to 30, Gaussian filtering with kernel sizes up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$7\times 7$</tex>, and Speckle noise with variances less than or equal to 0.027, further confirm the effectiveness of the proposed watermarking scheme in resisting different types of attacks.