Geometrically robust image watermarking via pseudo-Zernike moments

In image watermarking, the watermark robustness to geometric transformations is still an open problem. Using invariant image features to carry the watermark is an effective approach to addressing this problem. In this paper a geometrically robust image watermarking scheme using pseudo-Zernike moments is proposed. Some selected pseudo-Zernike moments of an image are computed, and their magnitudes are quantized by dither modulation to embed an array of bits. The watermarked image is obtained via reconstruction from the modified moments and those left intact. In watermark extraction, the embedded bits are estimated from the invariant magnitudes of the pseudo-Zernike moments using a minimum distance decoder. Simulation results show that the hidden message can be decoded at low error rates, robust against image rotation, scaling, flipping, and as well, a variety of other processes such as lossy compression.