Public watermarking algorithm based on the polarity of DCT coefficients

This paper presents a novel public watermarking algorithm based on the AC coefficients distribution properties of an image's DCT transform. This method uses the signs of the DCT coefficients to represent the bit 1 and 0 respectively. Furthermore, the parameters of this scheme can be calculated since we analyze the round-off errors caused by storing a watermarked image. The experiment results show that the algorithm is effective and robust to common image processing operations, such as JPEG lossy compression, Gaussian noise attack, cropping, lowpass filter and histogram equalization.