Abstract:

In order to improve the performance of color image digital watermark and take into account the correlation between three color channels of color image, a QR matrix decomposition watermark embedding algorithm based on discrete cosine transform(DCT) and discrete quaternion Fourier transform(DQFT) was proposed, which integrated the good robustness of watermark algorithm based on transform domain and could embed watermark information by processing the three channels of color image as a whole. Firstly, the three RGB channels of the color image were discrete cosine transformed respectively, and the transformed three 1/4 medium and low frequency components were selected as the three imaginary parts of the quaternion matrix to construct a pure quaternion matrix Q. The Q was discrete quaternion Fourier transformed, and the transformed real part was selected for 4×4 blocks, the data of which was QR decomposed and the watermark information was embedded. Experimental results show that the proposed watermarking algorithm is robust to noise attacks, JPEG compression, median filtering and other attacks.

Key words: DCT, quaternion, DQFT, QR decomposition, blind watermarking