A discrete trinion Fourier transform (DTFT) is proposed and computation of the DTFT is derived from the discrete Fourier transform. A block-based color image watermarking scheme is designed based on the proposed DTFT. The watermark bits are embedded by modifying the DTFT coefficients of each block by means of the quantization index modulation method. Finally, assessment of this watermarking approach is performed in terms of watermark capacity, invisibility, and robustness. A comparison with a quaternion discrete Fourier transform is also provided. Experimental results show that the proposed method is not only more robust in most standard attack situations, but also has superior time efficiency.
This paper presents a novel robust color image zero-watermarking scheme based on SVD and visual cryptography. We firstly generate the image feature from the SVD of the image blocks, and then employ the visual secret sharing scheme to construct ownership share from the watermark and the image feature. The low frequency component of one level discrete wavelet transform of the color image is partitioned into blocks. Then we propose to use the feature generated from the first singular value of the blocks to construct the master share. When ownership debate occurs, the ownership share is used to extract the watermark. Experimental results show the better performance of the proposed watermarking system in terms of robustness to various attacks, including noise, filtering, JPEG compression and so on, than other visual cryptography based color image watermarking algorithm.