A robust DCT-2DLDA watermark for color images

A blind watermarking algorithm is proposed, which is based on the Discrete Cosine Transform (DCT) method. It uses Two-Dimensional Linear Discriminant Analysis (2DLDA) watermark scheme for copyright protection. During the embedding process, the color image is converted into the YIQ color space. The quadrature chrominance component is transformed into frequency domain and it uses DCT method. Then, two binary watermarks for reference and logo are added to particular bits of the AC coefficients. During the extraction process, the logo watermark is extracted using matrix-based 2DLDA based on DCT method. By embedding the training data and using a matrix-based 2DLDA scheme, we do not need all the embedded information. The numbers of training samples for each class are small; the training covariance matrices are directly computed from 2D image samples by using 2DLDA. This ensures the efficient and the robustness of watermark extraction. Experimental results demonstrate that the differences between the watermarked image and the original image are indistinguishable. The proposed method is effectively resist common image processing attacks.