A digital image watermarking algorithm based on the combination of the DWT and the DCT

An algorithm for the gray-scale image digital watermarking was proposed by combination of the DWT and DCT transformation.First,scrambling and chaos the binary watermark image and then modulate a sequence of watermark image into a sequence of positive and negative.In the watermark embedding process,we perform wavelet transform to the image and extract the low-frequency coefficient matrix of it,then the low-frequency coefficient matrix is divided into 4×4 sub-block,with each sub-block being transformed with DCT,and the positive and negative methods has been used to quantify the embedded watermark.The experimental results show that the algorithm has a good resistance and better robustness for attacking the JPEG compression,plus noise,shear,filtering and so on.