A Novel Robust Watermarking Algorithm Based on DWT and DCT

In this paper, a novel robust watermarking algorithm is presented in mixed transform domain. The original host image is first decomposed into four sub-bands by Discrete Wavelet Transform (DWT). Then approximate coefficients are relocated by Arnold transform to create a noise-like version and divided into non-overlapping 8 × 8 blocks. Each block is Zig-zag scanned and sorted in descending order before the DCT transform to obtain high robustness and transparency. A watermarking sequence encrypted by Arnold transformation with secret keys is afterwards embedded into the DCT transform coefficients according to JND (Just Noticeable Difference) model. The watermark is extracted without the original image. Experimental results indicate that the proposed strategy has a good robustness against common attacks, such as noise, filtering, JPEG compression.