DCT and DWT-based image watermarking by using subsampling

A subsampling based watermarking scheme has been investigated for digital images. The algorithm utilizes the wavelet multiresolutional structure and subsamples the individual subband coefficients in order to embed the watermark information respectively. The extracting procedure reverses the embedding operations without the reference of the original image and provides a better copyright protection scheme. Compared with the similar approach by discrete cosine transform based approach, the wavelet based algorithm apparently preserves superior image quality and robustness under various attacks.