The digital watermarking method by using both patchwork and DCT

The technique of the digital watermark is proposed as a way of solving the copyright protection problem for digital contents, which accompanies the development of computer networks. There is a way that a watermark is embedded in the frequency domain. This method can endure the compression of the image but is weak in cropping of the image. Therefore, the purpose of the paper is to propose a digital watermarking method, so that the watermark can be detected even if an image is cropped too.