A method of embedding a color digital watermark into a gray-level image is proposed.By still image compression coding technique

the color digital watermark is encoded into a series of binary ID numbers for watermarking.The algorithm can extract the watermark without the original image because the embedding process is based on the relationship between the discrete cosine transform (DCT) coefficients of the original image.Experimental results show that the proposed technique is robust against some image processing operations and joint photographic experts group (JPEG) lossy compression.