As a main application of information hiding technique to multimedia copyright protection, the digital watermarking technique, which embeds an invisible signal (watermark) to the original multimedia data (image, audio, and video), has been proposed as a viable solution for the copyright protection and authentication of multimedia data in a networked environment since it makes it possible to identify the author, owner, distributor or authorized consumer of multimedia data. So it has drawn extensive attention in recent years and has been widely applied. A new image watermarking scheme is proposed by incorporating the DCT transform and an edge detection technique. Experimental results show that this method is more robust against the common signal processing attacks than the traditional Cox's method.