Robust Color Image Watermaking Scheme

A robust watermark should be able to withstand most image manipulation such as cropping, additive noise and JPEG compression. It is a well known fact that the watermarking of DC components of discrete Cosine transform (DCT) stand against JPEG compression. We build on this concept by inserting a watermark in the transform domain to further enhance the robustness. In this paper, a method for embedding the chaotic watermark in the DCT transform domain for color images is proposed. The watermark information is embedded in the three colour components of the RGB space. The insertion consists in modifying some blocks for each channel, middle frequency components of the red channel, high frequency components of the green channel and low frequency components of the blue channel. Watermark detection is performed without using the host image, by computing the correlation value between the stego-image and the original watermark in the transform domain. The proposed method yields a good result in terms of the PSNR performance, compared with that using the blue channel. Experimental results demonstrate that the new embedding rule enhances the quality of the watermarked image, and the robustness under various types of common image processing. Keywords—Digital watermarking; Imperceptibility; Robustness; Color space; DCT domain; Chaotic map.