Improving the robustness of DCT-based image watermarking against JPEG compression

A DCT-based image watermarking technique is proposed in this article. To improve the robustness of watermark against JPEG compression, the most recently proposed techniques embed watermark into the low-frequency components of the image. However, these components hold significant information of the image. Directly replacing the low-frequency components with watermark may introduce undesirable degradation to image quality. To preserve acceptable visual quality for watermarked images, we propose a watermarking technique that adjusts the DCT low-frequency coefficients by the concept of mathematical remainder. Simulation results demonstrate that the embedded watermarks can be almost fully extracted from the JPEG-compressed images with very high compression ratios.