A Digital Image Watermark Algorithm Based on DC Coefficients Quantization

Digital watermark technology is an efficient way to copyright protection. First, DCT coefficients characteristics were analyzed. Then, a new watermark technique quantization was proposed. According to watermark information, DC coefficients of each 8times8 block were modulated in DCT matrix. And an adaptive method was given to obtain quantization distance. The experiments show it does well in transparency and robustness. It can resist against JPEG compression, cut and common image attacks efficiently