A Blind Quantization Watermarking Scheme for Screen Content Image

With the development of the big data age, information security is becoming more and more important. Screen content image are composed of text, graphics and natural image. They present strong anisotropic features, especially on the text and graphics parts. It is well known that Spread Transform Dither Modulation(STDM) is more robust to re-quantization, such as JPEG compression, than regular Quantization Index Modulation(QIM). In this paper, we propose a novel watermarking scheme for screen content grayscale image in DCT domain. On the basis of STDM, combined with the characteristics of human visual system, we use the texture complexity effect factor on DCT domain to adjust the watermarking process. To evaluate the performance of our proposed scheme, we use the reference image from the SIQAD image database. The 20 reference SCIs were thoughtfully identified from the Internet, and they cover a wide variety of image contents, including texts, graphics, symbols, patterns, and natural images. Experiments show that our method has a good performance in term of robustness and better visual quality.