Extended DCT Domain for Improving the Quality of Watermarked Image

In this paper, we propose a novel and robust image watermarking based on the extended DCT domain, called q-DCT domain. By using the extended DCT domain, we can control the quality of the watermarked image. In our proposed scheme, we embed the watermark in the low-frequency of q-DCT domain in order to achieve the robustness of watermark. We also choose in our method a watermarking technique in the category of quantization index modulation (QIM) due to its good robustness and blindness. In our proposed method, the trade off of robustness and quality can be controlled by the parameters of QIM and the parameter q of logarithm transform.