Abstract: In this research, a grayscale image watermarking scheme is proposed using a Discrete Cosine Transform (DCT) to embed a binary invisible watermark image. The DCT is applied to the entire host image instead of dividing the image into 8×8 non-overlapping blocks as usual in the conventional schemes and then some of the coefficients in the low-frequency DCT band are selected for the watermark embedding process. For obtaining an acceptable trade-off between the robustness and imperceptibility of the watermark, the watermarking strength is controlled by a robustness factor. The value of the robustness factor is not threshold and can be changed by the user based on the required robustness level and the characteristics of the host image. Peak Signal to Noise Ratio (PSNR) and Normalized Correlation (NC) are calculated to evaluate the images quality. The simulations and results demonstrate that the proposed scheme still holds its validity under various attacks such as JPEG compression, low-pass filtering and noise attacks.
Ghazwan Jabbar Ahmed, Adel Jalal Yousif and Fadhil Kadhim Zaidan, 2019. A Digital Image Watermarking Scheme based on Discrete Cosine Transform. Journal of Engineering and Applied Sciences, 14: 5762-5768.