Ghazwan  Jabbar Ahmed, Fadhil  Kadhim Zaidan, Adel Jalal  Yousif, 
    A Digital Image Watermarking Scheme based on Discrete Cosine Transform,
    Journal of Engineering and Applied Sciences,
    Volume 14,Issue 16,
    2019,
    Pages 5762-5768,
    ISSN 1816-949x,
    jeasci.2019.5762.5768,
    (https://makhillpublications.co/view-article.php?doi=jeasci.2019.5762.5768)
    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.
    Keywords: watermarking techniques;copyright protection;digital watermarking;Discrete cosine transform;JPEG compression;normalized correlation;robustness and imperceptibility