The problem of affine transform attacks refers to many watermarking algorithms. A slight change in the geometry of watermarked image can disable the decoding of embedded information; therefore the advanced watermarking methods should be robust against the above-mentioned procedures. This paper contains a description of the algorithm consisting of two complementary methods of image watermarking. The watermark is encoded in the luminance and chrominance components in the spatial and frequency domains. The decoding process takes place in the two-dimensional Cepstrum and the discrete cosine transform. The algorithm makes the watermarked image robust against the following affine attacks: scaling shearing and translation. Also the following image distortion processes like JPEG lossy compression, adding noise to the watermarked image, median filtering and majority cropping do not cause any loss of hidden information.

The protection of copyrights of digital images authors is one of the most important tasks set before watermarking. What is especially important is to ensure the high robustness of a watermarked images against attacks, preventing the reading of additional information about the author. In addition, the used processing of the original image must be absolutely invisible. The presented algorithm embeds information in a parallel way-independently of the luminance and chrominance matrices in the spatial and frequency domains. The main factor motivating the use of a parallel watermark embedding via the proposed way was the mutual complementing of robustness, offered by processing in spatial and frequency domains. Additional information is recovered in a 2D cepstrum domain and in coefficients of the cosine transform. The article shows a description of a mathematical model, tests of invisibility, effectiveness and the robustness of the method were carried out. The robustness of the algorithm was shown against the following attacks: JPEG and JPEG2000 lossy compression, noise, median filtering, Low-Pass and High-Pass filtering, desynchronization, simple and inverse D/A conversion, majority cropping, photomontage and affine transforms-rotation, scaling, shearing, translation.

Watermarking is a dynamically developing method of copyright protection used for media (sounds, images, films, or 3D objects) that employs signal processing in order to hide additional, invisible information about the owner or author. However, studies until now have not widely considered the problem of attempting to blind removal of hidden data in a manner that allows the watermarked signal to be returned to the original signal. Current considerations of authors of leading articles in the watemarking field focus on the robustness of the method -security system against intentional attacks of removal of the additional information, without taking into account the aspect of simultaneous degradation of the quality and form of the watermarked picture. As has been shown in the article, it is possible to design a perfect filter (same as reversible operations) that allows the removal of additional information from the watermarked picture in a way that makes it possible to return to the form of the host image. This paper describes an ideal filter used for removal of additional, invisible information in forms of an eliminating function and a signal masking function. Their effectiveness has been demonstrated for practical implementations of this type of eliminating and masking filters for watermarking methods in the cepstrum domain.

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