Darko Agić

Discrete Fourier transform–based watermarking method with an optimal implementation radius

In this paper, we evaluate the degradation of an image due to the implementation of a watermark in the frequency domain of the image. As a result, a watermarking method, which minimizes the impact of the watermark implementation on the overall quality of an image, is developed. The watermark is embedded in magnitudes of the Fourier transform. A peak signal-to-noise ratio is used to evaluate quality degradation. The obtained results were used to develop a watermarking strategy that chooses the optimal radius of the implementation to minimize quality degradation. The robustness of the proposed method was evaluated on the dataset of 1000 images. Detection rates and receiver operating characteristic performance showed considerable robustness against the print-scan process, print-cam process, amplitude modulated, halftoning, and attacks from the StirMark benchmark software.

Reduction rate strategies by programmed NIR dual image reproduction process

Autotypic reproduction used in printing procedures as opposed to standard subtractive system used in color photography, except CMY system components, usually adopts black carbon ink within practiced screening system, commonly denoted as four-color printing. Black color incorporated as black printer or K-channel replenish various features including undercolor adjustments and achromatic interchange, which is crucial for achieving secondary, only near- infrared, NIR detectable image

Developing a custom colour target for artwork imaging

Abstract When characterising digital camera for capturing art paintings, the standard targets are often used, resulting in unacceptable differences in reproducing some special colours, so additional time must be spent for visual editing and colour adjusting in various software applications. To avoid the need for excessive colour editing, and to improve workflow efficiency and colour accuracy, the special colour reference target for digital camera characterisation was developed, applied and tested in these research. The object of digitalisation was paintings made with gouache paint, so two custom gouache reference targets with different numbers of colour samples (named CGRT24 and CGRT96) were created for digital camera colour characterisation. The main criteria for construction of targets were defined, as the optimal studio conditions for digital image capture of art paintings. By analysing the results gained with profiles testing, it was established that the errors in colour reproduction, which appear when using the standard targets (GretagMacbeth ColorChecker and ColorChecker DC) was decreased when using the developed CGRT targets for digital camera characterisation. Also, it was found out that the larger number of colour samples on target does not guarantee the more accurate camera profile. The results show that the colorimetric properties of colour samples are more important than the number of samples and proves that there is a benefit of developing the custom target tailored to the specific need.

The Model of Degradation of Color Values in a Reproduction Process

This paper deals with the problem of the degradation of color information that happens when color image is converted from one medium to another. The purpose of experiment was to determine the behaviour between two closely related colors when transferred on paper and then digitalized back using scanner. The aim of research was to examine the possibility of information hiding by means of modification of RGB channels of a digital color image.

Case study: Digital offset printing- resolution and color reproduction

In this paper, the influence of resolution on the color quality reproduction in digital offset printing were investigated. In our experiment special test charts were printed with different resolutions and compared. The results show that high resolution improve image contrast but not the color reproduction.