Improvement of low contrast images in the frequency domain using fuzzy intensification

Abstract

Due to the variety of types of images, there are currently no universal methods that provide a guaranteed result of solving the problem of improving the quality of low-contrast digital images. Medical systems often produce images of insufficient quality for reliable visual analysis. In particular, X-ray images, characterized by low intensity, un-even background, high level of noise, poor contrast and weakly defined boundaries of structures, are particularly difficult to analyze and choose an effective processing meth-od. The paper presents the information possibilities of the method of processing half-tone medical images aimed at improving the contrast and increasing the detail of ob-jects of interest in order to increase the reliability of diagnosis based on them. The pro-posed algorithm is based on a multi-stage processing process, which includes the use of two-dimensional frequency Fourier transformation and the method of fuzzy intensifica-tion in the spatial domain. The use of two-dimensional discrete Fourier transformation changes not the im-age, but the form of its representation, converting the output signal into its components of different frequencies and amplitudes. In this form, it is much easier to carry out filter-ing or amplification of individual components of the signal. Fuzzy set theory has the ability to quantitatively and qualitatively model problems related to uncertainty and imprecision, which are always present in digital images. Their presence is determined both by the features of the physical processes of image forming systems and by the stage of creating a digital image. The application of the proposed method provides improved contrast and increased detailing of objects of interest and affects the reliability of visual analysis. Only the ar-guments of complex Fourier transform coefficients can be corrected. The method of fuzzy intensification is used as a refinement for the second stage of frequency conversion. The effect of frequency conversion parameters on the detail of the resulting image was stud-ied. The results of the algorithm are presented on the example of real X-ray images.