Image contrast enhancement is important in medical applications. This is due to the fact that the visual study of medical images is important for the diagnosis of many diseases. To improve the contrast of medical images, various contrast enhancement methods are used, such as histogram alignment, histogram modification methods, gamma correction, etc. The article studies methods of increasing the contrast of graphic images, in particular methods of improving the quality of X-ray images. The research was carried out in several stages. Attempts have been made to increase the contrast of several dozen X-ray images in order to select the best image brightness using brightness conversion methods in the MATLAB system. During the experiments, the need for sequential implementation of several methods to increase the contrast of images was determined. To obtain the best result before performing gamma correction, it is proposed to use the method of equalizing the histogram of the X-ray image. The possibilities of the method of image histogram alignment are considered. As a result of the comparison, an improved version of this algorithm is presented. The use of an adaptive histogram alignment algorithm with limited contrast gives a visual effect of improving the contrast of X-ray images. To objectively quantify the results of the transformation, the niqe and brisque evaluation functions are used, which do not use reference images.