Estimating stability of structural and brightness properties in image digital processing

The article considers determining the stability assessment of the structural and brightness properties of raster images. The stability assessment refers to the ability of preserving the image properties due to the original image processing by filtering. Halftone versions of the full-color images presented in the RGB color space are accepted as original images. The grayscale images are filtered using the Gaussian, Wiener, and median filtration algorithms. The next step is to use one of the variants of the SSIM algorithm to obtain the structural similarity index between the control halftone image and the filtered image. In order to create a relative and dimensionless metric there has been calculated the area of the polygon $S$ set by the values of the similarity indices relative to the control grayscale image, and the area of the rectangle $Sp$ that contains the area of the polygon S. Images from the international image database TID2008 (image database 2008), TID2013 (image database 2013) were taken as test bitmaps. The official coats of arms of the Russian Federation entities – territories, regions, republics, etc. - were also considered. The resulting stability score is determined either as the geometric mean of the four calculated values, or as their arithmetic mean. The results of testing the groups of bitmap images that are united by a common theme or purpose are presented. From each group of images, the maximum and minimum values of the estimates of the image stability to structural and brightness changes are determined in accordance with the developed heuristic algorithm. The results obtained can be used for comparative evaluation of competing images in order to select the most resistant to structural and brightness changes.