Brightness Preserving Generalized Histogram Equalization with High Contrast Enhancement Ability

摘要

Histogram equalization (HE) is the one of the simplestand most effective methods for contrast enhancement. It can automaticallydefine the gray-level mapping function based on the distribution of graylevelincluded in the image. However, since HE does not use a spatialfeature included in the input image, HE fails to produce satisfactory resultsfor broad range of low-contrast images. The differential gray-level histogram(DH), which is contained edge information of the input image, wasdefined and the differential gray-level histogram equalization (DHE) hasbeen proposed. The DHE shows better enhancement results compared toHE for many kinds of images. In this paper, we propose a generalized histogramequalization (GHE) including HE and DHE. In GHE, the histogramis created using the power of the differential gray-level, which includes thespatial features of the image. In HE, the mean brightness of the enhancementimage cannot be controlled. On the other hand, GHE can control themean brightness of the enhancement image by changing the power, thus,the mean brightness of the input image can be perfectly preserved whilemaintaining good contrast enhancement.