Abstract
In this paper we present an overview of methods for contrast enhancement of grayscale images. These methods are important for better visualization of images in various fields (biomedical imaging, space imaging, surveillance imaging...). First we present the time-domain methods and than the frequency-domain methods. All methods were implemented and applied to artificial and real images. Their ability to correct the contrast of degraded images is illustrated and correction times are given. Finally, we discuss the positive and negative sides of the individual methods.