Abstract: Enhancement is the modification of image to better visualisation to the viewer. It is a technique to manipulate pixel value to produce an image with optimum contrast. The image used in medical, satellite and edge detection is not of a standard quality so to increase visual appearance and reduced noise enhancement of image is used. Although enhancement techniques differ according to application but they are broadly classified as two type: Spatial domain and Frequency domain. In spatial domain the image is modified i.e. pixel value of image & in frequency domain the frequency of image is modified. Here we will try to provide some image enhancement techniques in spatial as well as frequency domain and use some of the parameter to measure different technique shortcoming.
Keywords: Image enhancement, Histogram Equalization, Local Enhancement, Retinex, Homomorphic filtering.