ABSTRACT
Image enhancement is the process of improving the quality of an image as observed by a human. Image enhancement can be done by processing in spatial domain or in frequency domain. In frequency domain, first the image is converted into frequency domain and then an appropriate enhancement technique is applied. In order to convert an image into frequency domain, a transform such as the Fourier transform, discrete cosine transform, Haar transform or Hough transform is applied. After applying a technique, the processed image is converted back to spatial domain. In this chapter, image enhancement in frequency domain is discussed. The frequency domain filtering is categorized as either low pass filtering or high pass filtering. Low pass filtering is similar to smoothing process and high pass filtering is sharpening. This chapter provides the basics of various frequency domain filters and their implementation.
