Basic Gray Level Image Processing

Publisher Summary This chapter describes the basic tools for digital image processing. The basic tool that is used in designing point operations on digital images is the image histogram. The histogram of the digital image is a plot or graph of the frequency of occurrence of each gray level. Hence, a histogram is a one-dimensional function with domain and possible range extending from 0 to the number of pixels in the image. One of the most important nonlinear point operations is histogram equalization, also called histogram flattening. The idea behind it extends that of FSHS: not only should an image fill the available grayscale range but also it should be uniformly distributed over that range. Hence an idealized goal is a flat histogram. Although care must be taken in applying a powerful nonlinear transformation that actually changes the shape of the image histogram, rather than just stretching it, there are good mathematical reasons for regarding a flat histogram as a desirable goal. In a certain sense, an image with a perfectly flat histogram contains the largest possible amount of information or complexity.