The field of digital image processing refers to processing digital images by means of digital computer. Digital image is composed of a finite number of elements, each of which has a particular location and value. These elements are called picture elements, image elements, pels and pixels. Pixel is the term used most widely to denote the elements of digitalimage.
An image is a two-dimensional function that represents a measure of some characteristic such as brightness or color of a viewed scene. An image is a projection of a 3- D scene into a 2D projection plane.
An image may be defined as a two-dimensional function f(x,y), where x and y are spatial (plane) coordinates, and the amplitude to f(t) any pair of coordinates (x,y) is called the intensity of the image at that point. The term gray level is used often to refer to the intensity of monochrome images. Color images are formed by a combination of individual 2-D images. For example, the RGB color system, a color image consists of three (red, green and blue) individual component images. For this reason, many of the techniques developed for monochrome images can be extended to color images by processing the three component images individually
An image may be continuous with respect to the x- and y- coordinates and also in amplitude. Converting such an image to digital form requires that the coordinates, as well as the amplitude, be digitized