Images can be processed by optical, photographic, and electronic means, but image processing using digital computers is the most common method because digital methods are fast, flexible, and precise. In the future, Electro-optical and some analog image-processing methods may be commonly used. This article focuses on the use of digital computer methods.
In a typical digital image processing system, the source of the image is usually visible light reflected from or transmitted through various objects in a scene. Optics gathers and focuses this light into a sensor that puts an electronic signal to the received light. Images can also be formed using other sources of radiation such as infrared or ultraviolet light, X-rays, radar, or sonar. Images can be synthesized from spatial data by other means, including scanning and computer-aided tomography. .
The sensor signal is "digitized"--converted to an array of numerical values, each value representing the light intensity of a small area of the scene. The digitized values are called picture elements, or "pixels," and are stored in computer memory as a digital image. The limited range and number of pixels means that the digital image is only an approximate of the light intensity from the scene.
A computer to achieve the desired result processes the digital image. Often special purpose image-processing computers are used to increase the speed of the processing operations. The sequence of processing operations is called an image processing. The processed result could be displayed, be recorded, control a manufacturing operation, provide measurements on the image, or be sent over a communication channel for remote.
Some of the equipment used in image processing is also used in computer graphics and scientific visualization. Graphics and image processing are often combined in the preparation of printed material. .
IMAGE ENHANCEMENT AND RESTORATION.
Image enhancement improves the quality of images, perhaps for human viewing.