Lilisand and Kiefer (1994) explained digital image processing involves the manipulation of digital image with the aid of computer which is an extremely board subject, and it often involves procedures which can be mathematically complex.

The central idea behind digital image processing is quite simple. The digital image is fed into a computer one pixel at a time. The computer is programmed to insert these data into an equation, or series of equation, and then store the results of the computation for each pixel. These results from a new digital image can be displayed or recorded in pictorial format or may addition programs further manipulate it. The possible from of digital image manipulation is literally infinite. However, virtually all these procedures can be categorized into one (or more) of the following five broad types of computer-assisted operations:

• Input data

• Image rectification and restoration

• Image enhancement

• Image classification

• Data merging and GIS integration