Games, commercials, TV, classrooms, industries, hospitals, research laboratories, it is truly in all field of human activity that new images appeared recently: the so called “digital images”. Why this name? Because all these images are coming out of digital computers. If computers were first, only able to deal with numbers, then with words, now, they can manipulate much more complex entities, such as pictures. But to enter the computer world, pictures have to be converted into numbers, to be digitised. Each number manipulated by the computer represents the smallest distinct part of an image, a picture element, a “pixel”. As any picture can be transformed in a set of numbers. Manipulating there numbers with the computer, we can modify, at will, a picture (digital special effects in video, image processing of satellite pictures and so on…). Giving sets of numbers to the computer, we can also create completely new images.