In computer graphics, pictures or graphics objects are presented as o collection of discrete picture elements called pixels. The pixel is the smallest addressable screen element. It is the smallest piece of the display screen which we can control. The control is achieved by setting the intensity and colour of the pixel which compose the screen.

Each pixel on the graphics display does not represent mathematical point. Rather, it represents a region which theoretically can contain a infinite number of points.
The special procedures determine which pixel will the best approximation to the desired picture or graphics object.
The process of determining the appropriate pixels for representing picture or graphics object is known as rasterization, and the process of representing continuous picture or graphics object as a collection of discrete pixels is called scan conversion.
The computer graphics allows rotation, translation, scaling and performing various projections on the picture before displaying it. It also allows to add effects such as hidden surface removal, shading or transparency to the picture before final representation. It provides user the control to modify contents, structure and appearance of pictures or graphics objects using input devices such as a keyboard, mouse, or touch-sensitive panel on the screen. There is a close relationship between the input devices and display devices.
Therefore, graphics devices includes both input devices and display devices.

The computer graphics is a collection, combination and representation of real or imaginary objects from their computer-based models. Thus we can say that computer graphics concerns the pictorial synthesis of real or imaginary objects.
However,the related field image processing or sometimes called picture analysis concerns the analysis of scenes, or the reconstruction of models of 2D or 3D objects from their picture. This is exactly the reverse process.

The image processing can be classified as:
· Image enhancement
· Pattern detection and recognition
· Scene analysis and computer vision

The image enhancement deals with the improvement in the image quality by eliminating noise or increasing image contrast.

Pattern detection and recognition deal with the detection and clarification of standard patterns and finding deviations from these patterns. The optical character recognition (OCR) technology is an practical example of pattern detection and recognition.

Scene analysis and computer vision deals with the

recognition and reconstruction of 3D model of scene from several 2D images.

The above three fields of image processing proved their importance in many area such as finger print detection and recognition, modeling of buildings, ships, automobiles etc., and so on.
We have discussed the two fields : computer graphics and image processing of computer processing of pictures. In the initial stages they were quite separate disciplines. But now a days they use some common features, and overlap between them is growing. They both uses raster displays.

Today, a high quality graphics displays of personal computer provide one of the most natural means of communicating with a computer

It provides tools for producing pictures not only of concrete, ‘real-world’ objects but also of abstract, synthetic objects, such as mathematical surfaces in 4D and of data that have no inherent geometry, such as survey results.
It has an ability to show moving pictures, and thus it is possible to produce animations with interactive graphics.
With interactive graphics use can also control the animation by adjusting the speed, the portion of the total scene in view, the geometric relationship of the objects in the scene to one another, the amount of detail shown and so on.
The interactive graphics provides tool called motion dynamics. with this tool user can move and tumble objects with respect to a stationary observer, or he can make objects stationary and the viewer moving around them. A typical example is walk thorough made by builder to show flat interior and building surroundings. In many case it is also possible to move both objects and view