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Saturday, 15 February 2014

Computer Graphics Notes Lab 1

What is computer graphics?

What is computer graphics?
The computer is an information processing machine. It is a tool for storing, manipulating and correlating data. The computer graphics is one of the most effective and commonly used ways to communicate the processed information to the user, Computer graphics is the field of computer science in which we are interested in generating objects and images such as pictures, charts, graphs and diagrams using pixels. It started with elementary programs like point, line and circle generation. But with the development of interactive input and output devices it is possible virtually to design anything on the computer system. Multimedia, CAD and CAM have all been possible because of computer graphics.

How pictures or graphics objects are presented in computer graphics?

In computer graphics pictures or graphics objects are presented as a 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 color 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 an infinite number of points. For example, if we want to display point Pı whose coordinates are (4.2, 3.8) and point P2 whose coordinates are (4.8, 3.1) then Pı and P2 are represented by only one pixel (4, 3) as shown in the figure. In general, a point is represented by the integer part of x and integer part of y, i.e., pixel (int(x), int(y)).

The special procedures determine which pixel will provide 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 adding effects such as hidden surface removal, shading or transparency to the picture before final presentation.

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