Raster and Random Scan Display Technologies
For display or printing graphics objects, various technologies have been invented. Research and development is still on for getting refined and more advanced display technologies for achieving as much realism as possible in graphics display. Early graphics devices were line-oriented. This means the primitive operations were line drawing. For example, a plotter was based on sketching the figure through a pen using line segments approximating the graphics object. For complex objects, thousands of line segments were used to plot the object.
Such devices were called vector displays or random scan displays. In the present time raster graphics is a standard technology commonly used in most of the graphics devices. Raster graphics uses a raster which is a 2-dimensional grid of pixels (picture elements). Each pixel may be addressed and illuminated independently, just as in a graph paper, we are able to address every cell independently. Therefore the primitive operation is to draw a point which means to assign a color to a pixel. Everything else is built upon that. There are a variety of hardcopy and display devices based on raster graphics technology. The inkjet and laser printers are examples of hardcopy devices whereas CRT (cathode ray tube) and LCD (liquid crystal display) are well known examples of display devices based on raster graphics.