Computer Graphics

views updated May 21 2018


Computer graphics are found in almost every industry; individuals in all demographic, geographic, racial, political, and religious groups benefit from them. When picking up a magazine or newspaper, watching television, going to the movies, or taking a drive down the street, images produced by computer graphics are seen.

Computer graphics are used because they add color, excitement, and visual stimulation to media. They are aesthetically appealing and informative. Newspapers, magazines, brochures and reports, billboards, posters, art prints, greeting cards, and postcards incorporate digital graphics. Several movies, including Who Framed Roger Rabbit?, Toy Story, and Stuart Little have received recognition for their innovative use of digital effects and/or animation. Video games use advanced digital graphics. Scientists use computer visualizations to simulate animal movements, thunderstorms, and galaxy formation. Visual simulation is also used in training programs where people learn how to drive or fly. Physicians are able to see digital graphical representations of computerized axial tomography scan data that aid in diagnosis and treatment. Architects and product designers use computer-aided design programs to draw graphical representations of their designs. Graphic designers create digital illustrations on the computer. Across the World Wide Web computer graphics are shared around the globe.

Computer graphics are visual and, therefore, one's response to them is very different from one's response to textual or auditory communication. As children, people develop visual skills before language skills, but even as adults they respond emotionally to what they see. People bring to any viewing of an image their experience, expectations, and values. Sometimes people draw from cultural, religious, or universal symbols to help them relate the image to their experience of the world. The universal becomes personal and the personal becomes universal. Visual communication is multidimensional. People have a primal or visceral response based upon deep-seated beliefs, an emotional response based upon image content and presentation, and an associative response based upon prior experience. Then a rational response is layered on top of the rest.


Computer graphics is the art of using computer technology to create visual images from data. One way to understand this is to contrast film and digital photography. With a film camera a roll of film is loaded into the camera. To make a picture the camera exposes some halide silver crystals on one small piece of film at a time to light. When the entire roll has been used, it may be taken to a professional who processes the film with chemicals and then shines light through the film onto light-sensitive paper. An image soon appears on the paper and a print is created.

Unlike film cameras, a digital camera does not use film. It has a minicomputer inside that records light onto a two-dimensional array of points. Each of these points is then assigned a digital value. In general all digital devices work on the same principle. The source may be light from the natural world or a piece of paper, or an image created on the computer. Each digital device turns the source input into an array of digital values. To better understand this, one needs to look more closely at how computers work.


Computers use a binary system consisting of 1s and 0s. Conceptually this works like an on/off switch. To describe an image in black and white, white can be assigned the value "0" and black the value "1." If one takes a black-and-white image and superimposes a series of rows and columns onto it, then at each intersection of a row and column one has a point. Each point can then be assigned a value of "0," white, or "1," black. Now there is an array of 0s and 1s that taken together represent an image. Every value, that is, every 0 or 1, requires a bit of storage. An image as described above is said to have a bit depth of 1, because it takes 1 bit (either a 1 or 0) to describe any point on the image.

If one wants an image to contain shades of gray between black and white, one need more bits. If one uses 2 bits, there are four possible combinations of 1 and 0

Computer technology
  • Programs are run in batch mode using punch cards. Text characters are used to create pictures.
  • Printers can only print whole characters not individual dots.
  • Mid 1970s: First personal computers appear. Monitors display white text against a green background the result of a P1 phosphor from a cathode ray tube. Monitors are called CRTs or greenscreens.
  • Graphics resolution is low, around 128 × 48 dots per screen.
  • 1981: IBM introduces the first color PC. The CGA monitor is capable of displaying 4 colors using a combination of red, green, and blue.
  • 1984: Apple Macintosh is introduced.
  • Color graphics are possible, but computer memory is limited.
  • 1987: 256 colors and a resolution of 720 dots × 400 dots are possible.
  • The number of colors a PC monitor can display jumps from 256 to 16.7 million.
  • PCs can use 3D graphics.
  • 1994: the World Wide Web becomes available to the public and provides another channel for computer graphics use.
  • LCD monitors become popular.
  • PC Graphics Processing Units (GPU) deliver 25 times the 3D graphics performance of the 1990s.
VideoManufacturers of video games experiment with computer graphics in games such as Pong.
  • Users interact with games through realtime 3D graphical representations of users.
Movies/TV1977: Star Wars incorporates 3D computer graphics into the film.
  • 1984: The Last Starfighter displays the first photorealistic computer graphic images in a feature film.
  • 1988: Who Framed Roger Rabbit combines computer animation characters with live humans.
  • 1991: Toy Story becomes the first computer animated full-length film.
  • 3D computer graphics are used in cartoons on TV and in animated movies.
  • High Definition digital televisions (HDTV) become popular.
  • Shark Tale uses global illumination to render realistic shadows and reflections.
  • Early 1980s: CAD systems using 2D floor planning and rudimentary modeling are available.
  • Late 1980s: CAD systems offer 3D rendering and walkthrough capabilities.
  • 1989: Simulation and visualization programs become available.
  • CAT scan technology which allows physicians to see graphical representations of soft tissue aid in diagnosis and treatment of abnormalities.
  • 3D models of the human body are used for virtual surgery and training.
  • Photographs are integrated with CAD drawings.
  • CAD/CAM programs are used to design, assemble and test new products.

(00, 10, 01, 11), therefore four shades of gray (including black and white) can be represented. Four shades of gray are not generally enough gradation to create a realistic representation. Generally, 8 bits, or 256 shades of gray, are needed to produce a high-quality image.


Color poses an additional complication. All colors can be created by combining the three primary colors of light: red, green, and blue. For a computer to render color effectively it then needs to separately describe each of these three primary colors. Although any color can be created with as few as 2 bits, most computers today use 24-bit or 32-bit depth to represent a full color image, producing up to 16,777,216 colors. This surpasses the capability of the human eye, which can discern about 10 million colors.

The higher the bit depth the more accurate the color is. Even with 16 million colors, however, one may have a low-quality image unless one also has high resolution. Resolution is the density of points, or pixels, on the image arraythat is, the number of columns and rows per inch. The greater the number of columns and rows the higher the density. The higher the density, the greater the resolution.

The cost of high resolution and greater bit depth is space. High-quality graphics take up a large amount of disk space in a computer and require larger memory sizes to work with and edit them. One professional digital image can easily require 50 megabytes, that is, 8,192,000 bits, or more, of space.

Display devices and printers are limited by the amount of data they can represent. The optimal resolution required for a digital image varies based upon the output medium and the number of rows and columns it can display per inch. The resulting intersection points are called dots and the number per inch are called dots per inch, or dpi. Usually a fine-art print will require high resolution, while a Web-based image will not. One of the advantages of digital images is they can be stored on the computer and used repeatedly, each reproduction being exactly the same as the last.

Until recently, before viewing a digital image it had to be converted to a nondigital or analog format because most output devices were analog. Cathode-ray tubes, most televisions, and many printers are still analog, but liquid crystal display monitors and many other printers and televisions are digital. Digital images can go directly from the computer to the output device without translation.

The capabilities and robustness of computer graphics have evolved over several decades. See Table 1 for highlights of the major advancements regarding computer graphics in the fields of computer technology, video, movies and television, and modeling.


Computer graphics will continue to get more sophisticated. Their 3-D photorealistic capabilities and ability to predict changes over time have revolutionized product development and marketing, as well as scientific research and education. They are responsible for superior special effects in movies and on television. Many newspapers and magazines use only computer-generated graphics. They add an aesthetic and emotional dimension to text. Computer graphics affect everyone's life in almost every aspect every day.

see also Information Technology


Maxwell, Marty (2004). The Role of Visual Imagery in Advocacy Journalism. Athens: University of Georgia.

Zenz, Dave (2002, September). Advances in graphics architectures. Retrieved November 14, 2005, from

Marty Maxwell

computer graphics

views updated May 18 2018

computer graphics The creation of, manipulation of, analysis of, and interaction with pictorial representations of objects and data using computers. The information may be a simple histogram, a complex map or engineering design with textual annotation, or a photorealistic rendered scene. The output may be via a transient display such as a cathode-ray tube or as a permanent record via a printer or plotter. Input devices range from digitizers to spaceballs. Interaction with the displayed image is possible.

Output-only computer graphics was used as early as the late 1950s. The first interactive graphics system that defined a number of the current paradigms was Sketchpad, devised by Ivan Sutherland at MIT Lincoln Laboratory and published in 1963.

computer graphics

views updated May 17 2018

computer graphics Illustrations produced on a computer. Simple diagrams and shapes may be produced by typing on the keyboard. Complex images require a mouse, painting or drawing software and often special graphics hardware.

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