3. Computer graphics is the creation and manipulation of geometric
objects (models) and images using computer.
Computer graphics is concerned with all aspects of producing pictures
or images using a computer.
Computer graphics is involved in any work that uses computation to
create or modify images, whether those images are still or moving;
interactive or fixed; on film, video, screen, or print.
4. The applications of computer graphics are many and varied; we can, however, divide them
into four major areas:
1. Display of information (Graphs, Maps, and Medical images)
2. Design (Engineering etc)
3. Simulation and animation (Training, Games, Movies, Virtual Reality and Scientific
4. User interfaces (Operating systems and application software)
Many applications may span two or more of these areas.
35. • There are six major hardware elements in a computer graphics system:
1. Input devices
Central Processing Unit
Graphics Processing Unit
4. Output devices
37. • There are ways images are represented on digital output devices
Raster and Vector.
• Virtually all modern graphics systems are raster based. The image
we see on the output device is an array—the raster—of picture
elements, or pixels, produced by the graphics system.
Vector Systems on the
other hand represent
an image as collection
40. *Each pixel corresponds to a location, or small area, in the image.
*Collectively, the pixels are sored in a part of memory called the
*The frame buffer can be viewed as the core element of a graphics
*Its resolution - the number of pixels in the frame buffer - determines
the detail that you can see in the image. E.g. 1024 * 768 (=786,432
41. *The depth or precision of the frame buffer, defined as the number of
bits that are used for each pixel, determines properties such as how
many colors can be represented on a given system.
*For example, a 1-bit-deep frame buffer allows only 2 colors (21),
whereas an 8-bit-deep frame buffer allows 256 colors (28).
*In full-color systems, there are 24 (or more) bits per pixel. Such
systems can display sufficient colors to represent most images
realistically. They are also called true-color systems, or RGB-color
systems, because individual groups of bits in each pixel are assigned to
each of the three primary colors—red, green, and blue—used in most
42. 1 bit (2 colors) 2 bit (4 colors) 4 bit (16 colors)
8 bits (256 colors) 24 bits (16,777,216 colors) 32 bits (4,294,967,296 colors)
43. *In a simple system, there may be only one processor, the central processing
unit (CPU) of the system, which must do both the normal processing and the
*The main graphical function of the processor is to take specifications of
graphical primitives (such as lines, circles, and polygons) generated by
application programs and to assign values to the pixels in the frame buffer that
best represent these entities.
*For example, a triangle is specified by its three vertices, the graphics system
must generate a set of pixels that appear as line segments to the viewer. The
conversion of geometric entities to pixel colors and locations in the frame buffer
is known as rasterization, or scan conversion.
*Graphics Processing Units (on modern systems) on the other hand are
dedicated processing units specialized in (the above) graphic functions.
46. • Dot Matrix - uses a head with 7 to 24 pins to strike a ribbon
(single or multiple color)
47. • Ink Jet Printers: a printer in which the characters are formed
by minute jets of ink. (fires small balls of colored ink)
• Laser Printers: a printer linked to a computer producing
printed material by using a laser to form a pattern of
electrostatically charged dots on a light-sensitive drum,
which attract toner (or dry ink powder). The toner is
transferred to a piece of paper and fixed by a heating
48. •3D Printers: a machine allowing the creation of a physical
object from a three-dimensional digital model, typically by
laying down many thin layers of a material in succession.
49. • In a raster system, the graphics system takes pixels
from the frame buffer and
displays them as points on the surface of the display.
• Cathode Ray Tube (CRT)
• Liquid Crystal Display (LCD)
• Light Emitting Diode (LED) Display
50. When electrons strike the phosphor coating on the tube, light is emitted.
The direction of the beam is controlled by two pairs of deflection plates.
Light appears on the surface of the CRT when a sufficiently intense beam of electrons is
directed at the phosphor.
51. The screen is coated
with phosphor, 3 colors
for a color monitor.
For a color monitor,
three guns light up red,
green, or blue
52. Liquid crystal displays use small flat chips which change their
transparency properties when a voltage is applied.
LCD elements are arranged in an n x m array call the LCD matrix
LCDs elements do not emit light, but use backlights behind the LCD
Color is obtained by placing filters in front of each LCD element
Image quality dependent on viewing angle.
53. Also divided into pixels, but without an electron gun firing at a
screen, LCDs have cells that either allow light to flow through, or
55. There are two primary types of input devices:
Pointing devices and Keyboard devices.
The pointing device allows the user to indicate a position on the screen and almost
always incorporates one or more buttons to allow the user to send signals to the
computer (mouse, joystick, touch screen and spaceballs).
The keyboard device is almost always a physical keyboard but can be generalized to
include any device that returns character codes.
57. Special Purpose
Word, Excel etc.
Simulation Packages - Simio
Animation and Compositing Packages e.g. Autodesk Maya
Visualization Packages e.g. GraphViz
Painting Packages e.g. MSPaint
Programming API (Application Program Interface)
Java2D and Java3D
58. Programmer sees the graphics system through an interface: the
Application Programmer Interface (API)
High Level API (Java3D)
Low-Level Application Programming Interface (OpenGL)
Hardware and software
Output Devices Input Devices