Pixel, frame, buffer, application of computer graphics, Raster Graphics fundamentals. Display Devices- Random Scan, Raster Scan Monitors, Color CRT Monitor, DVST and Plasma Panel

1. Introduction
to
Computer Graphics and
Multimedia

2. Overview
 What is Computer Graphics?
 Classification of Computer Graphics
 Components of Computer Graphics
 Display Devices
 Random Display Architecture
 Raster Display Architecture
 Concept of Frame Buffer
 Advantages
 Applications

3. What is Computer Graphics?
 Creation, Storage and Manipulation of pictures and
drawing using a digital computer.
 Effective tool for presenting information.
 It is important to understand –
 How pictures or graphics objects are presented in
computer graphics?
 How pictures or graphics objects are prepared for
presentation?
 How previously prepared pictures or graphics objects
are presented?
 How interaction with pictures or graphics objects is
accomplished?

4. What is Computer Graphics?
 Pictures or graphics objects are presented as collection of
discrete picture elements.

5. Some Basic Concepts of Computer
Graphics
 Refresh Rate
◦ Number of times per second the image is redrawn (e.g., 60 or
higher)
 Resolution
◦ The maximum number of points that can be displayed without
overlap on a CRT.
◦ Resolution depends on the type of phosphor, the intensity to
be displayed, focusing and deflection systems, size of
video memory.
 Pixel
◦ One dot or picture element of the image or graphical object.
 Aspect Ratio
◦ Ratio of vertical points to horizontal points necessary to
produce equal-length line in both direction.
◦ 4/3 : length of 4 points on horizontal line = length of 3 points
on vertical line.

6. Classification of Computer Graphics
Passive Computer Graphics Vs Interactive Computer
Graphics
Parameter
Passive Computer
Graphics
Interactive Computer
Graphics.
Control No control Dynamic nature
Communicatio
n
One way
communication
Two way communication
Interaction
No interaction between
user and H/w
High bandwidth user
interaction
Supported Earlier Modern applications
Motion &
Updation
No facility 2-D, 3-D transformations

7. Classification of Computer Graphics
Bitmapped Graphics Vs Vector Graphics
Parameter Bitmapped Graphics Vector Graphics
What are they
made up of?
Pixels Objects
What can be
edited?
Individual pixels Individual objects
What is the file
size?
Large, as the
computer stores
details of every pixel
Small, as the computer
stores details of objects,
which do not require
much memory
What happens
when they are
resized?
They lose quality They do not lose quality

8. Components of Computer Graphics
 Digital Memory Buffer.
 TV Monitor.
 Display Controller.
CPU
Video
Monitor
Display
Controller
Frame
Buffer
Update
Process Process
Refresh
Information
Pixel

9. Display Devices
 They are used for graphic display. The
display system may be attached with a pc
to display character, picture and video
output.
 Some common types of display systems
are:
◦ Raster Scan Display
◦ Random Scan Display
◦ DVST
◦ Flat Panel Display

10. Display Devices (contd...)
 CRT (Cathode Ray Tube) –
 The cathode ray tube (CRT) is a vacuum
tube containing an electron gun and
a fluorescent screen, with internal or external
means to accelerate and deflect the electron
beam.
 Create images in the form of light emitted from
the fluorescent screen.
 In all modern CRT monitors and televisions, the
beams are bent by magnetic deflection.

11. Display Devices (contd...)
 Basic CRT (Cathode Ray Tube) –

12. Display Devices (contd...)
 Basic CRT (Cathode Ray Tube) –
1. Electron Guns
2. Electron Beams
3. Focusing Coils
4. Deflection Coils
5. Anode Connection
6. Shadow Mask
7. Phosphor layer
8. Close-up of the phosphor coated inner side

13. Display Devices (contd...)
 CRT (Cathode Ray Tube) –
◦ Phosphor persistence –
 A phosphor’s persistence is defined as the time
from the removal of excitation to the moment of
decaying the light to one-tenth of its original
intensity.
 Low persistence -> good for animation.
 High persistence -> good for static picture with high
complexity.
◦ Refresh Rate (RR)
 Number of times per second the image is redrawn
(e.g., 60 or higher)

14. Color CRT Monitors
 A CRT monitor displays color pictures by using a
combination of phosphors that emit different
colorlights.
◦ Two methods are there :
Beam Penetration Method
Shadow Mask Method

15. Color CRT Monitors (contd...)
 Beam Penetration Method-
 Two layers of phosphor (red and green) are coated
onto the inside of the CRT screen.
 The display color depends on how far the electron
beam penetrates into the phosphor layers.
 The speed of the electrons, and the screen color at
any point, is controlled by the beam acceleration
voltage.
 Only four colors are possible (red, green, orange, and
yellow).
 Quality of pictures is not as good as with other
methods.

16. Color CRT Monitors (contd...)
 Beam Penetration Method-

17. Color CRT Monitors (contd...)
 Shadow Mask Method-
 Three color phosphor dots (red, green and blue)
at each point on the screen.
 Three electron guns, each controlling the display
of red, green and blue light.
 We obtain color variations by varying the
intensity levels of the three electron beam.
 The delta-delta method and In-line method.

18. Color CRT Monitors (contd...)
 The in-line method:

19. Color CRT Monitors (contd...)
 The delta-delta method:

20. Random Display Architecture

21. Raster Display Architecture

22. Random Scan System Vs Raster Scan
System
Random Scan System Raster Scan System
Cannot draw realistic shaded
scenes.
Used in systems to display realistic
images.
Store - Line drawing instruction
Store – Value related to pixels
(Intensity
value)
Higher resolution No support for high resolution
Smooth line drawings Capable of producing curves better
Cannot produce contrast,
memory
doesn't store intensity value of
pixel
Picture with better contrast
Costlier
Cost not too high as compared to
Random Scan
Line Drawing, Known as Vector

23. Concept of Frame Buffer
 A block of memory, dedicated to graphics output,
that holds the contents of what will be displayed.
 A frame buffer may be thought of as computer
memory organized as a two-dimensional array with
each (x,y) addressable location corresponding to
one pixel.
 Bit Planes or Bit Depth is the number of bits
corresponding to each pixel.
 A typical frame buffer resolution might be
640 x 480 x 8
1280 x 1024 x 8
1280 x 1024 x 24

24. Concept of Frame Buffer
 1-Bit Memory. Monochrome Display (Bit-map
Display)
Electron
Gun
1 bit
2 levels

25. Concept of Frame Buffer
 3-Bit Color Display
3
red
green
blue
COLOR: black red green blue yellow cyan magenta white
R
G
B
0
0
0
1
0
0
0
1
0
0
0
1
1
1
0
0
1
1
1
0
1
1
1
1

26. Concept of Frame Buffer
 True Color Display
24 bit planes, 8 bits per color gun. 224 =
16,777,216 colors

27. Advantages of Computer Graphics
 High quality graphics display.
 Show moving pictures, animation.
 Display geometric relationships of objects.
 Provide tool called motion dynamics.
 Update Dynamics.

28. Applications of Computer Graphics
• GUI's,
• Plotting in business,
• Plotting in science and technology,
• Scientific Visualization
• Office automation
• Desktop publishing,
• Web/business/commercial publishing and
advertisements,
• CAD/CAM design,
• Simulation studies,
• Simulators
• Cartography,
• Multimedia,
• Entertainment (movie, TV, Advt. Etc. )
• Virtual reality

29. Thank You !!!