Introduction to computer graphics and multimedia

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,StorageandManipulationofpicturesand
drawingusingadigitalcomputer.
Effectivetoolforpresentinginformation.
Itisimportanttounderstand–
Howpicturesorgraphicsobjectsarepresentedin
computergraphics?
Howpicturesorgraphicsobjectsarepreparedfor
presentation?
Howpreviouslypreparedpicturesorgraphicsobjects
arepresented?
Howinteractionwithpicturesorgraphicsobjectsis
accomplished?

4. What is Computer Graphics?
Picturesorgraphicsobjectsarepresentedascollectionof
discretepictureelements.

5. Some Basic Concepts of Computer
Graphics
RefreshRate
◦Numberoftimespersecondtheimageisredrawn(e.g.,60or
higher)
Resolution
◦Themaximumnumberofpointsthatcanbedisplayedwithout
overlaponaCRT.
◦Resolutiondependsonthetypeofphosphor,theintensityto
be displayed,focusinganddeflectionsystems,sizeof
videomemory.
Pixel
◦Onedotorpictureelementoftheimageorgraphicalobject.
AspectRatio
◦Ratioofverticalpointstohorizontalpointsnecessaryto
produceequal-lengthlineinbothdirection.
◦4/3:lengthof4pointsonhorizontalline=lengthof3points
onverticalline.

6. Classification of Computer Graphics
Passive Computer Graphics Vs Interactive Computer
Graphics
Parameter
Passive Computer
Graphics
Interactive Computer
Graphics.
Control No control Dynamicnature
Communicatio
n
Oneway
communication
Two way communication
Interaction
No interactionbetween
user and H/w
High bandwidth user
interaction
Supported Earlier Modernapplications
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 Individualobjects
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 qualityThey 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
Theyareusedforgraphicdisplay.The
displaysystemmaybeattachedwithapc
todisplaycharacter,pictureandvideo
output.
Somecommontypesofdisplaysystems
are:
◦Raster Scan Display
◦Random Scan Display
◦DVST
◦Flat Panel Display

10. Display Devices (contd...)
CRT (Cathode Ray Tube) –
Thecathoderaytube(CRT)isavacuum
tubecontaininganelectrongunand
afluorescentscreen,withinternalorexternal
meanstoaccelerateanddeflecttheelectron
beam.
Createimagesintheformoflightemittedfrom
thefluorescentscreen.
InallmodernCRTmonitorsandtelevisions,the
beamsarebentbymagneticdeflection.

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 –
Aphosphor’spersistenceisdefinedasthetime
fromtheremovalofexcitationtothemomentof
decayingthelighttoone-tenthofitsoriginal
intensity.
Lowpersistence->goodforanimation.
Highpersistence->goodforstaticpicturewithhigh
complexity.
◦Refresh Rate (RR)
Numberoftimespersecondtheimageisredrawn
(e.g.,60orhigher)

14. Color CRT Monitors
ACRTmonitordisplayscolorpicturesbyusinga
combinationofphosphorsthatemitdifferent
colorlights.
◦Twomethodsarethere:
BeamPenetrationMethod
ShadowMaskMethod

15. Color CRT Monitors (contd...)
Beam Penetration Method-
Twolayersofphosphor(redandgreen)arecoated
ontotheinsideoftheCRTscreen.
Thedisplaycolordependsonhowfartheelectron
beampenetratesintothephosphorlayers.
Thespeedoftheelectrons,andthescreencolorat
anypoint,iscontrolledbythebeamacceleration
voltage.
Onlyfourcolorsarepossible(red,green,orange,and
yellow).
Qualityofpicturesisnotasgoodaswithother
methods.

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

17. Color CRT Monitors (contd...)
Shadow Mask Method-
Threecolorphosphordots(red,greenandblue)
ateachpointonthescreen.
Threeelectronguns,eachcontrollingthedisplay
ofred,greenandbluelight.
Weobtaincolorvariationsbyvaryingthe
intensitylevelsofthethreeelectronbeam.
Thedelta-deltamethodandIn-linemethod.

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
Display
Mainly used for Point Plotting

23. Concept of Frame Buffer
Ablockofmemory,dedicatedtographicsoutput,
thatholdsthecontentsofwhatwillbedisplayed.
Aframebuffermaybethoughtofascomputer
memoryorganizedasatwo-dimensionalarraywith
each(x,y)addressablelocationcorrespondingto
onepixel.
BitPlanesorBitDepthisthenumberofbits
correspondingtoeachpixel.
Atypicalframebufferresolutionmightbe
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 ColorDisplay
24 bit planes, 8 bits per color gun. 2
24
=
16,777,216 colors

27. Advantages of Computer Graphics
Highqualitygraphicsdisplay.
Showmovingpictures,animation.
Displaygeometricrelationshipsofobjects.
Providetoolcalledmotiondynamics.
UpdateDynamics.

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 !!!