Introduction to graphics

Introduction to graphics
Mrs.Sowmya Jyothi
Assistant Professor
Mangalore

1. Introduction to Computer Graphics and
Display Systems
The objective of this chapter is
Tounderstandthebasicsofcomputergraphics.
Tobeawareofapplicationsofcomputergraphics.
Toknowtheelementsofcomputergraphics.
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2. ComputerGraphicsistheuseofcomputerstodisplayand
manipulateinformationingraphicalorpictorialform,eitherona
visual-displayunitorviaaprinterorplotter.
Computergraphicsinvolvesdisplay,manipulationandstorageof
picturesandexperimentaldataforpropervisualizationusinga
computer.
Itprovidesmethodsforproducingimagesandanimations
(sequenceofimages).Itdealswiththehardwareaswellas
softwaresupportforgeneratingimages.
In1960,WilliamA.Fetter,anartdirectoratTheBoeingCompany
inSeattle,Washington,coinedtheterm“computergraphics.”
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3. COMPUTERANIMATION
Computeranimationistheartofcreatingmovingimagesvia
theuseofcomputers.Itisasubfieldofcomputergraphicsand
animation.Increasinglyitiscreatedbymeansof3Dcomputer
graphics.
Animation:referstothesimulationofsequenceofimages
overtime.
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4. INTRODUCTION TO IMAGE AND OBJECTS
Animageisbasicallyrepresentationofarealworldobjectona
computer.Itcanbeanactualpicturedisplay,astoredpageina
videomemory,orasourcecodegeneratedbyaprogram.
Mathematically,animageisatwo-dimensionalarrayofdata
withintensityoracolorvalueateachelementofthearray.
Objectsarerealworldentitiesdefinedinthree–dimensional
worldcoordinates.Incomputergraphicswedealwithboth2D
and3Ddescriptionsofanobject.
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6. 1.CAD(Computer-AidedDesign)-Amajoruseofcomputer
graphicsisindesignprocesses,particularlyforengineeringand
architecturalsystems.Computer-Aideddesignmethodsare
routinelyusedinthedesignofbuildings,automobiles,aircraft,
spacecraft,computers,textilesandmanyotherproducts.
AnimationsareoftenusedinCADapplications.
2.PresentationGraphics-Itisusedtoproduceillustrationsfor
reportsortogenerateslidesforusewithprojectors.
Presentationgraphicsisusedtosummarizefinancial,statistical,
mathematical,scientificandeconomicdataforresearchreports,
managerialreportsandothertypesofreports.Examplesof
presentationgraphicsarebarcharts,linegraphs,surfacegraphs,
piechartsanddisplaysshowingrelationshipsbetween
parameters.
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7. 3.ComputerArt
Avarietyofcomputermethodsareavailableforartistsfor
designingandspecifyingmotionsofanobject.
Computergraphicsmethodsarewidelyusedinbothfineart
andcommercialartapplications.
Tocreatepictures,theartistusesacombinationof3D
modelingpackages,texturemapping,drawingprogramsand
aCADsoftware.Forexample:Cartoondrawingproducedwith
apaintbrushprogram.
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8. 4. Entertainment –
Inmakingmotionpictures,musicvideosandtelevision
shows,computergraphicsmethodsarewidelyused.
Graphicsobjectscanbecombinedwithliveactionsorcanbe
usedwithimageprocessingtechniquestotransformone
objecttoanother(morphing).
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9. 5.EducationAndTraining–
Computer-generatedmodelsofphysical,financialand
economicsystemsareoftenusedaseducationalaids.
Computergraphicscanmakeusunderstandthefunctioningof
asysteminabetterway.
Insometrainingsystems,graphicalmodelswithsimulations
helpatraineetotraininvirtualrealityenvironment.
Forexample,practicesessionortrainingofshipcaptains,
aircraftpilots,airtrafficcontrolpersonnel.
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10. 6. Visualization
The numerical and scientific data are converted to a visual form
for analysis and to study the behavior called visualization.
Producing graphical representation for scientific data sets are
called scientific visualization.
Business visualization is used to represent the data sets related
to commerce and industry.
The visualization can be either 2D or 3D.
For analyzing scientific, engineering, medical and business data or behavior where we have to deal with large amount of information, it is very tedious and ineffective process
to determine trends and relationships among them. But if it is converted into visual form, it becomes easier to understand. This process is termed as visualization.
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11. 7.ImageProcessing
Computergraphicsisusedtocreateapicture.
Image processing applies techniques to modify or interpret
existing pictures. One can improve picture quality through image
processing techniques.
Toapplyimageprocessingmethods,theimagemustbedigitized
first.
Medicalapplicationsalsomakeextensiveuseofimageprocessing
techniquesforpictureenhancements,simulationsofoperations,
etc.
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12. 8. Graphical User Interface
Nowadays software packages provide graphics user interface (GUI) for
the user to work easily.
A major component in GUI is a window.
Multiple windows can be opened at a time.
To activate any one of the window, the user needs just to check on that
window.
Menus and icons are used for fast selection of processing operations.
Icons are used as shortcut to perform functions. Icons take less screen
space. Some other interfaces like text box, buttons, and list are also
used.
GUI commonly used these days to make a software package more interactive. There are multiple
window system, icons, menus, which allows a computer setup to be utilized more efficiently.
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13. IMAGE REPRESENTATION
Imagerepresentationistheapproximationsofthereal
worlddisplayedinacomputer.
A picture in computer graphics is represented as a
collection of discrete picture elements termed as pixels.
A pixel is the smallest element of picture or object that can
be represented on the screen of a devicelike computer.
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14. BITMAP AND VECTOR –BASED GRAPHICS
Thereare two typesof computergraphics:
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15. 1.RasterorBitmapgraphics
Abitmapimageusesagridofindividualpixelswhereeach
pixelcanbeadifferentcolororshade.
Bitmapsarecomposedofpixelswhereeachpixelis
separatelydefined(asinadigitalphotograph).Imageswith
highernumbersofpixelshavehigherresolution.
Thejaggedappearanceofbitmapimagescanbepartially
overcomewiththeuseof"anti-aliasing"
Bitmapimagesrequirehigherresolutionsandanti-aliasingfor
asmoothappearance.
Bitmapsarebestusedforphotographsandimageswithsubtle
shading.ForExample-Photoshop,Paint,etc.
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16. 2.Vectorgraphicswheremathematicalformulasareusedto
drawlinesandshapes,whicharetheninterpretedatthe
viewer'sendtoproducethegraphic.
Vector-basedgraphicsontheotherhandaremathematically
describedandappearsmoothatanysizeorresolution.
Graphicsbestsuitedforthevectorformatarepagelayout,type,
lineartorillustrations.
ForExample-CorelDraw,AdobeIllustrator,etc.
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17. BITMAP/RASTER IMAGE VECTOR IMAGE
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18. Bitmap graphics:
It is pixel based graphics.
The position and color information about the image
are stored in pixels arranged in grid pattern.
The Image size is determined on the basis of image
resolution.
These images cannot be scaled easily.
Bitmapimagesareusedtorepresentphotorealistic
imageswhichinvolvecomplexcolorvariations
Vector graphics:
The images in vector graphics are basically
mathematically based images.
Vector based images have smooth edges and
therefore used to create curves and shapes.
These images are appropriate for precise illustrations
but not good for photorealistic images
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20. DISPLAYDEVICES
Inagraphicalsystem,videomonitoristheprimaryoutput
deviceandCathodeRayTube(CRT)isthemainelementof
avideomonitor.
There are various types of displays like CRT, LCD and Plasma.
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21. 1.CRT(CathodeRayTube)isoneofthemostlyuseddisplaytechnology.
MostdesktopcomputerdisplaysuseofCRTs.
TheCRTinacomputerdisplayissimilarto“PictureTube”inaTelevision
Receiver.
CRTisaspecializedvacuumtubeinwhichimagesareproducedwhenan
electronbeamstrikesaphosphorscentsurface.
CRTshave3mainelements:anelectrongun,adefectingsystemanda
screen.
InCRT,abeamofelectronsemittedbyanelectrongunstrikesonspecified
positionsonphosphorcoatedscreenafterpassingthroughfocusingand
deflectingsystems.
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23. WORKING OF CRT
1.Abeamofelectronsorcathoderaysareemittedbyelectron
gun.
2.Throughthefocusinganddeflectingsystems,theelectronbeam
passesandisdirectedtowardsspecifiedpositionsonthe
phosphor-coatedscreen.
3.Whenthebeamhitsthescreen,asmallspotoflightisemitted
ateachpositioncontactedbytheelectronbeam.
4.Thepictureisredrawnbydirectingtheelectronbeambackover
thesamescreen.
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24. Types of LCD
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26. Flat-PanelDevicesarethedevicesthathavelessvolume,weight,
andpowerconsumptioncomparedtoCathodeRayTube(CRT).
DuetotheadvantagesoftheFlat-PanelDisplay,useofCRT
decreased.
AsFlatPanelDevicesarelightinweightsthat’swhytheycanbe
hangonwallsandwearthemonourwristasawatch.
FlatPanelDisplay(FPD)allowuserstoviewdata,graphics,text
andimages.
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28. 1.EmissiveDisplay:
TheEmissiveDisplayorEmittersarethedevicesthatconvert
electricalenergyintolightenergy.
Examples:PlasmaPanel,LED(LightEmittingDiode),Flat
CRT.
2.Non-EmissiveDisplay:
Non-EmissiveDisplayorNon-Emittersarethedevicesthatuse
opticaleffectstoconvertsunlightorsomeothersourceinto
graphicpatterns.
Examples:LCD(LiquidCrystalDisplay)
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29. 2. LCD Display: Liquid Crystal Display
LCDisthetechnologyusedfordisplaysinnotebooks,laptopsandothersmaller
computers.LCDsallowdisplaystobemuchthinnerthanCRTtechnology.
LiquidCrystalDisplaysarethedevicesthatproduceapicturebypassing
polarizedlightfromthesurroundingsorfromaninternallightsourcethrougha
liquid-crystalmaterialthattransmitsthelight.
LCDusestheliquid-crystalmaterialbetweentwoglassplates;eachplateisthe
rightangletoeachotherbetweenplatesliquidisfilled.
Oneglassplateconsistsofrowsofconductorsarrangedinverticaldirection.
Anotherglassplateisconsistingofarowofconductorsarrangedinhorizontal
direction.
Thepixelpositionisdeterminedbytheintersectionofthevertical&horizontal
conductor.Thispositionisanactivepartofthescreen.
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30. 3. Plasma Displays
Aplasmadisplayisacomputervideodisplayinwhich
eachpixelonthescreenisilluminatedbyatinybitofplasma
orchargedgas,somewhatlikeatinyneonlight.
Plasmadisplaysarethinnerthancathoderaytube(CRT)
displaysandbrighterthanliquidcrystaldisplays(LCD).
Plasmadisplaysaresometimesmarketedas"thin-panel"
displaysandcanbeusedtodisplayeitheranalogvideosignals
ordisplaymodesdigitalcomputerinput.
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32. Display Technology
A. Raster Scan Systems
Itisthemostcommontypeofgraphicsmonitorbasedontelevision
technology.
Inarasterscansystem,theelectronbeamissweptacrossthescreen,one
rowatatimefromtoptobottom.
Whenelectronbeammovesacrosseachrowthebeamintensityisturned
ONandOFFtocreateapatternofilluminatedspots.
Picturedefinitionisstoredinamemoryareacalledtherefreshbufferor
framebufferusedforredrawn.Horizontalretrace:Thereturntotheleftof
thescreen,afterrefreshingeachscanline.
Verticalretrace:Attheendofeachframetheelectronbeamreturnstothe
topleftcornerofthescreentobeginthenextframe.
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35. A. Raster Scan Systems
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36. 2.Random-ScanDisplays
TheCRThastheelectronbeamdirectedonlytothepartsofthescreen
whereapictureistobedrawn.
Random-scanmonitorsdrawapictureonelineatatime,calledas
vectordisplay.
Refreshratesonaransom-scansystemdependsonthenumberoflines
tobedisplayed.
Picturedefinitionisstoredasasetofline-drawingcommandsinthe
refreshdisplayfileorrefreshbuffer.
Todisplayaspecifiedpicture,thesystemcyclesthroughthesetof
commandsinthedisplayfile,drawingeachcomponentline.
Thesesystemsaredesignedfortheline-drawingapplicationsandcan’t
displayrealisticshadedscenes.
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37. Random-Scan Displays
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COLORCRTMONITORS
AcolorCRTmonitordisplayscolorpicturebyusinga
combinationofphosphorsthatemitdifferentcoloredlight.
Bycombiningtheemittedlightarangeofcolorscanbe
generated.
Therearebasicmethodsfordisplayingcolordisplays.
1.BeamPenetrationMethod
2.Shadow-MaskMethod

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41. 1.BeamPenetrationMethod
BeamPenetrationMethodisquitesimilartothenormalCRTanditusesonly
oneelectrongun.
TheBeam-Penetrationmethodhasbeenusedwithrandom-scanmonitors.
Inthismethod,theCRTscreeniscoatedwithtwolayersofphosphor,redand
greenandthedisplayedcolordependsonhowfartheelectronbeam
penetratesthephosphorlayers.
Thismethodproducesfourcolorsonly,red,green,orangeandyellow.
Abeamofslowelectronsexcitestheouterredlayeronly;hencescreenshows
redcoloronly.
Abeamofhigh-speedelectronsexcitestheinnergreenlayer.Thusscreenshows
agreencolor.
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42. Advantages:
Inexpensive
Disadvantages:
Only four colors are possible
Quality of pictures is not as
good as with another method.
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BeamPenetrationMethod

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2.ShadowMaskMethod:
ShadowMaskMethodiscommonlyusedinRaster-ScanSystem
becausetheyproduceamuchwiderrangeofcolorsthanthebeam-
penetrationmethod.
Inthisthepixelismadeupofthree-colors.Soduetothreecolorsit
usesthreeelectrongunsoneforproducingeachcolor.Thecolors
arered,greenandblue.Inthistheimportantconsiderationfora
colormonitoristhesettingofelectrongunsandthephosphordots
formingapixel.
ItisusedinthemajorityofcolorTVsetsandmonitors.

44. Construction:
A shadow mask CRT has 3 phosphor color dots at each pixel position.
One phosphor dot emits: red light
Another emits: green light
Third emits: blue light
This type of CRT has 3 electron guns, one for each color dot and a
shadow mask grid just behind the phosphor coated screen.
Shadow mask grid is pierced with small round holes in a triangular
pattern.
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45. Shadow Mask Method :
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46. 4.DirectViewStorageTube(DVST)resemblesCRTasituseselectrongun
todrawpictureandphosphorcoatedscreentodisplayit.
Thephosphorusedinthisisofhighpersistence.
DVSTdoesnotuserefreshbufferorframebuffertostorepicture
definition.
PicturedefinitionisstoredininsideCRTinformpositivecharged
distribution.BecauseofthisreasonDVSTisknowsasStorageTypeCRT.In
DVSTnorefreshingisrequiredasresultpicturedrawnonDVSTwillbe
seenforseveralminutesbeforefading.
Functionofguns:TwogunsareusedinDVST
Primaryguns:Itisusedtostorethepicturepattern.
FloodgunorSecondarygun:Itisusedtomaintainpicturedisplay.
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47. Direct View Storage Tube (DVST)
Advantage:
No refreshing is needed.
High Resolution
Cost is very less
Disadvantage:
Itisnotpossibletoerasethe
selectedpartofapicture.
Itisnotsuitablefordynamic
graphicsapplications.
Ifapartofpictureistomodify,
thentimeisconsumed.
Thesesystemsdonotdisplay
colors.
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