GKS presantation
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Transcript of GKS presantation
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Graphical Kernel SystemGKS
Computer GraphicsCST301-2
Computer Science & Technology
Group #1
Uva Wellassa University
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DEFINIT
ION
GKS defines a common interface tointeractive computer graphics forcreating, manipulating, and displayingor printing computer graphics ondifferent types of computer graphics
output devices
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Introduction
w as the first ISO standard for lo w -level computer graphics ( ISO 10303-46)provides a set of dra w ing features fort w o-dimensional vector graphics suitable for charting and similar duties
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designed to be portable acrossdifferent programming languages graphics devices Hard w are
Applications w ritten in GKS w ill bereadily portable to many platforms anddevices
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Historyintroduced in 1977 by Jos LuisEncarnao (Joseph Luis Incarnation )fairly common on computerw orkstations in the 1980s andearly 1990slatter w as common on the Atari ST is a home/personal computer released by Atari Corporation in 1985
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Standards D ata model standard - ISO 10303-46 AN SI standard - AN SI X3.124 ISO standard - ISO / IE C 7942Language bindings ISO standard - ISO 8651GKS-3D ISO standard - ISO 8805C bindings standard - ISO 8806
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Objectives of the GKS
production and manipulation of picturesSuch pictures vary from simple line graphs engineering dra w ings integrated circuit layouts images representing medical data astronomical data
E ach of these various pictures can bedescribed by GKS
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Main
Primitives in GKS
1. Polyline - dra w s a sequence ofconnected line segments
2. Polymarker - marks a sequence of pointsw ith the same symbol
3. Fill area - displays a specified area
4. Text - dra w s a string of characters5. Cell array - displays an image composed
of a variety of colours or grey scales
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Parameters
Set of parameters are associated w itheach primitivesUsed to define particular instances ofthat primitive
F or example, the parameters of thetext primitive : String or characters to be dra w n Starting position of that string
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Attributes
A lthough the parameters define theprimitives to be specified
additional data are necessary to describethe actual appearance of the primitivesThese additional data are kno w n asAttributes
F or example, in text primitive height of a character string angle at w hich it is to be dra w n
O nce a attribute is define several primitivescan be plotted using that attribute
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Coordinate SystemsConsists of 2-axis X axis and Y axis
Unit length on the t w o axes can be same A lso it is possible to define differentialscaling on the t w o axes
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User Coordinates
The user w ill have a preferred coordinatesystem in w hich he w ould like to w ork
That is kno w as user coordinatesMost frequently, this coordinate system w illbe a Cartesian coordinate system
It is also possible that the user coordinatesystem might be logarithmically scaled or
polar coordinates But GKS only understood Cartesiancoordinate systems
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World Coordinates
If the user coordinate system is notCartesian
The user himself must map his coordinatesystem onto a Cartesian systemTo differentiate bet w een the preferreduser coordinates and the ones presentedto GKSThe term w orld coordinates (WC) is used
to define a coordinate system used topresent graphical output to GKS
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PolylineThe main line dra w ing primitive of GKS
F unction : POLYLINE(N, XPTS, YPTS)XPTS and YPTS are arrays giving the N points(XPTS(1), YPTS(1)) to (XPTS(N),
YPTS(N))Generated consists of N - 1 line segmentsjoining adjacent points starting w ith the
first point and endingw
ith the last
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E x: P lot a graph of a set of data, usingset of ordered pairs (X, Y)
R EAL XDK(19), YDK(19)
DATA XDK/O.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,
16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0/
DATA YDK/8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,13.2/
POLYLINE(19, XDK, YDK)
R EAL XDK(19), YDK(19)
DATA XDK/O.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,
16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0/
DATA YDK/8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,13.2/
POLYLINE(19, XDK, YDK)
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Above code segment w ill produces the outputgiven belo w
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Ploymarker
Instead of dra w ing lines, mark the setof pointsP olymarker places a centred marker ateach point
F unction: POLYMAR KER (N, XPTS,
YPTS) Arguments are the same as for thepolyline function
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E x: P lot a data points of set of data,using set of ordered pairs (X, Y)
R EAL XDK(19), YDK(19)
DATA XDK/O.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,
16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0/
DATA YDK/8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,13.2/
POLYMAR KER (l9, XDK, YDK)
R EAL XDK(19), YDK(19)
DATA XDK/O.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,
16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0/
DATA YDK/8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,13.2/
POLYMAR KER (l9, XDK, YDK)
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Fill AreaLine dra w ings are insufficient for manyapplications
Define a fill areaWhich can completely fill an area
w ith a single colour by repeating a pattern
An array of points is specified w hichdefines the boundary of the area
If the area is not close GKS join the last
point to the first point
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F unction : F ILL A R EA(N, XPTS,YPTS)
R EAL XDK(43), YDK(43)
DATA XDK/0.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0, 28.8, 27.2, 25.0, 23.0, 21.5, 21.1, 21.5,22.8, 24.1, 25.1, 25.2, 24.2, 22.1, 20.0, 18.0, 16.0,14.0, 12.0, 10.0, 8.0, 6.1, 4.2, 3.0, 1.3/
DATA YDK/ 8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,
13.2, 12.3, 11.5, 11.5, 11.5, 11.2, 10.5, 9.0, 8.0, 7.0,5.1, 3.6, 1.9, 1.1, 0.9, 0.7, 0.8, 1.0, 1.0, 1.2, 1.8,2.1, 2.9, 4.1, 6.0/
SET F ILL A R EA INDEX(1)
F ILL A R EA(43, XDK, YDK)
R EAL XDK(43), YDK(43)
DATA XDK/0.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0,16.4, 17.0, 17.3, 17.8, 18.5, 20.0, 22.0, 24.0, 26.0,28.0, 29.0, 28.8, 27.2, 25.0, 23.0, 21.5, 21.1, 21.5,22.8, 24.1, 25.1, 25.2, 24.2, 22.1, 20.0, 18.0, 16.0,14.0, 12.0, 10.0, 8.0, 6.1, 4.2, 3.0, 1.3/
DATA YDK/ 8.8, 7.6, 7.1, 7.4, 8.0, 8.9, 9.6, 9.9, 9.4,9.7, 12.0, 14.0, 16.1, 17.0, 17.0, 16.0, 13.9, 13.1,
13.2, 12.3, 11.5, 11.5, 11.5, 11.2, 10.5, 9.0, 8.0, 7.0,5.1, 3.6, 1.9, 1.1, 0.9, 0.7, 0.8, 1.0, 1.0, 1.2, 1.8,2.1, 2.9, 4.1, 6.0/
SET F ILL A R EA INDEX(1)
F ILL A R EA(43, XDK, YDK)
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Above code segment w ill produces theoutput given belo w
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SET F ILL A R EA INDEX(2) SET F ILL A R EA INDEX(3)
FI LLAREA INDE X() can be used to definethe fill pattern of the fill area
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TextGKS has a text primitive w hich is used toplace a String
F unction : TEXT(X, Y, ST R ING) (X, Y) is the text position ST R ING is a string of characters
E x: TEXT(6, 3, 'A Character String')
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Text Attributes -HEIGHT
The character height attributedetermines the height of the
characters in the string
Since a character in a font w ill have a
designed aspect ratio, the characterheight also determines the characterw idth.
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The character height is set by thefunction SET CHA R ACTE R HEIGHT(H)
w here H is the character height
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SET CHA R ACTE R HEIGHT(1)
TEXT(-2, 11. 'Character Height 1')
SET CHAR
ACTER
HEIGHT(2)TEXT( -2. 5, 'Character Height 2')
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Text Attributes - C HARA C TER UP VE C TOR
O ne of the most important text attributeMain purpose is to determine the
orientation of the characters It also sets a reference direction w hich isused in the determination of text pathand text alignmentSET CHA R ACTE R UP VECTO R (X, Y)X and Y are the offsets from the textposition of the up direction of the
characters
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SET CHA R ACTE R UP VECTO R (-1, 1)
TEXT(6, 3, 'A Character String')
SET CHA R ACTE R UP VECTO R (0, 1)SET TEXT PATH(DOWN)
TEXT(10, 17, 'G R AND HOTEL')
SET CHA R ACTE R UP VECTO R (1, 6)
SET TEXT PATH(DOWN)
TEXT(12, 16, 'HOTEL PISA')
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Acomplete GKS program
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Cell Arraymore specialized output primitiveallo w s images to be output
F unction : CELL A RR AY(XL, YL, X R , Y R , DIMX,
DIMY, SX, SY, DX, DY, CA)
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The t w o points in w orld coordinates(XL,YL) and (XR ,YR) specify the opposite
corners of a rectangular area w hich is to be divided into DX cells in theX direction and DY cells in the Y direction
Associated
with each cell is a colourspecified by the entry in the array C A(I,J)
w here I takes values from SX to (SX+ DX-1)and J takes values from SY to (SY+ DY-1)
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The corner cell at (XL,YL) correspondsto the array element C A(SX,SY) and theone at (X R ,YR) corresponds toCA(SX+DX-1 ,SY+DY-1)The entry C A(l,J) contains the position
in the w orkstation colour table w herethe RGB values of the colour arespecified
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The area of the pixel array and the colournumbers associated w ith the cells are
specified in the virtual side of GKSThe colour look-up table is specific to aparticular w orkstation
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It is quite easy to specify a cell arrayw hich can be vie w ed quite differentlyon t w o different w orkstations O ne could have a colour table
specifying the picture as a grey scale
image w hile a second specifies it as a pseudo
colour one.
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Group Members
UWU/CST/08/0001UWU/CST/08/0002UWU/CST/08/0003UWU/CST/08/0004UWU/CST/08/0005UWU/CST/08/0006UWU/CST/08/0007UWU/CST/08/0008UWU/CST/08/0009UWU/CST/08/0010
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D .H.G. M De SilvaG.W.S.S.K De Silva8910
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Thank You..!