Java Reference
In-Depth Information
Transformations
Oneofthemostpowerfulfeaturesofvectorgraphicsisthepossibilityof
transforminganimagebymanipulatingitscoordinatepoints.Supposeyou
createarectangular-shapedpolygondefinedbythe
x
-and
y
-coordinatesof
itsfourscreenpoints.Ifyouaddaconstantvaluetoeachofthe
x
coordi-
natesofthisimage,theresultisarectangletranslatedalongthe
x
-axisby
theamountaddedtoeachcoordinatepoint.Bythesametoken,youcan
translateavectorimagetoanydesiredscreenlocationbyaddingorsub-
tractingaconstantvaluetoeachofits
x
and
y
coordinates.
Figure27-2
showsthetranslationofarectangularpolygonbyaddinga
constanttoitsxandycoordinates.
y
x=7,y=6
x=1,y=4
x
Figure27-2TranslationofaPolygon
In
Figure27-2
therectangleinsolidlinesistranslatedtothepositionof
the rectangle in dashed lines by manipulating its coordinate points. In
this case a value of 6 was added to the
x
coordinate of each point and a
value of 2 to each of the
y
coordinates.
Other geometrical transformations that can be performed on vector
images are scaling and rotation. In scaling each coordinate point is multi-
plied by a scaling factor, which can be different for each coordinate
plane. In the rotation transformation the vector-based object is made to
move along a circular arc by applying a trigonometric function to each co-
ordinate point. Objects can be made to appear larger or smaller, can be
