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Listing 27 . Source code for the program named PointLine03.
/*PointLine03.java
Copyright 2008, R.G.BaldwinRevised 02/03/08
This program illustrates the use of draw methods thatwere added to the GM2D02 game-math library to produce
visual manifestations of point, line, and vector objectsinstantiated from classes in the game-math library
named GM2D02.The program also illustrates drawing on off-screen images
and then copying those images to a Canvas object in anoverridden paint method.
Tested using JDK 1.6 under WinXP.*********************************************************/
import java.awt.*;import javax.swing.*;
class PointLine03{public static void main(String[] args){GUI guiObj = new GUI();
}//end main}//end controlling class PointLine03
//======================================================//class GUI extends JFrame{
//Specify the horizontal and vertical size of a JFrame// object.
int hSize = 400;int vSize = 200;
Image osiA;//one off-screen imageImage osiB;//another off-screen image
int osiWidth;//off-screen image widthint osiHeight;//off-screen image height
MyCanvas myCanvas;//a subclass of CanvasGUI(){//constructor//Set JFrame size, title, and close operation.
setSize(hSize,vSize);setTitle("Copyright 2008,R.G.Baldwin");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//Create a new drawing canvas and add it to the// center of the JFrame.
myCanvas = new MyCanvas();this.getContentPane().add(myCanvas);//This object must be visible before you can get an
// off-screen image. It must also be visible before// you can compute the size of the canvas.
setVisible(true);osiWidth = myCanvas.getWidth()/2;
osiHeight = myCanvas.getHeight();//Create two off-screen images and get a graphics
// context on each.osiA = createImage(osiWidth,osiHeight);
Graphics2D g2Da = (Graphics2D)(osiA.getGraphics());osiB = createImage(osiWidth,osiHeight);Graphics2D g2Db = (Graphics2D)(osiB.getGraphics());//Draw some points, lines, and vectors on the two
// off-screen images.drawOffscreen(g2Da,g2Db);
//Cause the overridden paint method belonging to// myCanvas to be executed.
myCanvas.repaint();}//end constructor
//----------------------------------------------------////The purpose of this method is to define points, lines,// and vectors and then to cause a visual manifestation
// of some of the points, lines, and vectors to be// drawn onto two separate off-screen images.
void drawOffscreen(Graphics2D g2Da,Graphics2D g2Db){//Draw a label on each off-screen image.g2Da.drawString("Off-screen image A",
osiWidth/8,osiHeight/8);
g2Db.drawString("Off-screen image B",osiWidth/8,
osiHeight/8);//Define four lines that can be used to draw borders// on each of the off-screen images.
//First define four points that will be used to define// the ends of the four lines.
GM2D02.Point upperLeftPoint = new GM2D02.Point(new GM2D02.ColMatrix(1.0,1.0));
GM2D02.Point upperRightPoint = new GM2D02.Point(new GM2D02.ColMatrix(osiWidth-1,1.0));
GM2D02.Point lowerRightPoint = new GM2D02.Point(new GM2D02.ColMatrix(osiWidth-1,osiHeight-1));
GM2D02.Point lowerLeftPoint = new GM2D02.Point(new GM2D02.ColMatrix(1.0,osiHeight-1));//Now define the four lines based on the endpoints..
GM2D02.Line top = new GM2D02.Line(upperLeftPoint,upperRightPoint);
GM2D02.Line rightSide = new GM2D02.Line(upperRightPoint,
lowerRightPoint);GM2D02.Line bottom = new GM2D02.Line(lowerLeftPoint,
lowerRightPoint);GM2D02.Line leftSide = new GM2D02.Line(upperLeftPoint,
lowerLeftPoint);//Now draw a visual manifestation of each line// on g2Da.
top.draw(g2Da);rightSide.draw(g2Da);
bottom.draw(g2Da);leftSide.draw(g2Da);//Now draw a visual manifestation of each of the same
// four lines on g2Dbtop.draw(g2Db);
rightSide.draw(g2Db);bottom.draw(g2Db);
leftSide.draw(g2Db);//Translate the origin of g2Da to the center of the// off-screen image.
g2Da.translate(osiWidth/2.0,osiHeight/2.0);//Define a point at the new origin and draw a visual// manifestation of the point.
GM2D02.Point origin = new GM2D02.Point(new GM2D02.ColMatrix(0.0,0.0));
origin.draw(g2Da);//Define six points that define the vertices of a// hexagon that is symmetrically located relative to
// the origin. Begin at the right and move clockwise// around the origin.
//First define three constants to make it easier to// write the code.
final double aVal = osiWidth/4.0*0.5;final double bVal = osiWidth/4.0*0.866;
final double cVal = osiWidth/4.0;//Now define the points.
GM2D02.Point point0 = new GM2D02.Point(new GM2D02.ColMatrix(cVal,0.0));
GM2D02.Point point1 = new GM2D02.Point(new GM2D02.ColMatrix(aVal,bVal));
GM2D02.Point point2 = new GM2D02.Point(new GM2D02.ColMatrix(-aVal,bVal));
GM2D02.Point point3 = new GM2D02.Point(new GM2D02.ColMatrix(-cVal,0.0));
GM2D02.Point point4 = new GM2D02.Point(new GM2D02.ColMatrix(-aVal,-bVal));
GM2D02.Point point5 = new GM2D02.Point(new GM2D02.ColMatrix(aVal,-bVal));//Now draw a visual manifestation of each of the six
// points on g2Da.point0.draw(g2Da);
point1.draw(g2Da);point2.draw(g2Da);
point3.draw(g2Da);point4.draw(g2Da);
point5.draw(g2Da);//Now define six lines using the six points taken in// pairs to define the endpoints of the lines.
GM2D02.Line line01 = new GM2D02.Line(point0,point1);GM2D02.Line line12 = new GM2D02.Line(point1,point2);
GM2D02.Line line23 = new GM2D02.Line(point2,point3);GM2D02.Line line34 = new GM2D02.Line(point3,point4);
GM2D02.Line line45 = new GM2D02.Line(point4,point5);GM2D02.Line line50 = new GM2D02.Line(point5,point0);
//Now draw a visual manifestation of each line// on g2Da.
line01.draw(g2Da);line12.draw(g2Da);
line23.draw(g2Da);line34.draw(g2Da);
line45.draw(g2Da);line50.draw(g2Da);//Now define three vectors and draw visual
// manifestations of the vectors on g2Db.GM2D02.Vector vecA = new GM2D02.Vector(
new GM2D02.ColMatrix(50,100));GM2D02.Vector vecB = new GM2D02.Vector(
new GM2D02.ColMatrix(75,25));GM2D02.Vector vecC = new GM2D02.Vector(
new GM2D02.ColMatrix(125,125));//Draw vecA in red with its tail at the origin, which// is still at the upper-left corner of the g2Db
// off-screen imageg2Db.setColor(Color.RED);
vecA.draw(g2Db,new GM2D02.Point(new GM2D02.ColMatrix(0,0)));//Draw three visual manifestations of vecB. Cause
// the tail of vecB to coincide with the head of vecA// in one of the three visual manifestations. Make all
// three of them green.g2Db.setColor(Color.GREEN);
vecB.draw(g2Db,new GM2D02.Point(newGM2D02.ColMatrix(
vecA.getData(0),vecA.getData(1))));vecB.draw(g2Db,new GM2D02.Point(new GM2D02.ColMatrix(
vecA.getData(0)-10,vecA.getData(1)+15)));vecB.draw(g2Db,new GM2D02.Point(new GM2D02.ColMatrix(
vecA.getData(0)+10,vecA.getData(1)-60)));//Draw vecC in blue with its tail at the origin.
g2Db.setColor(Color.BLUE);vecC.draw(g2Db,new GM2D02.Point(
new GM2D02.ColMatrix(0,0)));}//end drawOffscreen
//====================================================////This is an inner class of the GUI class.
class MyCanvas extends Canvas{//Override the paint() method. This method will be
// called when the JFrame and the Canvas appear on the// screen or when the repaint method is called on the
// Canvas object.//The purpose of this method is to display the two
// off-screen images on the screen in a side-by-side// format.
public void paint(Graphics g){g.drawImage(osiA,0,0,this);
g.drawImage(osiB,this.getWidth()/2,0,this);}//end overridden paint()}//end inner class MyCanvas}//end class GUI
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