ELLIPSE - MID POINT

                                    

Program : 

/*<applet code = ellipse height = 400 width = 400>

</applet>*/

import java.awt.*;

import java.applet.*;

import java.awt.event.*;

public class ellipse extends Applet implements ActionListener {

float x,y,xc,yc,rx,ry,p1,p2;

Label l1 = new Label("semi major axis = ");

Label l2 = new Label("semi minor axis = ");

Label l3 = new Label("x = ");

Label l4 = new Label("y = ");

TextField t1 = new TextField(3);

TextField t2 = new TextField(3);

TextField t3 = new TextField(3);

TextField t4 = new TextField(3);

Button bw = new Button("DRAW");

public void init(){

add(l1);

add(t1);

add(l2);

add(t2);

add(l3);

add(t3);

add(l4);

add(t4);

add(bw);

bw.addActionListener(this);

}

public void  paint(Graphics g)

{

rx=Integer.parseInt(t1.getText());

ry=Integer.parseInt(t2.getText());

xc=Integer.parseInt(t3.getText());

yc=Integer.parseInt(t4.getText());

x=0;

y=ry;

p1=(ry*ry)-(rx*rx*y)+(rx*rx/4);

do{

g.drawString(".",Math.round(xc-x),Math.round(yc+y));

g.drawString(".",Math.round(xc-x),Math.round(yc-y));

g.drawString(".",Math.round(xc+x),Math.round(yc+y));

g.drawString(".",Math.round(xc+x),Math.round(yc-y));

x++;

if(p1<0)

p1=p1+(2*ry*ry*x)+(ry*ry);

else

{

y-=1;

p1=p1+(2*ry*ry*x)-(2*rx*rx*y)+(ry*ry);

}

}

while((2*ry*ry*x)<(2*rx*rx*y));

p2= (ry*ry*(x+1/2)*(x+1/2))+(rx*rx*(y-1)*(y-1))-(ry*ry*rx*rx);

while(y>0)

{

g.drawString(".",Math.round(xc-x),Math.round(yc+y));

g.drawString(".",Math.round(xc-x),Math.round(yc-y));

g.drawString(".",Math.round(xc+x),Math.round(yc+y));

g.drawString(".",Math.round(xc+x),Math.round(yc-y));

y--;

if(p2>0)

p2 = p2-(2*rx*rx*y)+(ry*ry);

else{

x+=1;

p2 = p2=(2*ry*ry*x)+(2*rx*rx*y)+(ry*ry);

}

}

public void actionPerformed(ActionEvent aw)

{ 

repaint();

}

}