BRESENHAM’S ELLIPSE DRAWING ALGORITHM

#include
#include
#include
void main()
{
long d1,d2;
int i,gd,gm,x,y;
long rx,ry,rxsq,rysq,tworxsq,tworysq,dx,dy;
printf("\n enter the x radius of the ellipse:");
scanf("%ld",&rx);
printf("\n enter the y radius of the ellipse:");
scanf("%ld",&ry);
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"c:\\Tc\\BGI ");
rxsq=rx*rx;
rysq=ry*ry;
tworxsq=2*rxsq;
tworysq=2*rysq;
x=0;
y=ry;
d1=rysq-rxsq*ry+(0.25*rxsq);
dx=tworysq*x;
dy=tworxsq*y;
do
{
putpixel(200+x,200+y,15);
putpixel(200-x,200-y,15);
putpixel(200+x,200-y,15);
putpixel(200-x,200+y,15);
if(d1<0)
{
x=x+1;
y=y;
dx=dx+tworysq;
d1=d1+dx+rysq;
}
else
{
x=x+1;
y=y-1;
dx=dx+tworysq;
dy=dy-tworxsq;
d1=d1+dx-dy+rysq;
}
delay(5);
}
while(dxd2=rysq*(x+0.5)*(x+0.5)+rxsq*(y-1)*(y-1)-rxsq*rysq;
do
{
putpixel(200+x,200+y,15);
putpixel(200-x,200-y,15);
putpixel(200+x,200-y,15);
putpixel(200-x,200+y,15);
if(d2>0)
{
x=x;
y=y-1;
dy=dy-tworxsq;
d2=d2-dy+rxsq;
}
else
{
x=x+1;
y=y-1;
dy=dy-tworxsq;
dx=dx+tworysq;
d2=d2+dx-dy+rxsq;
}}
while(y>0);
getch();
closegraph();
}