//MIDPOINT SUBDIVISION LINE CLIPPING
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<dos.h>
#include<math.h>
#include<graphics.h>
typedef struct coordinate
{
int x,y;
char code[4];
}PT;
void drawwindow();
void drawline (PT p1,PT p2,int cl);
PT setcode(PT p);
int visibility (PT p1,PT p2);
PT resetendpt (PT p1,PT p2);
main()
{
int gd=DETECT, gm,v;
PT p1,p2,ptemp;
initgraph(&gd,&gm,"C:\\TC\\BGI ");
cleardevice();
printf("\n\n\t\tENTER END-POINT 1 (x,y): ");
scanf("%d,%d",&p1.x,&p1.y);
printf("\n\n\t\tENTER END-POINT 2 (x,y): ");
scanf("%d,%d",&p2.x,&p2.y);
cleardevice();
drawwindow();
getch();
drawline(p1,p2,15);
getch();
cleardevice();
drawwindow();
midsub(p1,p2);
getch();
closegraph();
return(0);
}
midsub(PT p1,PT p2)
{
PT mid;
int v;
p1=setcode(p1);
p2=setcode(p2);
v=visibility(p1,p2);
switch(v)
{
case 0: /* Line conpletely visible */
drawline(p1,p2,15);
break;
case 1: /* Line completely invisible */
break;
case 2: /* line partly visible */
mid.x = p1.x + (p2.x-p1.x)/2;
mid.y = p1.y + (p2.y-p1.y)/2;
midsub(p1,mid);
mid.x = mid.x+1;
mid.y = mid.y+1;
midsub(mid,p2);
break;
}
}
void drawwindow()
{
setcolor(RED);
line(150,100,450,100);
line(450,100,450,400);
line(450,400,150,400);
line(150,400,150,100);
}
void drawline (PT p1,PT p2,int cl)
{
setcolor(cl);
line(p1.x,p1.y,p2.x,p2.y);
}
PT setcode(PT p)
{
PT ptemp;
if(p.y<=100)
ptemp.code[0]='1'; /* TOP */
else
ptemp.code[0]='0';
if(p.y>=400)
ptemp.code[1]='1'; /* BOTTOM */
else
ptemp.code[1]='0';
if (p.x>=450)
ptemp.code[2]='1'; /* RIGHT */
else
ptemp.code[2]='0';
if (p.x<=150) /* LEFT */
ptemp.code[3]='1';
else
ptemp.code[3]='0';
ptemp.x=p.x;
ptemp.y=p.y;
return(ptemp);
}
int visibility (PT p1,PT p2)
{
int i,flag=0;
for(i=0;i<4;i++)
{
if((p1.code[i]!='0')||(p2.code[i]!='0'))
flag=1;
}
if(flag==0)
return(0);
for(i=0;i<4;i++)
{
if((p1.code[i]==p2.code[i]) &&(p1.code[i]=='1'))
flag=0;
}
if(flag==0)
return(1);
return(2);
}
SAMPLE OUTPUT:
