//Header Files
#include<constrea.h>
#include<graphics.h>
#include<stdlib.h>
//Clipping Coordinates
int ymin,ymax,xmin,xmax;
//point structure
struct point
{
int x,y;
point():x(0),y(0){}
};
//swap function
void swap(int &a,int &b)
{
    int rep=a;
	  a=b;
	  b=rep;
}
//check 4 bit code
int code(point p)
{
	int code = 0;
	if(p.x<xmin)
	code=(code|0x1); //for left
	if(p.x>xmax)
	code=(code|0x2); //for right
	if(p.y<ymin)
	code=(code|0x4); // for bottom
	if(p.y>ymax)
	code=(code|0x8); // for above
	return code;
}
//clip the line according to clipping window
void clipline(point p1,point p2)
{
int    draw=0;
float  slope;
int    code1,code2;

while(1)
{
code1=code(p1);
code2=code(p2);

	if(!(code1|code2))
	   {
	   draw = 1;
	   break;
	   }
	else if(code1&code2)
	   {
	   break;
	   }
	else
	   {
	   if(!code1)
	   {
	    swap(p1.x,p2.x);
	    swap(p1.y,p2.y);
	    swap(code1,code2);
	   }

	 if(p2.x!=p1.x)
	  {
	 slope=(float)(p2.y-p1.y)/(float)(p2.x-p1.x);
	  }

	 if(code1&0x1) //for left
	  {
	   p1.y=p1.y+(xmin-p1.x)*slope;
	   p1.x=xmin;
	  }
	  else if(code1&0x2)//for right
	  {
	   p1.y=p1.y+(xmax-p1.x)*slope;
	   p1.x=xmax;
	  }
	 else if(code1&0x4) // for bottom
	 {
	  if(p1.x != p2.x)
	   p1.x=p1.x+(ymin-p1.y)/slope;
	   p1.y=ymin;
	 }
	 if(code1&0x8) // for above
	 {
	  if(p1.x != p2.x)
	  p1.x=p1.x+(ymax-p1.y)/slope;
	  p1.y=ymax;
	 }
    }
  }
	if(draw)
line(p1.x,p1.y,p2.x,p2.y);
}
//Main Function
void main()
{

int d,m,i;

	detectgraph(&d,&m);
	initgraph(&d,&m,"f:\\tc\\bgi");

	cout<<"Enter Clipping Points:";
	cin>>xmin>>ymin>>xmax>>ymax;

rectangle(xmin,ymin,xmax,ymax);

point p1,p2;

randomize();

for(i=0;i<100;i++)
{
//point 1
p1.x=random(600);
p1.y=random(400);
//poing 2
p2.x=random(600);
p2.y=random(400);
//clip the line with respect to clipping window
clipline(p1,p2);
}

getch();
}
/****************************************************************/