#include<stdio.h>
#include<graphics.h>
#include<conio.h>
struct line_clip
{
 int p1x,p2x,p1y,p2y;
 };
int winmaxx,winmaxy,winminx,winminy;
int lineclip(float,float,float *,float *);
void clipline(struct line_clip *);

void main()
{
 int gd=DETECT,gm,i,j;
 struct line_clip p[10];
 printf("\nEnter the no.of lines");
 scanf("%d",&j);
 printf("Enter the window co-ordinates");
 scanf("%d %d %d %d",&winminx,&winminy,&winmaxx,&winmaxy);
 printf("Enter the co-ordinates for the lines");
 for(i=0;i<j;i++)
  scanf("%d%d%d%d",&p[i].p1x,&p[i].p1y,&p[i].p2x,&p[i].p2y);
 initgraph(&gd,&gm,"s:\\tc\\bgi");
 printf("Diagram before clipping");
 rectangle(winmaxx,winmaxy,winminx,winminy);
 for(i=0;i<j;i++)
  line(p[i].p1x,p[i].p1y,p[i].p2x,p[i].p2y);
 getch();
 cleardevice();
 rectangle(winmaxx,winmaxy,winminx,winminy);
 printf("Diagram after clipping");
 for(i=0;i<j;i++)
  clipline(&p[i]);
 getch();
 closegraph();
}

int lineclip(float p,float q,float *a1,float *a2)
{
 float r;
 if (p<0.0)
 {
  r=q/p;
  if (r>*a2) return(0);
  else if (r>*a1) *a1=r;
 }
 else
  if (p>0.0)
  {
   r=q/p;
   if (r<*a1) return(0);
   else if (r<*a2) *a2=r;
  }
  else
   if (q<0.0) return(0);
 return(1);
}


void clipline(struct line_clip *pp)
{
 float a1=0.0; float a2=1.0;
 float dx=pp->p2x - pp->p1x;
 float dy;
 if (lineclip(-dx,pp->p1x - winminx,&a1,&a2))
 if (lineclip(dx,winmaxx - pp->p1x,&a1,&a2))
 {
  dy=pp->p2y - pp->p1y;
  if (lineclip(-dy,pp->p1y - winminy,&a1,&a2))
  if (lineclip(dy,winmaxy - pp->p1y,&a1,&a2))
  {
   if(a1>0.0)
   {
    pp->p1x=(int)(pp->p1x + a1*dx);
    pp->p1y=(int)(pp->p1y + a1*dy);
   }
   if (a2<1.0)
   {
    pp->p2x=(int)(pp->p1x+a2*dx);
    pp->p2y=(int)(pp->p1y+a2*dy);
   }
  }
 }
 line(pp->p1x,pp->p1y,pp->p2x,pp->p2y);
}

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