MIDSUB.CPP

//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);
void midsub(PT,PT);
int visibility (PT p1,PT p2);
PT resetendpt (PT p1,PT p2);

int main()
{
	 int gd=DETECT, gm,v;
	 PT p1,p2,ptemp;                            \
	 initgraph(&gd,&gm,"C:\\Turboc3\\BGI ");
	 cleardevice();
	 
	 printf("\n\n\t\tENTER END-POINT 1 (x,y): ");
	 scanf("%d",&p1.x);
	 scanf("%d",&p1.y);
	 
	 printf("\n\n\t\tENTER END-POINT 2 (x,y): ");
	 scanf("%d",&p2.x);
	 scanf("%d",&p2.y);
	 
	 cleardevice();
	 drawwindow();
	 getch();
	 
	 drawline(p1,p2,15);
	 getch();
	 cleardevice();
	 
	 drawwindow();
	 midsub(p1,p2);
	 
	 getch();
	 closegraph();
	 return(0);
}


void 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++)//for trivial visible
	{
		if((p1.code[i]!='0')||(p2.code[i]!='0'))
		flag=1;
	}
	if(flag==0)
		return(0);
	for(i=0;i<4;i++)//for trivial invisible
	{
		if((p1.code[i]==p2.code[i]) &&(p1.code[i]=='1'))
		flag=0;
	}
	if(flag==0)
		return(1);
	return(2);
}