/*Program to implement scan-fill*/
#include<graphics.h>
#include<stdio.h>
#include<conio.h>
#include<dos.h>

union REGS i,o;
struct pt
{
  int x,y;
};

float xl,xr,yt,yb;
int bc=0,xc,yc;

struct point
{
 float x,y;
};

float m;
int n=0,k,dy,dx,x,y,temp,a[20][2],xi[20];
float slope[20];

initmouse()
{
	i.x.ax=0;
	int86(0x33,&i,&o);
	return(o.x.ax);
}
showmouseptr()
{
	i.x.ax=1;
	int86(0x33,&i,&o);
	return(0);
}
hidemouseptr()
{
	i.x.ax=2;
	int86(0x33,&i,&o);
	return(0);
}
void getmousepos(int *button,int *x,int *y)
{
	i.x.ax=3;
	int86(0x33,&i,&o);
	*button=o.x.bx;
	*x=o.x.cx;
	*y=o.x.dx;
}


void scanfill()
{
 int ik,j;

 for(ik=0;ik<n;ik++)
	{
	 dy=a[ik+1][1]-a[ik][1];
	 dx=a[ik+1][0]-a[ik][0];
	 if(dy==0) slope[ik]=1.0;
	 if(dx==0) slope[ik]=0.0;
	 if((dy!=0)&&(dx!=0))
	 {
		slope[ik]=(float) dx/dy;
	 }
   }

 for(y=0;y<480;y++)
  {
   k=0;
   for(ik=0;ik<n;ik++)
	 {
	  if( ((a[ik][1]<=y)&&(a[ik+1][1]>y))||((a[ik][1]>y)&&(a[ik+1][1]<=y)))
	 {
	  xi[k]=(int)(a[ik][0]+slope[ik]*(y-a[ik][1]));
	  k++;
	 }
	 }

  for(j=0;j<k-1;j++)   //- Arrange x-intersections in order
	 for(ik=0;ik<k-1;ik++)
	{
	 if(xi[ik]>xi[ik+1])
	   {
		temp=xi[ik];
		xi[ik]=xi[ik+1];
		xi[ik+1]=temp;
	   }
	}
  setcolor(15);
  for(ik=0;ik<k;ik+=2)
	 {
	  line(xi[ik],y,xi[ik+1]+1,y);
	  delay(10);
	 }

 }//for(y)
}

void main()
{
	int cou,i,gd=DETECT,gm,flag;
	struct point p[30],pout[30],z;
	initgraph(&gd,&gm,"");
	cleardevice();
	showmouseptr();
	while(bc!=2)    //poly
	{
		getmousepos(&bc,&xc,&yc);
		if(bc==1)
		{
			p[n].x=xc;
			p[n].y=yc;
			n++;
			hidemouseptr();
			if(n>1)
			line(p[n-2].x,p[n-2].y,xc,yc);
			showmouseptr();
			delay(200);
		}
	}

	p[n]=p[0];
	hidemouseptr();
	line(p[n-1].x,p[n-1].y,p[n].x,p[n].y);
	showmouseptr();
	getmousepos(&bc,&xc,&yc);

	//flag=1;
	bc=0;
	hidemouseptr();
	cleardevice();
	for(i=0;i<n;i++)
	line(p[i].x,p[i].y,p[i+1].x,p[i+1].y);
	for(i=0;i<=n;i++)
	{
		a[i][0]=p[i].x;
		a[i][1]=p[i].y;
	}
	getch();
	getch();
	scanfill();
	getch();
}