#include<stdio.h>
#include<graphics.h>

/*
void putpixel(int x,int y,int v)
{
printf(" %6d %6d  ",x,y);
getch();
v=v;
}
*/
#define line(a,b,c,d) lin(320+(a),240-(b),320+(c),240-(d))

void swap(int *x1,int *x2,int *y1,int *y2)
{ int t;
t=*x1;*x1=*x2;*x2=t;
t=*y1;*y1=*y2;*y2=t;
}

void lin(int x1,int y1,int x2,int y2)
{
double slope;
int d,cas,a,b,
 incxg[]={ 1, 0, 1, 1},
 incyg[]={ 1, 1, 0,-1},
 incxl[]={ 1, 1, 1, 0},
 incyl[]={ 0, 1,-1,-1},

starta[]={ 2, 1, 2, 1},
startb[]={ 1, 2,-1,-2},

 incag[]={ 2, 0, 2, 2},
 incbg[]={ 2, 2, 0,-2},
 incal[]={ 2, 2, 2, 0},
 incbl[]={ 0, 2,-2,-2}
;




if(x1>x2) swap(&x1,&x2,&y1,&y2);


if(!(x2-x1))  x2++; //vertical lines are also approximated
//note that in our LAB question, the user can't enter INF.

slope=1.0*(y2-y1)/(x2-x1);

a=y2-y1;
b=x1-x2;

if(slope>=0 && slope<1)  		cas=0;
if(slope>=1)		 		cas=1;
if(slope>=-1 && slope<0) 		cas=2;
if(slope<-1) 				cas=3;

d = starta[cas]*a + startb[cas]*b;

while(x1<=x2)
{
 putpixel(x1,y1,WHITE);

 if(d>0) { x1+=incxg[cas];
	   y1+=incyg[cas];
	   d+=incag[cas]*a + incbg[cas]*b;
	 }
 else	 { x1+=incxl[cas];
	   y1+=incyl[cas];
	   d+=incal[cas]*a + incbl[cas]*b;
	 }
}

//getch();
}

void linethick(int x1,int y1,int x2,int y2,int th)
{
double sl=1.0*(y2-y1)/(x2-x1);
int i;

if(!sl) { for(i=1;i<=th;i++)
	  { line(x1,y1,x2,y2);
	    y1--; y2--;
	  }
	}
else    { for(i=1;i<=th;i++)
	  { line(x1,y1,x2,y2);
	    x1++; x2++; //y2=sl*(y1-x1)+x2;
	  }
	}
}


void polyline(int *x,int *y,int cnt,int thick)
{
int i;

if(cnt==1) { putpixel(x[0],y[0],WHITE); return; }

for(i=0;i<cnt-1;i++)
 linethick(x[i],y[i],x[i+1],y[i+1],thick);
}




main()
{
int gd=DETECT,gm,i,x1,y1,x2,y2,x[100],y[100],cnt;
double sl;
int th,a,b,c,d;

int ch;
printf("1) Line demo 2) Slope Demo 3) Polyline demo\n");
scanf("%d",&ch);

initgraph(&gd,&gm,"c:\\tcpp30\\bgi");




if(ch==1)
{
printf("Enter co-ordinates and thickness:");
while(scanf("%d%d%d%d%d",&x1,&y1,&x2,&y2,&th)==5)
 linethick(x1,y1,x2,y2,th);
}


else if(ch==2)
{
printf("Enter slope and thickness:");

while(scanf("%lf%d",&sl,&th)==2)
{

a=b=0;
if(!sl) { c=100; d=0;
	  for(i=1;i<=th;i++)
	  { line(a,b,c,d);
	    b--; d--;
	  }
	}
else    { c=100; d=sl*c;

	  for(i=1;i<=th;i++)
	  { line(a,b,c,d);
	    a++; c++; // d=sl*(c-a)+b;
	  }
	}
}
}

else if(ch==3)
{
printf("Enter the thickness:");
scanf("%d",&th);
printf("Enter number of points:");
scanf("%d",&cnt);
printf("Enter the points:");
for(i=0;i<cnt;i++)
 scanf("%d%d",&x[i],&y[i]);

polyline(x,y,cnt,th);
}
/*
//draw some lines in the top half

line(0,0,200,0);    //slope = 0
line(0,0,200,100);  //slope = 0.5
line(0,0,200,200);  //slope = 1
line(0,0,100,200);  //slope = 2
line(0,0,0,200);    //slope = INF
line(0,0,-100,200); //slope = -2
line(0,0,-200,200); //slope = -1
line(0,0,-200,100); //slope = -0.5
line(0,0,-200,0);   //back to 0

//draw in bottom half
line(0,0,200,-100);  //slope = -0.5
line(0,0,200,-200);  //slope = -1
line(0,0,100,-200);  //slope = -2
line(0,0,0,-200);    //slope = -INF
line(0,0,-100,-200); //slope = +2
line(0,0,-200,-200); //slope = +1
line(0,0,-200,-100); //slope = +0.5
*/



return 0;
}