# include <iostream.h>
 # include <graphics.h>
 # include    <conio.h>
 # include     <math.h>

 void show_screen( );

 void bresenham_line(constint,constint,constint,constint);


 int main( )
    {
       int driver=VGA;
       int mode=VGAHI;

       int x_1=0;
       int y_1=0;

       int x_2=0;
       int y_2=0;

       do
      {
         show_screen( );

         gotoxy(8,10);
         cout<<"Coordinates of Point-I (x1,y1) :";

         gotoxy(8,11);
         cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

         gotoxy(12,13);
         cout<<"Enter the value of x1 = ";
         cin>>x_1;

         gotoxy(12,14);
         cout<<"Enter the value of y1 = ";
         cin>>y_1;

         gotoxy(8,18);
         cout<<"Coordinates of Point-II (x2,y2) :";

         gotoxy(8,19);
         cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

         gotoxy(12,21);
         cout<<"Enter the value of x2 = ";
         cin>>x_2;

         gotoxy(12,22);
         cout<<"Enter the value of y2 = ";
         cin>>y_2;

         initgraph(&driver,&mode,"..\\Bgi");

         setcolor(15);
           bresenham_line(x_1,y_1,x_2,y_2);

         setcolor(15);
           outtextxy(110,460,"Press <Enter> to continue or any other key to exit.");

         int key=int(getch( ));

         if(key!=13)
        break;
      }
       while(1);

       return 0;
    }


 /*************************************************************************///--------------------------  bresenham_line( )  ------------------------///*************************************************************************/void bresenham_line(constint x_1,constint y_1,constint x_2,constint y_2)
    {
       int color=getcolor( );

       int x1=x_1;
       int y1=y_1;

       int x2=x_2;
       int y2=y_2;

       if(x_1>x_2)
      {
         x1=x_2;
         y1=y_2;

         x2=x_1;
         y2=y_1;
      }

       int dx=abs(x2-x1);
       int dy=abs(y2-y1);
       int two_dx=(2*dx);
       int two_dx_dy=(2*(dx-dy));
       int p=((2*dx)-dy);

       int x=x1;
       int y=y1;

       putpixel(x,y,color);

       while(y<y2)
      {
         y++;

         if(p<0)
        p+=two_dx;

         else
        {
           x++;
           p+=two_dx_dy;
        }

         putpixel(x,y,color);
      }
    }

 /*************************************************************************///--------------------------  show_screen( )  ---------------------------///*************************************************************************/void show_screen( )
    {
       restorecrtmode( );
       textmode(C4350);

       cprintf("\n********************************************************************************");
       cprintf("*************************-                              -***********************");
       cprintf("*------------------------- ");

       textbackground(1);
       cprintf(" Bresenham's Line Algorithm ");
       textbackground(8);

       cprintf(" -----------------------*");
       cprintf("*-***********************-                              -*********************-*");
       cprintf("*-****************************************************************************-*");

       for(int count=0;count<42;count++)
      cprintf("*-*                                                                          *-*");

       gotoxy(1,46);
       cprintf("*-****************************************************************************-*");
       cprintf("*------------------------------------------------------------------------------*");
       cprintf("********************************************************************************");

       gotoxy(8,40);
       cout<<"Note :";

       gotoxy(8,41);
       cout<<"ÍÍÍÍÍÍ";

       gotoxy(12,43);
       cout<<"The slope of the line should be negative and greater than 1.";

       gotoxy(1,2);
    }