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


 class LineCoordinates
    {
       public:
      float x_1;
      float y_1;
      float x_2;
      float y_2;

      LineCoordinates(constfloat x1,constfloat y1,
                          constfloat x2,constfloat y2)
         {
        x_1=x1;
        y_1=y1;
        x_2=x2;
        y_2=y2;
         }
    };

 /*************************************************************************///-------------------------  WindowCoordinates  -------------------------///*************************************************************************/class WindowCoordinates
    {
       public:
      float x_min;
      float y_min;
      float x_max;
      float y_max;

      WindowCoordinates(constfloat x1,constfloat y1,
                          constfloat x2,constfloat y2)
         {
        x_min=x1;
        y_min=y1;
        x_max=x2;
        y_max=y2;
         }
    };


 void show_screen( );

 constint clip_line(const WindowCoordinates,LineCoordinates&);
 constint check_line(constfloat,constfloat,float&,float&);

 void Rectangle(constint,constint,constint,constint);
 void Line(constint,constint,constint,constint);


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

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

       show_screen( );

       WindowCoordinates WC(180,140,470,340);

       setcolor(15);
     Rectangle(WC.x_min,WC.y_min,WC.x_max,WC.y_max);

       LineCoordinates LC_1(150,160,120,320);
       LineCoordinates LC_2(250,150,200,200);
       LineCoordinates LC_3(160,200,490,260);
       LineCoordinates LC_4(300,300,400,380);
       LineCoordinates LC_5(550,300,450,400);
       LineCoordinates LC_6(440,110,400,370);

       setcolor(7);
     Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);
     Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);
     Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);
     Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);
     Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);
     Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);

       char Key=NULL;

       do
      {
         Key=getch( );
      }
       while(Key!='C' && Key!='c');

       settextstyle(0,0,1);
     setcolor(0);
       outtextxy(163,450,"  Press 'C' to see the Clipped Lines.  ");

    setcolor(15);
       outtextxy(163,450,"------                          -------");

     setcolor(12);
       outtextxy(213,450,"  Press any Key to exit.  ");

       setcolor(10);

       if(clip_line(WC,LC_1))
      Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);

       if(clip_line(WC,LC_2))
      Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);

       if(clip_line(WC,LC_3))
      Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);

       if(clip_line(WC,LC_4))
      Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);

       if(clip_line(WC,LC_5))
      Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);

       if(clip_line(WC,LC_6))
      Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);

       getch( );
       return 0;
    }

 /*************************************************************************///---------------------------  clip_line( )  ----------------------------///*************************************************************************/constint clip_line(const WindowCoordinates wc,LineCoordinates &lc)
    {
       float u_1=0;
       float u_2=1;

       float dx=(lc.x_2-lc.x_1);
       float dy=(lc.y_2-lc.y_1);

       float p1=(-dx);
       float p2=dx;
       float p3=(-dy);
       float p4=dy;

       float q1=(lc.x_1-wc.x_min);
       float q2=(wc.x_max-lc.x_1);
       float q3=(lc.y_1-wc.y_min);
       float q4=(wc.y_max-lc.y_1);

       if(check_line(p1,q1,u_1,u_2) && check_line(p2,q2,u_1,u_2) &&
             check_line(p3,q3,u_1,u_2) && check_line(p4,q4,u_1,u_2))
      {
         if(u_2<1)
        {
           lc.x_2=(lc.x_1+(u_2*dx));
           lc.y_2=(lc.y_1+(u_2*dy));
        }

         if(u_1>0)
        {
           lc.x_1+=(u_1*dx);
           lc.y_1+=(u_1*dy);
        }

         lc.x_1=(int)(lc.x_1+0.5);
         lc.y_1=(int)(lc.y_1+0.5);
         lc.x_2=(int)(lc.x_2+0.5);
         lc.y_2=(int)(lc.y_2+0.5);

         return 1;
      }

       return 0;
    }

 /*************************************************************************///------------------------------  check_line( )  ------------------------///*************************************************************************/constint check_line(constfloat p,constfloat q,float &u_1,float &u_2)
    {
       int flag=1;

       float r=(q/p);

       if(p<0)
      {
         if(r>u_2)
        flag=0;

         elseif(r>u_1)
        u_1=r;
      }

       elseif(p>0)
      {
         if(r<u_1)
        flag=0;

         elseif(r<u_2)
        u_2=r;
      }

       else
      {
         if(q<0)
        flag=0;
      }

       return flag;
    }

 /*************************************************************************///---------------------------  Rectangle( )  ----------------------------///*************************************************************************/void Rectangle(constint x_1,constint y_1,constint x_2,constint y_2)
    {
       Line(x_1,y_1,x_2,y_1);
       Line(x_2,y_1,x_2,y_2);
       Line(x_2,y_2,x_1,y_2);
       Line(x_1,y_2,x_1,y_1);
    }

 /*************************************************************************///--------------------------  Line( )  ------------------------///*************************************************************************/void 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 inc_dec=((y2>=y1)?1:-1);

       if(dx>dy)
      {
         int two_dy=(2*dy);
         int two_dy_dx=(2*(dy-dx));
         int p=((2*dy)-dx);

         int x=x1;
         int y=y1;

         putpixel(x,y,color);

         while(x<x2)
        {
           x++;

           if(p<0)
              p+=two_dy;

           else
              {
             y+=inc_dec;
             p+=two_dy_dx;
              }

           putpixel(x,y,color);
        }
      }

       else
      {
         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+=inc_dec;

           if(p<0)
              p+=two_dx;

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

           putpixel(x,y,color);
        }
      }
    }

 /*************************************************************************///--------------------------  show_screen( )  ---------------------------///*************************************************************************/void show_screen( )
    {
       setfillstyle(1,1);
     bar(165,26,470,38);

       settextstyle(0,0,1);
     setcolor(15);
       outtextxy(5,5,"******************************************************************************");
       outtextxy(5,17,"*-**************************************************************************-*");
       outtextxy(5,29,"*------------------                                        ------------------*");
       outtextxy(5,41,"*-**************************************************************************-*");
       outtextxy(5,53,"*-**************************************************************************-*");

     setcolor(11);
       outtextxy(174,29,"Liang-Barsky Line Clipping Algorithm");

     setcolor(15);

       for(int count=0;count<=30;count++)
          outtextxy(5,(65+(count*12)),"*-*                                                                        *-*");

       outtextxy(5,438,"*-**************************************************************************-*");
       outtextxy(5,450,"*-------------------                                       ------------------*");
       outtextxy(5,462,"******************************************************************************");

     setcolor(12);
       outtextxy(163,450,"  Press 'C' to see the Clipped Lines.  ");
    }