Program to show the implementation of Window-to-Viewport Coordinate Transformaton

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


 class RectangularCoordinates
    {
       public:
      float x_min;
      float y_min;
      float x_max;
      float y_max;

      RectangularCoordinates(const float x1,const float y1,
                          const float x2,const float y2)
         {
        x_min=x1;
        y_min=y1;
        x_max=x2;
        y_max=y2;
         }
    };


 void show_screen( );

 void apply_window_to_viewport_coordinate_transformation(
                    const RectangularCoordinates,
                     const RectangularCoordinates,
                                   int &,int &);

 void Rectangle(const int,const int,const int,const int);
 void Line(const int,const int,const int,const int);

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

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

       show_screen( );

       setcolor(15);
     Line(90,150,90,390);
     Line(50,350,320,350);

     Line(400,150,400,390);
     Line(360,350,580,350);

       RectangularCoordinates WC(130,180,290,300);
       RectangularCoordinates VC(440,230,550,300);

       setcolor(15);
     Line(90,180,95,180);
     Line(90,300,95,300);

     Line(130,345,130,350);
     Line(290,345,290,350);

     Line(400,230,405,230);
     Line(400,300,405,300);

     Line(440,345,440,350);
     Line(550,345,550,350);

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

       setcolor(15);
     settextstyle(0,0,1);
       outtextxy(50,175,\"YW\");
       outtextxy(50,295,\"YW\");
       outtextxy(110,360,\"XW\");
       outtextxy(280,360,\"XW\");

       outtextxy(360,225,\"YV\");
       outtextxy(360,295,\"YV\");
       outtextxy(420,360,\"XV\");
       outtextxy(530,360,\"XV\");

       outtextxy(182,170,\"Window\");
       outtextxy(140,390,\"World Coordinates\");

       outtextxy(462,220,\"Viewport\");
       outtextxy(420,390,\"Device Coordinates\");

     settextstyle(2,0,4);
       outtextxy(67,175,\"min\");
       outtextxy(67,295,\"max\");
       outtextxy(127,360,\"min\");
       outtextxy(297,360,\"max\");

       outtextxy(377,225,\"min\");
       outtextxy(377,295,\"max\");
       outtextxy(437,360,\"min\");
       outtextxy(547,360,\"max\");

       int x=210;
       int y=240;

       putpixel(x,y,15);

       setcolor(15);
       settextstyle(2,0,4);
     outtextxy((x-20),(y+3),\"(XW,YW)\");

       char Key=NULL;

       do
      {
         Key=getch( );
      }
       while(Key!=\'T\' && Key!=\'t\');

       settextstyle(0,0,1);
     setcolor(0);
       outtextxy(36,450,\"  Press \'T\' to see the Window-to-Viewport Coordinate Transformation.  \");

    setcolor(15);
       outtextxy(38,450,\"-----------------------                          ---------------------\");

     setcolor(12);
       outtextxy(222,450,\"  Press any Key to exit.  \");

       apply_window_to_viewport_coordinate_transformation(WC,VC,x,y);

       putpixel(x,y,14);

       setcolor(15);
       settextstyle(2,0,4);
     outtextxy((x-20),(y+3),\"(XV,YV)\");

       getch( );
       return 0;
    }



 //-----  apply_window_to_viewport_coordinate_transformation( )  ---------//


 void apply_window_to_viewport_coordinate_transformation(
                     const RectangularCoordinates wc,
                     const RectangularCoordinates vc,
                                   int &x,int &y)
    {
       float Sx=((vc.x_max-vc.x_min)/(wc.x_max-wc.x_min));
       float Sy=((vc.y_max-vc.y_min)/(wc.y_max-wc.y_min));
       float Tx=vc.x_min;
       float Ty=vc.y_min;

       x=(Tx+(Sx*(x-wc.x_min)));
       y=(Ty+(Sy*(y-wc.y_min)));
    }


 //---------------------------  Rectangle( )  ----------------------------//


 void Rectangle(const int x_1,const int y_1,const int x_2,const int 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(const int x_1,const int y_1,const int x_2,const int 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(130,26,500,38);

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

     setcolor(11);
       outtextxy(140,29,\"Window-to-Viewport Coordinate Transformation\");

     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(36,450,\"  Press \'T\' to see the Window-to-Viewport Coordinate Transformation.  \");
    }