Program to illustrate the implementation of Reflection Transformation about x-axix, y-axis and w.r.t origin

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

 void show_screen( );

 void apply_reflection_along_x_axis(const int,int []);
 void apply_reflection_along_y_axis(const int,int []);
 void apply_reflection_wrt_origin(const int,int []);
 void multiply_matrices(const int[3],const int[3][3],int[3]);

 void Polygon(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(320,100,320,400);

      Line(315,105,320,100);
      Line(320,100,325,105);

      Line(315,395,320,400);
      Line(320,400,325,395);

      Line(150,240,500,240);

      Line(150,240,155,235);
      Line(150,240,155,245);

      Line(500,240,495,235);
      Line(500,240,495,245);

       settextstyle(2,0,4);
     outtextxy(305,85,\"y-axis\");
     outtextxy(305,402,\"y\'-axis\");

     outtextxy(505,233,\"x-axis\");
     outtextxy(105,233,\"x\'-axis\");

     outtextxy(380,100,\"Original Object\");
     outtextxy(380,385,\"Reflection along x-axis\");
     outtextxy(135,100,\"Reflection along y-axis\");
     outtextxy(135,385,\"Reflection w.r.t origin\");

       int polygon_points[8]={ 350,200, 380,150, 470,200, 350,200 };
       int x_polygon[8]={ 350,200, 380,150, 470,200, 350,200 };
       int y_polygon[8]={ 350,200, 380,150, 470,200, 350,200 };
       int origin_polygon[8]={ 350,200, 380,150, 470,200, 350,200 };

       setcolor(15);
     Polygon(4,polygon_points);

       apply_reflection_along_x_axis(4,x_polygon);

       setcolor(12);
     Polygon(4,x_polygon);

       apply_reflection_along_y_axis(4,y_polygon);

       setcolor(14);
     Polygon(4,y_polygon);

       apply_reflection_wrt_origin(4,origin_polygon);

       setcolor(10);
     Polygon(4,origin_polygon);

       getch( );
       return 0;
    }


 //------------------  apply_reflection_along_x_axis( )  -----------------//


 void apply_reflection_along_x_axis(const int n,int coordinates[])
    {
       for(int count=0;count<n;count++)
      {
         int matrix_a[3]={coordinates[(count*2)],
                         coordinates[((count*2)+1)],1};
         int matrix_b[3][3]={ {1,0,0} , {0,-1,0} ,{ 0,0,1} };
         int matrix_c[3]={0};

         multiply_matrices(matrix_a,matrix_b,matrix_c);

         coordinates[(count*2)]=matrix_c[0];
         coordinates[((count*2)+1)]=(480+matrix_c[1]);
      }
    }


 //------------------  apply_reflection_along_y_axis( )  -----------------//


 void apply_reflection_along_y_axis(const int n,int coordinates[])
    {
       for(int count=0;count<n;count++)
      {
         int matrix_a[3]={coordinates[(count*2)],
                         coordinates[((count*2)+1)],1};
         int matrix_b[3][3]={ {-1,0,0} , {0,1,0} ,{ 0,0,1} };
         int matrix_c[3]={0};

         multiply_matrices(matrix_a,matrix_b,matrix_c);

         coordinates[(count*2)]=(640+matrix_c[0]);
         coordinates[((count*2)+1)]=matrix_c[1];
      }
    }


 //------------------  apply_reflection_wrt_origin( )  -------------------//


 void apply_reflection_wrt_origin(const int n,int coordinates[])
    {
       for(int count=0;count<n;count++)
      {
         int matrix_a[3]={coordinates[(count*2)],
                         coordinates[((count*2)+1)],1};
         int matrix_b[3][3]={ {-1,0,0} , {0,-1,0} ,{ 0,0,1} };
         int matrix_c[3]={0};

         multiply_matrices(matrix_a,matrix_b,matrix_c);

         coordinates[(count*2)]=(640+matrix_c[0]);
         coordinates[((count*2)+1)]=(480+matrix_c[1]);
      }
    }

 /************************************************************************/
 //----------------------  multiply_matrices( )  ------------------------//
 /************************************************************************/

 void multiply_matrices(const int matrix_1[3],
                  const int matrix_2[3][3],int matrix_3[3])
    {
       for(int count_1=0;count_1<3;count_1++)
      {
         for(int count_2=0;count_2<3;count_2++)
        matrix_3[count_1]+=
               (matrix_1[count_2]*matrix_2[count_2][count_1]);
      }
    }


 //-----------------------------  Polygon( )  ----------------------------//


 void Polygon(const int n,const int coordinates[])
    {
       if(n>=2)
      {
         Line(coordinates[0],coordinates[1],
                         coordinates[2],coordinates[3]);

         for(int count=1;count<(n-1);count++)
        Line(coordinates[(count*2)],coordinates[((count*2)+1)],
                        coordinates[((count+1)*2)],
                        coordinates[(((count+1)*2)+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(208,26,430,38);

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

     setcolor(11);
       outtextxy(218,29,\"Reflection 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(229,450,\"Press any Key to exit.\");
    }