#include<math.h>
#include<graphics.h>
#define maxsize 3
#define max_pts 3
struct point {
			float x;
			float y;
		   }pts[3];
void set_identity_matrix(float a[3][3]);
void rotation_matrix(float rm[3][3],float);
void set_point_matrix(float pm[3][3], struct point);
void multiply_matrix(float[3][3],float[3][3]);
void scaling_matrix(float[3][3],float,float);
void translation_matrix(float[3][3],float,float);
void do_transformation(float,float,float,float,float,struct point*);

void main()
{
  struct point* p1;/* This stmt says that p1 can hold the address of  a variable of
				  type struct point */
  int i;int gd = DETECT; int gm = DETECT;
  clrscr();
  initgraph(&gd,&gm,"c:\\tc\\bgi");

  pts[0].x = 150; pts[1].x = 250; pts[2].x = 200;
  pts[0].y = 150; pts[1].y =  100; pts[2].y = 200;

  for( i = 0; i < max_pts-1; i++)
  {
	line(pts[i].x,pts[i].y,pts[i+1].x,pts[i+1].y);
  }
  line(pts[i].x,pts[i].y,pts[0].x,pts[0].y);
  getch();
  for( i = 0; i < max_pts; i++)
  {
	p1 = &pts[i];

	do_transformation(  180,  0.5,  0.5,-200,-200,p1);
	do_transformation(  0,  1,  1, 200, 200,p1);
  }
  for ( i = 0; i < max_pts-1; i++)
  {
	 line(pts[i].x,pts[i].y,pts[i+1].x,pts[i+1].y);
  }
  line(pts[i].x,pts[i].y,pts[0].x,pts[0].y);
  getch();


}





void do_transformation(float theta, float sx, float sy, float tx, float ty, struct point* p1)
{
   float tm[maxsize][maxsize],sm[maxsize][maxsize],rm[maxsize][maxsize],r[maxsize][maxsize],pm[maxsize][maxsize];

   set_identity_matrix(tm);
   set_identity_matrix(sm);
   set_identity_matrix(rm);
   set_identity_matrix(r);
   set_identity_matrix(pm);

   rotation_matrix(rm,theta);
   scaling_matrix(sm,sx,sy);
   translation_matrix(tm,tx,ty);
   set_point_matrix(pm,(*p1));
   matrixmultiplicationultiply_matrix(pm,r);
   multiply_matrix(tm,r);
   multiply_matrix(rm,r);
   multiply_matrix(sm,r);
   p1->x = r[0][0];
   p1->y = r[1][0];
}
void set_identity_matrix(float a[maxsize][maxsize])
{
   int i,j;
   for(i = 0; i < maxsize; i++)
   {
	for(j = 0; j < maxsize; j++)
	{
	   a[i][j] = (i==j)? 1:0;
	}
  }
}
void rotation_matrix(float rm[maxsize][maxsize], float theta)
{
   theta =  M_PI * theta /180.0;

   rm[0][0] =  cos(theta);
   rm[0][1] = -sin(theta);
   rm[1][0] =  sin(theta);
   rm[1][1] =  cos(theta);
}
void set_point_matrix(float pm[maxsize][maxsize],struct point p)
{
   pm[0][0] = p.x;
   pm[1][0] = p.y;
   pm[2][0] =    1;
}

void multiply_matrix(float p[maxsize][maxsize],float q[maxsize][maxsize])
{
   float sum,temp[maxsize][maxsize];
   int i,j,k;
   for( i = 0; i < maxsize; i++)
   {
	 for ( j = 0; j < maxsize; j++)
	 {
	   sum = 0;
	   for( k = 0 ; k < maxsize; k++)
	   {
		 sum += (p[i][k]) * (q[k][j]);
	   }
	   temp[i][j] = sum;
	 }
   }
   for( i = 0; i < maxsize; i++)
   {
	for( j = 0; j < maxsize; j++)
	{
	   q[i][j] = temp[i][j];
	}
   }
}


void scaling_matrix(float sm[maxsize][maxsize],float sx, float sy)
{
  sm[0][0] = sx;
  sm[1][1] = sy;
}
void translation_matrix(float tm[maxsize][maxsize], float tx, float ty)
{
  tm[0][2] = tx;
  tm[1][2] = ty;
}