Rotation

#include<graphics.h>
#include<conio.h>
#include<stdio.h>
#include<math.h>
typedef struct origin
{
int x,y;
}PT;
#define r 3
#define c 3
double mat[r][c];
PT pt[4];
void funtransform(int p);
void funrotate(double a);
void funsetidentity(double mm[r][c]);
void main()
{
 int gd=DETECT,gm,i,j,p,a,ch;
 clrscr();
 printf("\n\n Rotate Object Prog");
 printf("\n \t.....................");
 printf("\n\n 1>Line:");
 printf("\n\n 2>triangle");
 printf("\n\n 3>Rectangle:");
 printf("\n.............");
 printf("\n\n Enter Your choice:-");
 scanf("%d",&ch);
 switch(ch)
 {
  case 1:
  p=2;
  break;
  case 2:
  p=1;
  break;
  case 3:
  p=3;
  break;
  case 4:
  p=4;
  break;
  default:
  p=0;
 }
 if(p==0)
 exit();
 for(i=0;i<p;i++)
 {
  printf("\n Enter X- %d and Y-%d",i,i);
  scanf("%d %d",&pt[i].x,&pt[i].y);
 }
 printf("\n Enter Angle:-");
 scanf("%d",&a);
 clrscr();
 initgraph(&gd,&gm,"c:\\tc\\bgi");
 outtextxy(280,10,"Original Object");
  switch(ch)
 {
  case 1:
  line (pt[0].x,pt[0].y,pt[1].x,pt[1].y);
  break;
  case 2:
  circle(pt[0].x,pt[0].y,50);
  break;
   /*case 3:
   triangle(pt[0].x,pt[0].y,pt[1].x,pt[1].y,pt[2].x,pt[2].y);
   break;*/
   case 4:
   rectangle(pt[0].x,pt[0].y,pt[2].x,pt[2].y);
   break;
 }

 //fillpoly(p,pt);
 getch();
 cleardevice();
 funsetidentity(mat);
 funrotate(a);
 funtransform(p);
 outtextxy(100,10,"rotate Object");
  switch(ch)
 {
  case 1:
  line (pt[0].x,pt[0].y,pt[1].x,pt[1].y);
  break;
  case 2:
  circle(pt[0].x,pt[0].y,50);
  break;
   /*case 3:
   triangle(pt[0].x,pt[0].y,pt[1].x,pt[1].y,pt[2].x,pt[2].y);
   break;*/
   case 4:
   rectangle(pt[0].x,pt[0].y,pt[2].x,pt[2].y);
   break;
 }

 //fillpoly(p,pt);
 getch();
 closegraph();
}


void funsetidentity(double mm[r][c])
{
 int i,j;
 for(i=1;i<=r;i++)
 {
  for(j=1;j<=c;j++)
  {
   if(i==j)
   mm[i][j]=1.0;
   else
   mm[i][j]=0.0;
  }
 }
}
void funrotate (double a)
{
 a=a*M_PI/180.00;
 mat[1][1]=cos(a);
 mat[1][2]=sin(a);
 mat[2][1]=-sin(a);
 mat[2][2]=cos(a);
}
void funtransform(int p)
{
 int i,j;
 double temp;
 for(i=0;i<p;i++)
 {
  temp=(int)mat[1][1]*pt[i].x+mat[1][2]*pt[i].y+mat[1][3];
  pt[i].y=(int)mat[1][2]*pt[i].x+mat[2][2]*pt[i].y+mat[2][3];
  pt[i].x=(int)temp;
 }
}