/* affine.c */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "mypgm.h"

#define BLACK 0
#define WHITE 255
#define PI 3.141592654

void affine(double x_rot, double y_rot, double x_expan,
    double y_expan, int x_move, int y_move)
     /* affine transformation of input image */
     /* by backward transformation and bilinear interpolation */
     /* input: image1[y][x] -------- output: image2[y][x]   */
{
  double affine[2][2], beta[2];
  double det, i_affine[2][2], i_beta[2];
  double x_new, y_new, x_frac, y_frac;
  double gray_new;
  int gv_new;
  int x, y, m, n;
  
  x_size2 = x_size1;
  y_size2 = y_size1;
  
  /* forward affine transformation */
  affine[0][0] = x_expan * cos(x_rot*PI/180.0);
  affine[0][1] = y_expan * sin(y_rot*PI/180.0);
  affine[1][0] = x_expan * sin(x_rot*PI/180.0);
  affine[1][1] = y_expan * cos(y_rot*PI/180.0);
  beta[0] = x_move;
  beta[1] = y_move;
  
  /* determination of inverse affine transformation */
  det = affine[0][0]*affine[1][1] - affine[0][1]*affine[1][0];
  if (det == 0.0) {
    i_affine[0][0] = 1.0;
    i_affine[0][1] = 0.0;
    i_affine[1][0] = 0.0;
    i_affine[1][1] = 1.0;
    i_beta[0] = -beta[0];
    i_beta[1] = -beta[1];
  } else {
    i_affine[0][0] =  affine[1][1]/det;
    i_affine[0][1] = -affine[0][1]/det;
    i_affine[1][0] = -affine[1][0]/det;
    i_affine[1][1] =  affine[0][0]/det;
    i_beta[0] = -i_affine[0][0]*beta[0]-i_affine[0][1]*beta[1];
    i_beta[1] = -i_affine[1][0]*beta[0]-i_affine[1][1]*beta[1];
  }
  
  /* output image generation by inverse affine transformation
     and bilinear transformation  */
  
  for (y = 0; y < y_size2; y++) {
    for (x = 0; x < x_size2; x++) {
      x_new = i_beta[0] + i_affine[0][0]*(x-x_size2/2.0)
	+ i_affine[0][1]*(y-y_size2/2.0) + x_size2/2.0;
      y_new = i_beta[1] + i_affine[1][0]*(x-x_size2/2.0)
	+ i_affine[1][1]*(y-y_size2/2.0) + y_size2/2.0;
      m = (int)floor(x_new);
      n = (int)floor(y_new);
      x_frac = x_new - m;
      y_frac = y_new - n;
      
      if (m >= 0 && m+1 < x_size2 && n >= 0 && n+1 < y_size2) {
	gray_new = (1.0 - y_frac)*((1.0 - x_frac)*image1[n][m] +
				   x_frac *image1[n][m+1]) +
	  y_frac *((1.0 - x_frac)*image1[n+1][m] +
		   x_frac *image1[n+1][m+1]);
	image2[y][x] = (unsigned char)gray_new;
      } else if (m+1 == x_size2 && n >= 0 && n < y_size2 
		 || n+1 == y_size2 && m >= 0 && m < x_size2) {
	image2[y][x] = image1[n][m];
      } else {
	image2[y][x] = WHITE;
      }
    }
  }
}


main( )
{
  double x_rot, y_rot, x_expan, y_expan;
  int x_move, y_move;
  
  load_image_data( );   /* Input of image1 */
  
  /* affine parameters specification */
  printf("Please enter affine parameters!\n\n");
  printf("X rotation degrees (in real) = ");
  scanf("%lf", &x_rot);
  printf("Y rotation degrees (in real) = ");
  scanf("%lf", &y_rot);
  printf("X expansion rate (in real) = ");
  scanf("%lf", &x_expan);
  printf("Y expansion rate (in real) = ");
  scanf("%lf", &y_expan);
  printf("X translation (in integer) = ");
  scanf("%d", &x_move);
  printf("Y translation (in integer) = ");
  scanf("%d", &y_move);
  printf("\n");
  
  affine(x_rot, y_rot, x_expan, y_expan, x_move, y_move);

  save_image_data( );   /* Output of image2 */

  return 0;
}