/*********************************************************/
/*   program 21: translate                               */
/*********************************************************/

#define  XSIZE  640
#define  YSIZE  480

#define  RED    0
#define  GREEN  1
#define  BLUE   2

#define  XOFF   65.4
#define  YOFF   24.8
#define  INTERP 1

main()
  {
  unsigned char *ir,*ig,*ib;
  unsigned char *or,*og,*ob;
  unsigned char *i,*o;
  long  int  ix,iy,c;
  long  int  ix0,iy0;
  long  int  ix1,iy1;
  long  int  ox,oy;
  long  int  cx,cy;
  double     X,Y;
  double     DX,DY;
  double     A,B,C,D,AB,CD;
  double     v;

  /* allocate input and output memory buffers */
  ir = (unsigned char *) malloc (XSIZE*YSIZE);
  ig = (unsigned char *) malloc (XSIZE*YSIZE);
  ib = (unsigned char *) malloc (XSIZE*YSIZE);
  or = (unsigned char *) malloc (XSIZE*YSIZE);
  og = (unsigned char *) malloc (XSIZE*YSIZE);
  ob = (unsigned char *) malloc (XSIZE*YSIZE);

  /* read the input image */
  read_image("input",ir,ig,ib);

  /* process all lines of image */
  for (oy = 0; oy < YSIZE; oy++)
    {
    for (ox = 0; ox < XSIZE; ox++)
      {
      /* process the red, green, and blue planes one at a time */
      for (c = RED; c <= BLUE; c++)
        {
        /* initialize pointers for current color plane */
        if (c == RED  ) i = ir;
        if (c == GREEN) i = ig;
        if (c == BLUE ) i = ib;
        if (c == RED  ) o = or;
        if (c == GREEN) o = og;
        if (c == BLUE ) o = ob;

        if (INTERP == 0)
          {
          /* nearest neighbor */
          ix = ox - (long int)(XOFF + 0.5);
          iy = oy - (long int)(YOFF + 0.5);
          if ((ix >= 0) && (ix < XSIZE) && (iy >= 0) && (iy < YSIZE))
            o[(oy*XSIZE)+ox] = i[(iy*XSIZE)+ix];
          else
            o[(oy*XSIZE)+ox] = 0x0;
          }

        else
          {
          /* bilinear interpolation */
          X = (double)ox - XOFF;
          if (X >= 0.0)
            ix0 = (long)X;
          else
            ix0 = (long)(X-1.0);

          Y = (double)oy - YOFF;
          if (Y >= 0.0)
            iy0 = (long)Y;
          else
            iy0 = (long)(Y-1.0);

          ix1 = ix0 + 1;
          iy1 = iy0 + 1;
          DX = X - (double)ix0;
          DY = Y - (double)iy0;
          A = 0.0;
          B = 0.0;
          C = 0.0;
          D = 0.0;

          if ((ix0 >= 0) && (ix0 < XSIZE) && (iy0 >= 0) && (iy0 < YSIZE))
            A = (float)i[(iy0*XSIZE)+ix0];
          if ((ix1 >= 0) && (ix1 < XSIZE) && (iy0 >= 0) && (iy0 < YSIZE))
            B = (float)i[(iy0*XSIZE)+ix1];
          if ((ix0 >= 0) && (ix0 < XSIZE) && (iy1 >= 0) && (iy1 < YSIZE))
            C = (float)i[(iy1*XSIZE)+ix0];
          if ((ix1 >= 0) && (ix1 < XSIZE) && (iy1 >= 0) && (iy1 < YSIZE))
            D = (float)i[(iy1*XSIZE)+ix1];

          AB = (A * (1.0-DX)) + (B * DX);
          CD = (C * (1.0-DX)) + (D * DX);
          v  = (AB * (1.0-DY)) + (CD * DY);

          o[(oy*XSIZE)+ox] = (unsigned char)v;
          }
        }
      }
    }

  /* write the output image */
  write_image("output",or,og,ob);

  /* free memory buffers */
  free(ir);
  free(ig);
  free(ib);
  free(or);
  free(og);
  free(ob);
}