TRANSFORMÉE DE FOURIER CLASSIQUE

bool CxImage::DFT(int dir,long m,double *x1,double *y1,double *x2,double *y2)
{
   long i,k;
   double arg;
   double cosarg,sinarg;
   
   for (i=0;i<m;i++) {
      x2[i] = 0;
      y2[i] = 0;
      arg = - dir * 2.0 * 3.14159265358f * i / (double)m;
      for (k=0;k<m;k++) {
         cosarg = cos(k * arg);
         sinarg = sin(k * arg);
         x2[i] += (x1[k] * cosarg - y1[k] * sinarg);
         y2[i] += (x1[k] * sinarg + y1[k] * cosarg);
      }
   }
   
   /* Copy the data back */
   if (dir == 1) {
      for (i=0;i<m;i++) {
         x1[i] = x2[i] / m;
         y1[i] = y2[i] / m;
      }
   } else {
      for (i=0;i<m;i++) {
         x1[i] = x2[i];
         y1[i] = y2[i];
      }
   }
   
   return true;
}