/** \brief Generic Wavelet-Denoising.
\ingroup grpwavelet
compute DWT of signal, call the thresholding
function 'threshfct' for each resolution level and IDWT the signal
*/
int wavelet_denoise ( double *data, int n, WaveletParameters P ){
gsl_wavelet *w;
gsl_wavelet_workspace *work;
int j, J, k, offset;
double lambda; /* population sd, threshold */
dprintf("Db: generic_denoising\n");
w = gsl_wavelet_alloc( P.wavelet, P.vanishing_moments );
work = gsl_wavelet_workspace_alloc( n );
gsl_wavelet_transform_forward( w, data, 1, n, work );
/* -- thresholding here -- */
J = (int)round(glog((double)n, 2));
for(j=P.first_thresholding_level; j<J; j++){ /* loop through levels */
offset = (int)pow(2, j);
lambda = (*(P.threshselfct))(&(data[offset]), offset);
for(k=offset; k<2*offset; k++){ /* loop through coefficients */
/* soft or hard thresholding */
data[k]=(*(P.threshfct))(data[k], lambda);
}
}
/* -- thresholding end -- */
gsl_wavelet_transform_inverse(w, data, 1, n, work);
gsl_wavelet_free(w);
gsl_wavelet_workspace_free(work);
return 0;
}
int
main (int argc, char **argv)
{
(void)(argc); /* avoid unused parameter warning */
int i, n = 256, nc = 20;
double *data = malloc (n * sizeof (double));
double *abscoeff = malloc (n * sizeof (double));
size_t *p = malloc (n * sizeof (size_t));
FILE * f;
gsl_wavelet *w;
gsl_wavelet_workspace *work;
w = gsl_wavelet_alloc (gsl_wavelet_daubechies, 4);
work = gsl_wavelet_workspace_alloc (n);
f = fopen (argv[1], "r");
for (i = 0; i < n; i++)
{
fscanf (f, "%lg", &data[i]);
}
fclose (f);
gsl_wavelet_transform_forward (w, data, 1, n, work);
for (i = 0; i < n; i++)
{
abscoeff[i] = fabs (data[i]);
}
gsl_sort_index (p, abscoeff, 1, n);
for (i = 0; (i + nc) < n; i++)
data[p[i]] = 0;
gsl_wavelet_transform_inverse (w, data, 1, n, work);
for (i = 0; i < n; i++)
{
printf ("%g\n", data[i]);
}
gsl_wavelet_free (w);
gsl_wavelet_workspace_free (work);
free (data);
free (abscoeff);
free (p);
return 0;
}
