simpleFFT — Simple FFT algorithm
void | gwy_fft_simple () |
void | gwy_fft_window () |
void | gwy_fft_window_data_field () |
#include <libprocess/gwyprocess.h>
The simple one-dimensional FFT algorithm gwy_fft_simple()
used to be
employed as a fallback by other functions when a better implementation
(FFTW3) was not available. Since version 2.49 it just calls the
corresponding FFTW routine.
Generally, you should either use high-level Gwyddion functions such as
gwy_data_field_2dfft_raw()
or, if they are insufficient, FFTW routines
directly.
Up to version 2.7 simpleFFT required certain tranform sizes, mostly powers of 2. Since 2.8 it can handle arbitrary tranform sizes, although sizes with large prime factors can be quite slow (still O(n*log(n)) though).
void gwy_fft_simple (GwyTransformDirection dir
,gint n
,gint istride
,const gdouble *in_re
,const gdouble *in_im
,gint ostride
,gdouble *out_re
,gdouble *out_im
);
Performs a DFT algorithm.
This is a low-level function that used to be employed by other FFT functions when no better backend was available. Since version 2.49 it just calls the corresponding FFTW routine.
Strides are distances between samples in input and output arrays. Use 1
for normal `dense' arrays. To use gwy_fft_simple()
with interleaved arrays,
that is with alternating real and imaginary data, call it with
istride
=2, in_re
=complex_array
, in_im
=complex_array
+1 (and similarly
for output arrays).
The output is symmetrically normalized by square root of n
for both
transform directions. By performing forward and then backward transform,
you will obtain the original array (up to rounding errors).
dir |
Transformation direction. |
|
n |
Number of data points. Note only certain transform sizes are
implemented. If |
|
istride |
Input data stride. |
|
in_re |
Real part of input data. |
|
in_im |
Imaginary part of input data. |
|
ostride |
Output data stride. |
|
out_re |
Real part of output data. |
|
out_im |
Imaginary part of output data. |
void gwy_fft_window (gint n
,gdouble *data
,GwyWindowingType windowing
);
Multiplies data by given window.
n |
Number of data values. |
|
data |
Data values. |
|
windowing |
Method used for windowing. |
void gwy_fft_window_data_field (GwyDataField *dfield
,GwyOrientation orientation
,GwyWindowingType windowing
);
Performs windowing of a data field in given direction.
dfield |
A data field. |
|
orientation |
Windowing orientation (the same as corresponding FFT orientation). |
|
windowing |
The windowing type to use. |
-- high-level integral transform functions