Functions
int  vips_fwfft () 
int  vips_invfft () 
int  vips_freqmult () 
int  vips_spectrum () 
int  vips_phasecor () 
Description
To and from Fourier space, filter in Fourier space, convert Fourierspace images to a displayable form.
Functions
vips_fwfft ()
int vips_fwfft (VipsImage *in
,VipsImage **out
,...
);
Transform an image to Fourier space.
VIPS uses the fftw Fourier Transform library. If this library was not available when VIPS was configured, these functions will fail.
See also: vips_invfft()
.
vips_invfft ()
int vips_invfft (VipsImage *in
,VipsImage **out
,...
);
Optional arguments:

real
: only output the real part
Transform an image from Fourier space to real space. The result is complex.
If you are OK with a real result, set real
, it's quicker.
VIPS uses the fftw Fourier Transform library. If this library was not available when VIPS was configured, these functions will fail.
See also: vips_fwfft()
.
vips_freqmult ()
int vips_freqmult (VipsImage *in
,VipsImage *mask
,VipsImage **out
,...
);
Multiply in
by mask
in Fourier space.
in
is transformed to Fourier space, multipled with mask
, then
transformed back to real space. If in
is already a complex image, just
multiply then inverse transform.
See also: vips_invfft()
, vips_mask_ideal()
.
Parameters
in 
input image 

mask 
mask image 

out 
output image 

... 

vips_spectrum ()
int vips_spectrum (VipsImage *in
,VipsImage **out
,...
);
Make a displayable (ie. 8bit unsigned int) power spectrum.
If in
is noncomplex, it is transformed to Fourier space. Then the
absolute value is passed through vips_scale()
in log mode, and vips_wrap()
.
See also: vips_fwfft()
, vips_scale()
, vips_wrap()
.
vips_phasecor ()
int vips_phasecor (VipsImage *in1
,VipsImage *in2
,VipsImage **out
,...
);
Convert the two input images to Fourier space, calculate phasecorrelation, back to real space.
See also: vips_fwfft()
, vips_cross_phase()
,
Parameters
in1 
first input image 

in2 
second input image 

out 
output image 

... 
