fft__ ( Image : ImageFFT : : )

Compute the fast Fourier transform of an image.

fft__ calculates the Fourier transform of the input image (Image), i.e., it transforms the image into the frequency domain. The algorithm used is the fast Fourier transform. This corresponds to the call

     fft_generic(Image:ImageFFT:'to_freq',1,'n','dc_center':)
The result image is of type 'complex'.


Attention

The filtering is always done on the entire image, i.e., the region of the image is ignored. The images must be quadratic and the width and height must be a power of 2.


Parameters

Image (input_object)
image(-array) -> object : byte / real
Input image.

ImageFFT (output_object)
image(-array) -> object : complex
Fourier-transformed image.


Example
fft__(Image,&FFT);
gen_gabor(&Filter,1.4,0.4,1.0,1.5,512);
convol_gabor__(FFT,Filter,&Gabor,&Hilbert);
fft_inv__(Gabor,&GaborInv);
fft_inv__(Hilbert,&HilbertInv);
energy__(GaborInv,HilbertInv,&Energy);

Result

fft__ returns TRUE if the input image is of correct type and its width and height are a power of 2. If the input is empty the behaviour can be set via set_system(::'no_object_result',<Result>:). If necessary, an exception is raised.


Possible Successors

convol_fft__, convol_gabor__, convert_image_type__, power_byte, power_real, power_ln, phase_deg, phase_rad


Alternatives

fft_generic


See also

fft_inv__



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