Compute the fast Fourier transform of an image.

fft_image 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 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.

fft_image(Image,&FFT);
gen_gabor(&Filter,1.4,0.4,1.0,1.5,512);
convol_gabor(FFT,Filter,&Gabor,&Hilbert);
fft_image_inv(Gabor,&GaborInv);
fft_image_inv(Hilbert,&HilbertInv);
energy_gabor(GaborInv,HilbertInv,&Energy);

fft_image returns 2 (H_MSG_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 handling is raised.

fft_image is reentrant and automatically parallelized (on tuple level).

convol_fft, convol_gabor, convert_image_type, power_byte, power_real, power_ln, phase_deg, phase_rad

fft_generic

fft_image_inv

Image filters