convol_fft__ ( ImageFFT, ImageFilter : ImageConvol : : )

Convolve an image with a byte-mask in the frequency domain.

convol_fft__ convolves two (Fourier-transformed) images in the frequency domain, i.e., the pixels of the complex image ImageFFT are multiplied by the corresponding pixels of the filter ImageFilter. This image is a byte-image in which 0 corresponds to complete suppression of a frequency, and 255 corresponds to no suppression. 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.


Parameters

ImageFFT (input_object)
image(-array) -> object : complex
Complex input image.

ImageFilter (input_object)
image -> object : byte
Filter in frequency domain.

ImageConvol (output_object)
image(-array) -> object : complex
Result of applying the filter.


Example
my_highpass(ObjType Image, ObjType *Result, int frequency, int size)
{
  ObjType  FFT, Highpass, FFTConvol;
  fft__(Image,&FFT);
  gen_highpass(&Highpass,frequency,size);
  convol_fft__(FFT,Highpass,&FFTConvol); 
  clear(Highpass); clear(FFT);
  fft_inv__(FFTConvol,Result);
  clear(FFTConvol);
}

Result

convol_fft__ returns TRUE if all parameters are correct. If the input is empty the behaviour can be set via set_system(::'no_object_result',<Result>:). If necessary, an exception is raised.


Possible Predecessors

fft__, fft_generic, gen_highpass, gen_lowpass, gen_bandpass, gen_bandfilter


Possible Successors

power_byte, power_real, power_ln, fft_inv__, fft_generic


Alternatives

convol_gabor__


See also

gen_gabor, gen_highpass, gen_lowpass, gen_bandpass, convol_gabor__, fft_inv__



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