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'.

The filtering is always done on the entire image, i.e., the region of the image is ignored.

my_highpass(Hobject Image, Hobject *Result, int frequency, int size)
{
  Hobject  FFT, Highpass, FFTConvol;
  fft_image(Image,&FFT);
  gen_highpass(&Highpass,frequency,size);
  convol_fft(FFT,Highpass,&FFTConvol); 
  clear_obj(Highpass); clear_obj(FFT);
  fft_image_inv(FFTConvol,Result);
  clear_obj(FFTConvol);
}

convol_fft returns 2 (H_MSG_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 handling is raised.

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

fft_image, fft_generic, gen_highpass, gen_lowpass, gen_bandpass, gen_bandfilter

power_byte, power_real, power_ln, fft_image_inv, fft_generic

convol_gabor

gen_gabor, gen_highpass, gen_lowpass, gen_bandpass, convol_gabor, fft_image_inv

Image filters