
 lowpass, highpass, bandpass, bandstop, butterworth, exponential, lowpassIdeal, fftMakeLp, fftMakeHp, fftMakeBp, ... 
  lowpass, highpass, bandpass, bandstop, butterworth, exponential, lowpassIdeal, fftMakeLp, fftMakeHp, fftMakeBp, fftMakeBs 
  The filter used is an ideal lowpass filter truncated with a circularly symmetric window function in the image domain. 
  This filter is the boxshaped ideal frequency response which corresponds to a nonrealizable spatialdomain filter. 
 www.ifi.uio.no /forskning/grupper/dsb/Programvare/Xite/ReferenceManual/lowpass_1.html (455 words) 
