Name

filt_tano - hyperbolic tangent homomorphic Fourier filter

Usage

output = filt_tano(image, freq, fall_off, value, pad)

Input

image
input image (can be either real or Fourier)
freq
pass-band frequency
fall_off
fall off of the filter
value
value of the filter at zero frequency
pad
logical flag specifying whether before filtering the image should be padded with zeroes in real space to twice the size (this helps avoiding aliasing artifacts). (Default pad = False).
  • All frequencies are in absolute frequency units `f_a` and their valid range is [0:0.5].

  • Output

    output
    filtered image. Output image is real when input image is real or Fourier when input image is Fourier.

    Method

    Fourier transform of the input image is multiplied by a radially symmetric hyperbolic tangent filter:

    where `f_L` if the the stop-band frequency (freq) and a is the filter fall-off (fall_off).

    Reference

    Basokur, A. T., 1998. Digital filter design using the hyperbolic tangent functions. Journal of the Balkan Geophysical Society 1, 14-18.

    Author / Maintainer

    Pawel A. Penczek

    Keywords

    category 1
    FILTER
    category 2
    FOURIER

    Files

    filter.py

    Maturity

    stable
    works for most people, has been tested; test cases/examples available.

    Bugs

    None. It is perfect.

    filt_tano (last edited 2013-07-01 13:12:58 by localhost)