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Name

filt_tanh - hyperbolic tangent high-pass Fourier filter

Usage

output = filt_tanh(image, freq, fall_off, pad)

Input

image
input image (can be either real or Fourier)
freq
pass-band frequency
fall_off
fall off of the filter
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).

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_H` if the the pass-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.