filt_tanh112013-07-01 13:12:58localhostconverted to 1.6 markup102010-07-02 18:34:47139.52.19.6492007-08-13 16:29:00penczek82007-06-21 20:24:17bmb24.med.uth.tmc.edu72007-06-20 21:31:30bmb24.med.uth.tmc.edu62007-06-20 21:03:31bmb24.med.uth.tmc.edu52006-07-23 19:49:51penczek42006-07-23 19:49:36penczek32006-07-23 19:46:58penczek22006-07-23 19:27:13penczek12006-07-23 19:26:26penczekNamefilt_tanh - hyperbolic tangent high-pass Fourier filter Usageoutput = filt_tanh(image, freq, fall_off, pad) Inputimageinput image (can be either real or Fourier) freqpass-band frequency fall_offfall off of the filter padlogical 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]. Outputoutputfiltered image. Output image is real when input image is real or Fourier when input image is Fourier MethodFourier transform of the input image is multiplied by a radially symmetric hyperbolic tangent filter: ``H(f) = 1.0-0.5{tanh[(pi(f+f_H))/(2af_H))]-tanh[(pi(f-f_H))/(2af_H))]}``

where ``f_H``

if the the pass-band frequency (freq) and a is the filter fall-off (fall_off). ReferenceBasokur, A. T., 1998. Digital filter design using the hyperbolic tangent functions. Journal of the Balkan Geophysical Society 1, 14-18. Author / MaintainerPawel A. Penczek Keywordscategory 1FILTER category 2FOURIER Maturitystableworks for most people, has been tested; test cases/examples available.