Name

filt_gaussinv - inverse Gaussian (high-pass) Fourier filter (division by a Gaussian function in Fourier space)

Usage

output = filt_gaussinv(image, sigma, pad)

Input

image

input image (can be either real or Fourier)

sigma

standard deviation of the Gaussian function in absolute frequency units `f_a`.

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).

• Note: for sigma = 0.5 (the Nyquist frequency) the value of the filter at the maximum frequency is `G(f_N)=sqrt(e)=1.65`.

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 inverse Gaussian filter:

• `G(f) = exp(f^2/(2 sigma^2))`

Reference

Gonzalez, R. F., Woods, R. E., 2002. Digital Image Processing. Prentice Hall, Upper Saddle River, NJ.

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.