The functions described in this section perform filtering operations in the
Fourier domain. Thus, the input array of such a function should be
compatible with an inverse Fourier transform function, such as the
functions from the numarray.fft module. We therefore have to deal
with arrays that may be the result of a real or a complex Fourier
transform. In the case of a real Fourier transform only half of the of the
symmetric complex transform is stored. Additionally, it needs to be known
what the length of the axis was that was transformed by the real fft. The
functions described here provide a parameter n that in the case of a
real transform must be equal to the length of the real transform axis
before transformation. If this parameter is less than zero, it is assumed
that the input array was the result of a complex Fourier transform. The
parameter axis can be used to indicate along which axis the real
transform was executed.
fourier_shift(
input, shift, n=-1, axis=-1, output=None)
The fourier_shift function multiplies the input array with the
multi-dimensional Fourier transform of a shift operation for the given
shift. The shift parameter is a sequences of shifts for each
dimension, or a single value for all dimensions.
fourier_gaussian(
input, sigma, n=-1, axis=-1, output=None)
The fourier_gaussian function multiplies the input array with
the multi-dimensional Fourier transform of a Gaussian filter with given
standard-deviations sigma. The sigma parameter is a sequences
of values for each dimension, or a single value for all dimensions.
fourier_uniform(
input, size, n=-1, axis=-1, output=None)
The fourier_uniform function multiplies the input array with
the multi-dimensional Fourier transform of a uniform filter with given
sizes size. The size parameter is a sequences of
values for each dimension, or a single value for all dimensions.
fourier_ellipsoid(
input, size, n=-1, axis=-1,
output=None)
The fourier_ellipsoid function multiplies the input array with
the multi-dimensional Fourier transform of a elliptically shaped filter
with given sizes size. The size parameter is a sequences of
values for each dimension, or a single value for all dimensions.
Note:
This function is
only implemented for dimensions 1, 2, and 3.
