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# Copyright (C) 2003-2005 Peter J. Verveer
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials provided
# with the distribution.
#
# 3. The name of the author may not be used to endorse or promote
# products derived from this software without specific prior
# written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
# GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import numpy as np
from scipy._lib._util import normalize_axis_index
from . import _ni_support
from . import _nd_image
__all__ = ['fourier_gaussian', 'fourier_uniform', 'fourier_ellipsoid',
'fourier_shift']
def _get_output_fourier(output, input):
if output is None:
if input.dtype.type in [np.complex64, np.complex128, np.float32]:
output = np.zeros(input.shape, dtype=input.dtype)
else:
output = np.zeros(input.shape, dtype=np.float64)
elif type(output) is type:
if output not in [np.complex64, np.complex128,
np.float32, np.float64]:
raise RuntimeError("output type not supported")
output = np.zeros(input.shape, dtype=output)
elif output.shape != input.shape:
raise RuntimeError("output shape not correct")
return output
def _get_output_fourier_complex(output, input):
if output is None:
if input.dtype.type in [np.complex64, np.complex128]:
output = np.zeros(input.shape, dtype=input.dtype)
else:
output = np.zeros(input.shape, dtype=np.complex128)
elif type(output) is type:
if output not in [np.complex64, np.complex128]:
raise RuntimeError("output type not supported")
output = np.zeros(input.shape, dtype=output)
elif output.shape != input.shape:
raise RuntimeError("output shape not correct")
return output
def fourier_gaussian(input, sigma, n=-1, axis=-1, output=None):
"""
Multidimensional Gaussian fourier filter.
The array is multiplied with the fourier transform of a Gaussian
kernel.
Parameters
----------
input : array_like
The input array.
sigma : float or sequence
The sigma of the Gaussian kernel. If a float, `sigma` is the same for
all axes. If a sequence, `sigma` has to contain one value for each
axis.
n : int, optional
If `n` is negative (default), then the input is assumed to be the
result of a complex fft.
If `n` is larger than or equal to zero, the input is assumed to be the
result of a real fft, and `n` gives the length of the array before
transformation along the real transform direction.
axis : int, optional
The axis of the real transform.
output : ndarray, optional
If given, the result of filtering the input is placed in this array.
Returns
-------
fourier_gaussian : ndarray
The filtered input.
Examples
--------
>>> from scipy import ndimage, datasets
>>> import numpy.fft
>>> import matplotlib.pyplot as plt
>>> fig, (ax1, ax2) = plt.subplots(1, 2)
>>> plt.gray() # show the filtered result in grayscale
>>> ascent = datasets.ascent()
>>> input_ = numpy.fft.fft2(ascent)
>>> result = ndimage.fourier_gaussian(input_, sigma=4)
>>> result = numpy.fft.ifft2(result)
>>> ax1.imshow(ascent)
>>> ax2.imshow(result.real) # the imaginary part is an artifact
>>> plt.show()
"""
input = np.asarray(input)
output = _get_output_fourier(output, input)
axis = normalize_axis_index(axis, input.ndim)
sigmas = _ni_support._normalize_sequence(sigma, input.ndim)
sigmas = np.asarray(sigmas, dtype=np.float64)
if not sigmas.flags.contiguous:
sigmas = sigmas.copy()
_nd_image.fourier_filter(input, sigmas, n, axis, output, 0)
return output
def fourier_uniform(input, size, n=-1, axis=-1, output=None):
"""
Multidimensional uniform fourier filter.
The array is multiplied with the Fourier transform of a box of given
size.
Parameters
----------
input : array_like
The input array.
size : float or sequence
The size of the box used for filtering.
If a float, `size` is the same for all axes. If a sequence, `size` has
to contain one value for each axis.
n : int, optional
If `n` is negative (default), then the input is assumed to be the
result of a complex fft.
If `n` is larger than or equal to zero, the input is assumed to be the
result of a real fft, and `n` gives the length of the array before
transformation along the real transform direction.
axis : int, optional
The axis of the real transform.
output : ndarray, optional
If given, the result of filtering the input is placed in this array.
Returns
-------
fourier_uniform : ndarray
The filtered input.
Examples
--------
>>> from scipy import ndimage, datasets
>>> import numpy.fft
>>> import matplotlib.pyplot as plt
>>> fig, (ax1, ax2) = plt.subplots(1, 2)
>>> plt.gray() # show the filtered result in grayscale
>>> ascent = datasets.ascent()
>>> input_ = numpy.fft.fft2(ascent)
>>> result = ndimage.fourier_uniform(input_, size=20)
>>> result = numpy.fft.ifft2(result)
>>> ax1.imshow(ascent)
>>> ax2.imshow(result.real) # the imaginary part is an artifact
>>> plt.show()
"""
input = np.asarray(input)
output = _get_output_fourier(output, input)
axis = normalize_axis_index(axis, input.ndim)
sizes = _ni_support._normalize_sequence(size, input.ndim)
sizes = np.asarray(sizes, dtype=np.float64)
if not sizes.flags.contiguous:
sizes = sizes.copy()
_nd_image.fourier_filter(input, sizes, n, axis, output, 1)
return output
def fourier_ellipsoid(input, size, n=-1, axis=-1, output=None):
"""
Multidimensional ellipsoid Fourier filter.
The array is multiplied with the fourier transform of an ellipsoid of
given sizes.
Parameters
----------
input : array_like
The input array.
size : float or sequence
The size of the box used for filtering.
If a float, `size` is the same for all axes. If a sequence, `size` has
to contain one value for each axis.
n : int, optional
If `n` is negative (default), then the input is assumed to be the
result of a complex fft.
If `n` is larger than or equal to zero, the input is assumed to be the
result of a real fft, and `n` gives the length of the array before
transformation along the real transform direction.
axis : int, optional
The axis of the real transform.
output : ndarray, optional
If given, the result of filtering the input is placed in this array.
Returns
-------
fourier_ellipsoid : ndarray
The filtered input.
Notes
-----
This function is implemented for arrays of rank 1, 2, or 3.
Examples
--------
>>> from scipy import ndimage, datasets
>>> import numpy.fft
>>> import matplotlib.pyplot as plt
>>> fig, (ax1, ax2) = plt.subplots(1, 2)
>>> plt.gray() # show the filtered result in grayscale
>>> ascent = datasets.ascent()
>>> input_ = numpy.fft.fft2(ascent)
>>> result = ndimage.fourier_ellipsoid(input_, size=20)
>>> result = numpy.fft.ifft2(result)
>>> ax1.imshow(ascent)
>>> ax2.imshow(result.real) # the imaginary part is an artifact
>>> plt.show()
"""
input = np.asarray(input)
if input.ndim > 3:
raise NotImplementedError("Only 1d, 2d and 3d inputs are supported")
output = _get_output_fourier(output, input)
if output.size == 0:
# The C code has a bug that can result in a segfault with arrays
# that have size 0 (gh-17270), so check here.
return output
axis = normalize_axis_index(axis, input.ndim)
sizes = _ni_support._normalize_sequence(size, input.ndim)
sizes = np.asarray(sizes, dtype=np.float64)
if not sizes.flags.contiguous:
sizes = sizes.copy()
_nd_image.fourier_filter(input, sizes, n, axis, output, 2)
return output
def fourier_shift(input, shift, n=-1, axis=-1, output=None):
"""
Multidimensional Fourier shift filter.
The array is multiplied with the Fourier transform of a shift operation.
Parameters
----------
input : array_like
The input array.
shift : float or sequence
The size of the box used for filtering.
If a float, `shift` is the same for all axes. If a sequence, `shift`
has to contain one value for each axis.
n : int, optional
If `n` is negative (default), then the input is assumed to be the
result of a complex fft.
If `n` is larger than or equal to zero, the input is assumed to be the
result of a real fft, and `n` gives the length of the array before
transformation along the real transform direction.
axis : int, optional
The axis of the real transform.
output : ndarray, optional
If given, the result of shifting the input is placed in this array.
Returns
-------
fourier_shift : ndarray
The shifted input.
Examples
--------
>>> from scipy import ndimage, datasets
>>> import matplotlib.pyplot as plt
>>> import numpy.fft
>>> fig, (ax1, ax2) = plt.subplots(1, 2)
>>> plt.gray() # show the filtered result in grayscale
>>> ascent = datasets.ascent()
>>> input_ = numpy.fft.fft2(ascent)
>>> result = ndimage.fourier_shift(input_, shift=200)
>>> result = numpy.fft.ifft2(result)
>>> ax1.imshow(ascent)
>>> ax2.imshow(result.real) # the imaginary part is an artifact
>>> plt.show()
"""
input = np.asarray(input)
output = _get_output_fourier_complex(output, input)
axis = normalize_axis_index(axis, input.ndim)
shifts = _ni_support._normalize_sequence(shift, input.ndim)
shifts = np.asarray(shifts, dtype=np.float64)
if not shifts.flags.contiguous:
shifts = shifts.copy()
_nd_image.fourier_shift(input, shifts, n, axis, output)
return output
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