/
filters.py
1187 lines (1053 loc) · 39.5 KB
/
filters.py
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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.
from __future__ import division, print_function, absolute_import
import math
import numpy
from . import _ni_support
from . import _nd_image
from scipy.misc import doccer
from scipy.lib._version import NumpyVersion
__all__ = ['correlate1d', 'convolve1d', 'gaussian_filter1d', 'gaussian_filter',
'prewitt', 'sobel', 'generic_laplace', 'laplace',
'gaussian_laplace', 'generic_gradient_magnitude',
'gaussian_gradient_magnitude', 'correlate', 'convolve',
'uniform_filter1d', 'uniform_filter', 'minimum_filter1d',
'maximum_filter1d', 'minimum_filter', 'maximum_filter',
'rank_filter', 'median_filter', 'percentile_filter',
'generic_filter1d', 'generic_filter']
_input_doc = \
"""input : array_like
Input array to filter."""
_axis_doc = \
"""axis : int, optional
The axis of `input` along which to calculate. Default is -1."""
_output_doc = \
"""output : array, optional
The `output` parameter passes an array in which to store the
filter output."""
_size_foot_doc = \
"""size : scalar or tuple, optional
See footprint, below
footprint : array, optional
Either `size` or `footprint` must be defined. `size` gives
the shape that is taken from the input array, at every element
position, to define the input to the filter function.
`footprint` is a boolean array that specifies (implicitly) a
shape, but also which of the elements within this shape will get
passed to the filter function. Thus ``size=(n,m)`` is equivalent
to ``footprint=np.ones((n,m))``. We adjust `size` to the number
of dimensions of the input array, so that, if the input array is
shape (10,10,10), and `size` is 2, then the actual size used is
(2,2,2).
"""
_mode_doc = \
"""mode : {'reflect', 'constant', 'nearest', 'mirror', 'wrap'}, optional
The `mode` parameter determines how the array borders are
handled, where `cval` is the value when mode is equal to
'constant'. Default is 'reflect'"""
_cval_doc = \
"""cval : scalar, optional
Value to fill past edges of input if `mode` is 'constant'. Default
is 0.0"""
_origin_doc = \
"""origin : scalar, optional
The `origin` parameter controls the placement of the filter.
Default 0.0."""
_extra_arguments_doc = \
"""extra_arguments : sequence, optional
Sequence of extra positional arguments to pass to passed function"""
_extra_keywords_doc = \
"""extra_keywords : dict, optional
dict of extra keyword arguments to pass to passed function"""
docdict = {
'input': _input_doc,
'axis': _axis_doc,
'output': _output_doc,
'size_foot': _size_foot_doc,
'mode': _mode_doc,
'cval': _cval_doc,
'origin': _origin_doc,
'extra_arguments': _extra_arguments_doc,
'extra_keywords': _extra_keywords_doc,
}
docfiller = doccer.filldoc(docdict)
@docfiller
def correlate1d(input, weights, axis=-1, output=None, mode="reflect",
cval=0.0, origin=0):
"""Calculate a one-dimensional correlation along the given axis.
The lines of the array along the given axis are correlated with the
given weights.
Parameters
----------
%(input)s
weights : array
One-dimensional sequence of numbers.
%(axis)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
"""
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
output, return_value = _ni_support._get_output(output, input)
weights = numpy.asarray(weights, dtype=numpy.float64)
if weights.ndim != 1 or weights.shape[0] < 1:
raise RuntimeError('no filter weights given')
if not weights.flags.contiguous:
weights = weights.copy()
axis = _ni_support._check_axis(axis, input.ndim)
if (len(weights) // 2 + origin < 0) or (len(weights) // 2 +
origin > len(weights)):
raise ValueError('invalid origin')
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.correlate1d(input, weights, axis, output, mode, cval,
origin)
return return_value
@docfiller
def convolve1d(input, weights, axis=-1, output=None, mode="reflect",
cval=0.0, origin=0):
"""Calculate a one-dimensional convolution along the given axis.
The lines of the array along the given axis are convolved with the
given weights.
Parameters
----------
%(input)s
weights : ndarray
One-dimensional sequence of numbers.
%(axis)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
Returns
-------
convolve1d : ndarray
Convolved array with same shape as input
"""
weights = weights[::-1]
origin = -origin
if not len(weights) & 1:
origin -= 1
return correlate1d(input, weights, axis, output, mode, cval, origin)
@docfiller
def gaussian_filter1d(input, sigma, axis=-1, order=0, output=None,
mode="reflect", cval=0.0, truncate=4.0):
"""One-dimensional Gaussian filter.
Parameters
----------
%(input)s
sigma : scalar
standard deviation for Gaussian kernel
%(axis)s
order : {0, 1, 2, 3}, optional
An order of 0 corresponds to convolution with a Gaussian
kernel. An order of 1, 2, or 3 corresponds to convolution with
the first, second or third derivatives of a Gaussian. Higher
order derivatives are not implemented
%(output)s
%(mode)s
%(cval)s
truncate : float
Truncate the filter at this many standard deviations.
Default is 4.0.
Returns
-------
gaussian_filter1d : ndarray
"""
if order not in range(4):
raise ValueError('Order outside 0..3 not implemented')
sd = float(sigma)
# make the radius of the filter equal to truncate standard deviations
lw = int(truncate * sd + 0.5)
weights = [0.0] * (2 * lw + 1)
weights[lw] = 1.0
sum = 1.0
sd = sd * sd
# calculate the kernel:
for ii in range(1, lw + 1):
tmp = math.exp(-0.5 * float(ii * ii) / sd)
weights[lw + ii] = tmp
weights[lw - ii] = tmp
sum += 2.0 * tmp
for ii in range(2 * lw + 1):
weights[ii] /= sum
# implement first, second and third order derivatives:
if order == 1: # first derivative
weights[lw] = 0.0
for ii in range(1, lw + 1):
x = float(ii)
tmp = -x / sd * weights[lw + ii]
weights[lw + ii] = -tmp
weights[lw - ii] = tmp
elif order == 2: # second derivative
weights[lw] *= -1.0 / sd
for ii in range(1, lw + 1):
x = float(ii)
tmp = (x * x / sd - 1.0) * weights[lw + ii] / sd
weights[lw + ii] = tmp
weights[lw - ii] = tmp
elif order == 3: # third derivative
weights[lw] = 0.0
sd2 = sd * sd
for ii in range(1, lw + 1):
x = float(ii)
tmp = (3.0 - x * x / sd) * x * weights[lw + ii] / sd2
weights[lw + ii] = -tmp
weights[lw - ii] = tmp
return correlate1d(input, weights, axis, output, mode, cval, 0)
@docfiller
def gaussian_filter(input, sigma, order=0, output=None,
mode="reflect", cval=0.0, truncate=4.0):
"""Multidimensional Gaussian filter.
Parameters
----------
%(input)s
sigma : scalar or sequence of scalars
Standard deviation for Gaussian kernel. The standard
deviations of the Gaussian filter are given for each axis as a
sequence, or as a single number, in which case it is equal for
all axes.
order : {0, 1, 2, 3} or sequence from same set, optional
The order of the filter along each axis is given as a sequence
of integers, or as a single number. An order of 0 corresponds
to convolution with a Gaussian kernel. An order of 1, 2, or 3
corresponds to convolution with the first, second or third
derivatives of a Gaussian. Higher order derivatives are not
implemented
%(output)s
%(mode)s
%(cval)s
truncate : float
Truncate the filter at this many standard deviations.
Default is 4.0.
Returns
-------
gaussian_filter : ndarray
Returned array of same shape as `input`.
Notes
-----
The multidimensional filter is implemented as a sequence of
one-dimensional convolution filters. The intermediate arrays are
stored in the same data type as the output. Therefore, for output
types with a limited precision, the results may be imprecise
because intermediate results may be stored with insufficient
precision.
"""
input = numpy.asarray(input)
output, return_value = _ni_support._get_output(output, input)
orders = _ni_support._normalize_sequence(order, input.ndim)
if not set(orders).issubset(set(range(4))):
raise ValueError('Order outside 0..4 not implemented')
sigmas = _ni_support._normalize_sequence(sigma, input.ndim)
axes = list(range(input.ndim))
axes = [(axes[ii], sigmas[ii], orders[ii])
for ii in range(len(axes)) if sigmas[ii] > 1e-15]
if len(axes) > 0:
for axis, sigma, order in axes:
gaussian_filter1d(input, sigma, axis, order, output,
mode, cval, truncate)
input = output
else:
output[...] = input[...]
return return_value
@docfiller
def prewitt(input, axis=-1, output=None, mode="reflect", cval=0.0):
"""Calculate a Prewitt filter.
Parameters
----------
%(input)s
%(axis)s
%(output)s
%(mode)s
%(cval)s
"""
input = numpy.asarray(input)
axis = _ni_support._check_axis(axis, input.ndim)
output, return_value = _ni_support._get_output(output, input)
correlate1d(input, [-1, 0, 1], axis, output, mode, cval, 0)
axes = [ii for ii in range(input.ndim) if ii != axis]
for ii in axes:
correlate1d(output, [1, 1, 1], ii, output, mode, cval, 0,)
return return_value
@docfiller
def sobel(input, axis=-1, output=None, mode="reflect", cval=0.0):
"""Calculate a Sobel filter.
Parameters
----------
%(input)s
%(axis)s
%(output)s
%(mode)s
%(cval)s
"""
input = numpy.asarray(input)
axis = _ni_support._check_axis(axis, input.ndim)
output, return_value = _ni_support._get_output(output, input)
correlate1d(input, [-1, 0, 1], axis, output, mode, cval, 0)
axes = [ii for ii in range(input.ndim) if ii != axis]
for ii in axes:
correlate1d(output, [1, 2, 1], ii, output, mode, cval, 0)
return return_value
@docfiller
def generic_laplace(input, derivative2, output=None, mode="reflect",
cval=0.0,
extra_arguments=(),
extra_keywords = None):
"""N-dimensional Laplace filter using a provided second derivative function
Parameters
----------
%(input)s
derivative2 : callable
Callable with the following signature::
derivative2(input, axis, output, mode, cval,
*extra_arguments, **extra_keywords)
See `extra_arguments`, `extra_keywords` below.
%(output)s
%(mode)s
%(cval)s
%(extra_keywords)s
%(extra_arguments)s
"""
if extra_keywords is None:
extra_keywords = {}
input = numpy.asarray(input)
output, return_value = _ni_support._get_output(output, input)
axes = list(range(input.ndim))
if len(axes) > 0:
derivative2(input, axes[0], output, mode, cval,
*extra_arguments, **extra_keywords)
for ii in range(1, len(axes)):
tmp = derivative2(input, axes[ii], output.dtype, mode, cval,
*extra_arguments, **extra_keywords)
output += tmp
else:
output[...] = input[...]
return return_value
@docfiller
def laplace(input, output=None, mode="reflect", cval=0.0):
"""N-dimensional Laplace filter based on approximate second derivatives.
Parameters
----------
%(input)s
%(output)s
%(mode)s
%(cval)s
"""
def derivative2(input, axis, output, mode, cval):
return correlate1d(input, [1, -2, 1], axis, output, mode, cval, 0)
return generic_laplace(input, derivative2, output, mode, cval)
@docfiller
def gaussian_laplace(input, sigma, output=None, mode="reflect",
cval=0.0, **kwargs):
"""Multidimensional Laplace filter using gaussian second derivatives.
Parameters
----------
%(input)s
sigma : scalar or sequence of scalars
The standard deviations of the Gaussian filter are given for
each axis as a sequence, or as a single number, in which case
it is equal for all axes.
%(output)s
%(mode)s
%(cval)s
Extra keyword arguments will be passed to gaussian_filter().
"""
input = numpy.asarray(input)
def derivative2(input, axis, output, mode, cval, sigma, **kwargs):
order = [0] * input.ndim
order[axis] = 2
return gaussian_filter(input, sigma, order, output, mode, cval,
**kwargs)
return generic_laplace(input, derivative2, output, mode, cval,
extra_arguments=(sigma,),
extra_keywords=kwargs)
@docfiller
def generic_gradient_magnitude(input, derivative, output=None,
mode="reflect", cval=0.0,
extra_arguments=(), extra_keywords = None):
"""Gradient magnitude using a provided gradient function.
Parameters
----------
%(input)s
derivative : callable
Callable with the following signature::
derivative(input, axis, output, mode, cval,
*extra_arguments, **extra_keywords)
See `extra_arguments`, `extra_keywords` below.
`derivative` can assume that `input` and `output` are ndarrays.
Note that the output from `derivative` is modified inplace;
be careful to copy important inputs before returning them.
%(output)s
%(mode)s
%(cval)s
%(extra_keywords)s
%(extra_arguments)s
"""
if extra_keywords is None:
extra_keywords = {}
input = numpy.asarray(input)
output, return_value = _ni_support._get_output(output, input)
axes = list(range(input.ndim))
if len(axes) > 0:
derivative(input, axes[0], output, mode, cval,
*extra_arguments, **extra_keywords)
numpy.multiply(output, output, output)
for ii in range(1, len(axes)):
tmp = derivative(input, axes[ii], output.dtype, mode, cval,
*extra_arguments, **extra_keywords)
numpy.multiply(tmp, tmp, tmp)
output += tmp
# This allows the sqrt to work with a different default casting
if NumpyVersion(numpy.__version__) > '1.6.1':
numpy.sqrt(output, output, casting='unsafe')
else:
numpy.sqrt(output, output)
else:
output[...] = input[...]
return return_value
@docfiller
def gaussian_gradient_magnitude(input, sigma, output=None,
mode="reflect", cval=0.0, **kwargs):
"""Multidimensional gradient magnitude using Gaussian derivatives.
Parameters
----------
%(input)s
sigma : scalar or sequence of scalars
The standard deviations of the Gaussian filter are given for
each axis as a sequence, or as a single number, in which case
it is equal for all axes..
%(output)s
%(mode)s
%(cval)s
Extra keyword arguments will be passed to gaussian_filter().
"""
input = numpy.asarray(input)
def derivative(input, axis, output, mode, cval, sigma, **kwargs):
order = [0] * input.ndim
order[axis] = 1
return gaussian_filter(input, sigma, order, output, mode,
cval, **kwargs)
return generic_gradient_magnitude(input, derivative, output, mode,
cval, extra_arguments=(sigma,),
extra_keywords=kwargs)
def _correlate_or_convolve(input, weights, output, mode, cval, origin,
convolution):
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
origins = _ni_support._normalize_sequence(origin, input.ndim)
weights = numpy.asarray(weights, dtype=numpy.float64)
wshape = [ii for ii in weights.shape if ii > 0]
if len(wshape) != input.ndim:
raise RuntimeError('filter weights array has incorrect shape.')
if convolution:
weights = weights[tuple([slice(None, None, -1)] * weights.ndim)]
for ii in range(len(origins)):
origins[ii] = -origins[ii]
if not weights.shape[ii] & 1:
origins[ii] -= 1
for origin, lenw in zip(origins, wshape):
if (lenw // 2 + origin < 0) or (lenw // 2 + origin > lenw):
raise ValueError('invalid origin')
if not weights.flags.contiguous:
weights = weights.copy()
output, return_value = _ni_support._get_output(output, input)
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.correlate(input, weights, output, mode, cval, origins)
return return_value
@docfiller
def correlate(input, weights, output=None, mode='reflect', cval=0.0,
origin=0):
"""
Multi-dimensional correlation.
The array is correlated with the given kernel.
Parameters
----------
input : array-like
input array to filter
weights : ndarray
array of weights, same number of dimensions as input
output : array, optional
The ``output`` parameter passes an array in which to store the
filter output.
mode : {'reflect','constant','nearest','mirror', 'wrap'}, optional
The ``mode`` parameter determines how the array borders are
handled, where ``cval`` is the value when mode is equal to
'constant'. Default is 'reflect'
cval : scalar, optional
Value to fill past edges of input if ``mode`` is 'constant'. Default
is 0.0
origin : scalar, optional
The ``origin`` parameter controls the placement of the filter.
Default 0
See Also
--------
convolve : Convolve an image with a kernel.
"""
return _correlate_or_convolve(input, weights, output, mode, cval,
origin, False)
@docfiller
def convolve(input, weights, output=None, mode='reflect', cval=0.0,
origin=0):
"""
Multidimensional convolution.
The array is convolved with the given kernel.
Parameters
----------
input : array_like
Input array to filter.
weights : array_like
Array of weights, same number of dimensions as input
output : ndarray, optional
The `output` parameter passes an array in which to store the
filter output.
mode : {'reflect','constant','nearest','mirror', 'wrap'}, optional
the `mode` parameter determines how the array borders are
handled. For 'constant' mode, values beyond borders are set to be
`cval`. Default is 'reflect'.
cval : scalar, optional
Value to fill past edges of input if `mode` is 'constant'. Default
is 0.0
origin : array_like, optional
The `origin` parameter controls the placement of the filter.
Default is 0.
Returns
-------
result : ndarray
The result of convolution of `input` with `weights`.
See Also
--------
correlate : Correlate an image with a kernel.
Notes
-----
Each value in result is :math:`C_i = \\sum_j{I_{i+j-k} W_j}`, where
W is the `weights` kernel,
j is the n-D spatial index over :math:`W`,
I is the `input` and k is the coordinate of the center of
W, specified by `origin` in the input parameters.
Examples
--------
Perhaps the simplest case to understand is ``mode='constant', cval=0.0``,
because in this case borders (i.e. where the `weights` kernel, centered
on any one value, extends beyond an edge of `input`.
>>> a = np.array([[1, 2, 0, 0],
.... [5, 3, 0, 4],
.... [0, 0, 0, 7],
.... [9, 3, 0, 0]])
>>> k = np.array([[1,1,1],[1,1,0],[1,0,0]])
>>> from scipy import ndimage
>>> ndimage.convolve(a, k, mode='constant', cval=0.0)
array([[11, 10, 7, 4],
[10, 3, 11, 11],
[15, 12, 14, 7],
[12, 3, 7, 0]])
Setting ``cval=1.0`` is equivalent to padding the outer edge of `input`
with 1.0's (and then extracting only the original region of the result).
>>> ndimage.convolve(a, k, mode='constant', cval=1.0)
array([[13, 11, 8, 7],
[11, 3, 11, 14],
[16, 12, 14, 10],
[15, 6, 10, 5]])
With ``mode='reflect'`` (the default), outer values are reflected at the
edge of `input` to fill in missing values.
>>> b = np.array([[2, 0, 0],
[1, 0, 0],
[0, 0, 0]])
>>> k = np.array([[0,1,0],[0,1,0],[0,1,0]])
>>> ndimage.convolve(b, k, mode='reflect')
array([[5, 0, 0],
[3, 0, 0],
[1, 0, 0]])
This includes diagonally at the corners.
>>> k = np.array([[1,0,0],[0,1,0],[0,0,1]])
>>> ndimage.convolve(b, k)
array([[4, 2, 0],
[3, 2, 0],
[1, 1, 0]])
With ``mode='nearest'``, the single nearest value in to an edge in
`input` is repeated as many times as needed to match the overlapping
`weights`.
>>> c = np.array([[2, 0, 1],
[1, 0, 0],
[0, 0, 0]])
>>> k = np.array([[0, 1, 0],
[0, 1, 0],
[0, 1, 0],
[0, 1, 0],
[0, 1, 0]])
>>> ndimage.convolve(c, k, mode='nearest')
array([[7, 0, 3],
[5, 0, 2],
[3, 0, 1]])
"""
return _correlate_or_convolve(input, weights, output, mode, cval,
origin, True)
@docfiller
def uniform_filter1d(input, size, axis=-1, output=None,
mode="reflect", cval=0.0, origin=0):
"""Calculate a one-dimensional uniform filter along the given axis.
The lines of the array along the given axis are filtered with a
uniform filter of given size.
Parameters
----------
%(input)s
size : integer
length of uniform filter
%(axis)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
"""
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
axis = _ni_support._check_axis(axis, input.ndim)
if size < 1:
raise RuntimeError('incorrect filter size')
output, return_value = _ni_support._get_output(output, input)
if (size // 2 + origin < 0) or (size // 2 + origin >= size):
raise ValueError('invalid origin')
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.uniform_filter1d(input, size, axis, output, mode, cval,
origin)
return return_value
@docfiller
def uniform_filter(input, size=3, output=None, mode="reflect",
cval=0.0, origin=0):
"""Multi-dimensional uniform filter.
Parameters
----------
%(input)s
size : int or sequence of ints
The sizes of the uniform filter are given for each axis as a
sequence, or as a single number, in which case the size is
equal for all axes.
%(output)s
%(mode)s
%(cval)s
%(origin)s
Notes
-----
The multi-dimensional filter is implemented as a sequence of
one-dimensional uniform filters. The intermediate arrays are stored
in the same data type as the output. Therefore, for output types
with a limited precision, the results may be imprecise because
intermediate results may be stored with insufficient precision.
"""
input = numpy.asarray(input)
output, return_value = _ni_support._get_output(output, input)
sizes = _ni_support._normalize_sequence(size, input.ndim)
origins = _ni_support._normalize_sequence(origin, input.ndim)
axes = list(range(input.ndim))
axes = [(axes[ii], sizes[ii], origins[ii])
for ii in range(len(axes)) if sizes[ii] > 1]
if len(axes) > 0:
for axis, size, origin in axes:
uniform_filter1d(input, int(size), axis, output, mode,
cval, origin)
input = output
else:
output[...] = input[...]
return return_value
@docfiller
def minimum_filter1d(input, size, axis=-1, output=None,
mode="reflect", cval=0.0, origin=0):
"""Calculate a one-dimensional minimum filter along the given axis.
The lines of the array along the given axis are filtered with a
minimum filter of given size.
Parameters
----------
%(input)s
size : int
length along which to calculate 1D minimum
%(axis)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
Notes
-----
This function implements the MINLIST algorithm [1]_, as described by
Richard Harter [2]_, and has a guaranteed O(n) performance, `n` being
the `input` length, regardless of filter size.
References
----------
.. [1] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.42.2777
.. [2] http://www.richardhartersworld.com/cri/2001/slidingmin.html
"""
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
axis = _ni_support._check_axis(axis, input.ndim)
if size < 1:
raise RuntimeError('incorrect filter size')
output, return_value = _ni_support._get_output(output, input)
if (size // 2 + origin < 0) or (size // 2 + origin >= size):
raise ValueError('invalid origin')
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.min_or_max_filter1d(input, size, axis, output, mode, cval,
origin, 1)
return return_value
@docfiller
def maximum_filter1d(input, size, axis=-1, output=None,
mode="reflect", cval=0.0, origin=0):
"""Calculate a one-dimensional maximum filter along the given axis.
The lines of the array along the given axis are filtered with a
maximum filter of given size.
Parameters
----------
%(input)s
size : int
Length along which to calculate the 1-D maximum.
%(axis)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
Returns
-------
maximum1d : ndarray, None
Maximum-filtered array with same shape as input.
None if `output` is not None
Notes
-----
This function implements the MAXLIST algorithm [1]_, as described by
Richard Harter [2]_, and has a guaranteed O(n) performance, `n` being
the `input` length, regardless of filter size.
References
----------
.. [1] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.42.2777
.. [2] http://www.richardhartersworld.com/cri/2001/slidingmin.html
"""
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
axis = _ni_support._check_axis(axis, input.ndim)
if size < 1:
raise RuntimeError('incorrect filter size')
output, return_value = _ni_support._get_output(output, input)
if (size // 2 + origin < 0) or (size // 2 + origin >= size):
raise ValueError('invalid origin')
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.min_or_max_filter1d(input, size, axis, output, mode, cval,
origin, 0)
return return_value
def _min_or_max_filter(input, size, footprint, structure, output, mode,
cval, origin, minimum):
if structure is None:
if footprint is None:
if size is None:
raise RuntimeError("no footprint provided")
separable = True
else:
footprint = numpy.asarray(footprint)
footprint = footprint.astype(bool)
if numpy.alltrue(numpy.ravel(footprint), axis=0):
size = footprint.shape
footprint = None
separable = True
else:
separable = False
else:
structure = numpy.asarray(structure, dtype=numpy.float64)
separable = False
if footprint is None:
footprint = numpy.ones(structure.shape, bool)
else:
footprint = numpy.asarray(footprint)
footprint = footprint.astype(bool)
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
output, return_value = _ni_support._get_output(output, input)
origins = _ni_support._normalize_sequence(origin, input.ndim)
if separable:
sizes = _ni_support._normalize_sequence(size, input.ndim)
axes = list(range(input.ndim))
axes = [(axes[ii], sizes[ii], origins[ii])
for ii in range(len(axes)) if sizes[ii] > 1]
if minimum:
filter_ = minimum_filter1d
else:
filter_ = maximum_filter1d
if len(axes) > 0:
for axis, size, origin in axes:
filter_(input, int(size), axis, output, mode, cval, origin)
input = output
else:
output[...] = input[...]
else:
fshape = [ii for ii in footprint.shape if ii > 0]
if len(fshape) != input.ndim:
raise RuntimeError('footprint array has incorrect shape.')
for origin, lenf in zip(origins, fshape):
if (lenf // 2 + origin < 0) or (lenf // 2 + origin >= lenf):
raise ValueError('invalid origin')
if not footprint.flags.contiguous:
footprint = footprint.copy()
if structure is not None:
if len(structure.shape) != input.ndim:
raise RuntimeError('structure array has incorrect shape')
if not structure.flags.contiguous:
structure = structure.copy()
mode = _ni_support._extend_mode_to_code(mode)
_nd_image.min_or_max_filter(input, footprint, structure, output,
mode, cval, origins, minimum)
return return_value
@docfiller
def minimum_filter(input, size=None, footprint=None, output=None,
mode="reflect", cval=0.0, origin=0):
"""Calculates a multi-dimensional minimum filter.
Parameters
----------
%(input)s
%(size_foot)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
"""
return _min_or_max_filter(input, size, footprint, None, output, mode,
cval, origin, 1)
@docfiller
def maximum_filter(input, size=None, footprint=None, output=None,
mode="reflect", cval=0.0, origin=0):
"""Calculates a multi-dimensional maximum filter.
Parameters
----------
%(input)s
%(size_foot)s
%(output)s
%(mode)s
%(cval)s
%(origin)s
"""
return _min_or_max_filter(input, size, footprint, None, output, mode,
cval, origin, 0)
@docfiller
def _rank_filter(input, rank, size=None, footprint=None, output=None,
mode="reflect", cval=0.0, origin=0, operation='rank'):
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError('Complex type not supported')
origins = _ni_support._normalize_sequence(origin, input.ndim)
if footprint is None:
if size is None:
raise RuntimeError("no footprint or filter size provided")
sizes = _ni_support._normalize_sequence(size, input.ndim)
footprint = numpy.ones(sizes, dtype=bool)
else:
footprint = numpy.asarray(footprint, dtype=bool)
fshape = [ii for ii in footprint.shape if ii > 0]
if len(fshape) != input.ndim:
raise RuntimeError('filter footprint array has incorrect shape.')
for origin, lenf in zip(origins, fshape):
if (lenf // 2 + origin < 0) or (lenf // 2 + origin >= lenf):
raise ValueError('invalid origin')
if not footprint.flags.contiguous:
footprint = footprint.copy()
filter_size = numpy.where(footprint, 1, 0).sum()
if operation == 'median':
rank = filter_size // 2
elif operation == 'percentile':
percentile = rank
if percentile < 0.0:
percentile += 100.0