# Copyright (C) 2003-2005 Peter J. Verveer
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import numpy
import _ni_support
import _nd_image
import filters
def _center_is_true(structure, origin):
structure = numpy.array(structure)
coor = tuple([oo + ss // 2 for ss, oo in zip(structure.shape,
origin)])
return bool(structure[coor])
def iterate_structure(structure, iterations, origin = None):
"""
Iterate a structure by dilating it with itself.
Parameters
----------
structure : array_like
Structuring element (an array of bools, for example), to be dilated with
itself.
iterations : int
number of dilations performed on the structure with itself
origin : optional
If origin is None, only the iterated structure is returned. If
not, a tuple of the iterated structure and the modified origin is
returned.
Returns
-------
output: ndarray of bools
A new structuring element obtained by dilating `structure`
(`iterations` - 1) times with itself.
See also
--------
generate_binary_structure
Examples
--------
>>> struct = ndimage.generate_binary_structure(2, 1)
>>> struct.astype(int)
array([[0, 1, 0],
[1, 1, 1],
[0, 1, 0]])
>>> ndimage.iterate_structure(struct, 2).astype(int)
array([[0, 0, 1, 0, 0],
[0, 1, 1, 1, 0],
[1, 1, 1, 1, 1],
[0, 1, 1, 1, 0],
[0, 0, 1, 0, 0]])
>>> ndimage.iterate_structure(struct, 3).astype(int)
array([[0, 0, 0, 1, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 1, 1, 1, 1, 1, 0],
[1, 1, 1, 1, 1, 1, 1],
[0, 1, 1, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 0, 1, 0, 0, 0]])
"""
structure = numpy.asarray(structure)
if iterations < 2:
return structure.copy()
ni = iterations - 1
shape = [ii + ni * (ii - 1) for ii in structure.shape]
pos = [ni * (structure.shape[ii] / 2) for ii in range(len(shape))]
slc = [slice(pos[ii], pos[ii] + structure.shape[ii], None)
for ii in range(len(shape))]
out = numpy.zeros(shape, bool)
out[slc] = structure != 0
out = binary_dilation(out, structure, iterations = ni)
if origin is None:
return out
else:
origin = _ni_support._normalize_sequence(origin, structure.ndim)
origin = [iterations * o for o in origin]
return out, origin
def generate_binary_structure(rank, connectivity):
"""
Generate a binary structure for binary morphological operations.
Parameters
----------
rank : int
Number of dimensions of the array to which the structuring element
will be applied, as returned by `np.ndim`.
connectivity : int
`connectivity` determines which elements of the output array belong
to the structure, i.e. are considered as neighbors of the central
element. Elements up to a squared distance of `connectivity` from
the center are considered neighbors. `connectivity` may range from 1
(no diagonal elements are neighbors) to `rank` (all elements are
neighbors).
Returns
-------
output : ndarray of bools
Structuring element which may be used for binary morphological
operations, with `rank` dimensions and all dimensions equal to 3.
See also
--------
iterate_structure, binary_dilation, binary_erosion
Notes
-----
`generate_binary_structure` can only create structuring elements with
dimensions equal to 3, i.e. minimal dimensions. For larger structuring
elements, that are useful e.g. for eroding large objects, one may either
use `iterate_structure`, or create directly custom arrays with
numpy functions such as `numpy.ones`.
Examples
--------
>>> struct = ndimage.generate_binary_structure(2, 1)
>>> struct
array([[False, True, False],
[ True, True, True],
[False, True, False]], dtype=bool)
>>> a = np.zeros((5,5))
>>> a[2, 2] = 1
>>> a
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.]])
>>> b = ndimage.binary_dilation(a, structure=struct).astype(a.dtype)
>>> b
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 0., 0., 0., 0.]])
>>> ndimage.binary_dilation(b, structure=struct).astype(a.dtype)
array([[ 0., 0., 1., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 1., 1., 1., 1., 1.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 1., 0., 0.]])
>>> struct = ndimage.generate_binary_structure(2, 2)
>>> struct
array([[ True, True, True],
[ True, True, True],
[ True, True, True]], dtype=bool)
>>> struct = ndimage.generate_binary_structure(3, 1)
>>> struct # no diagonal elements
array([[[False, False, False],
[False, True, False],
[False, False, False]],
[[False, True, False],
[ True, True, True],
[False, True, False]],
[[False, False, False],
[False, True, False],
[False, False, False]]], dtype=bool)
"""
if connectivity < 1:
connectivity = 1
if rank < 1:
if connectivity < 1:
return numpy.array(0, dtype = bool)
else:
return numpy.array(1, dtype = bool)
output = numpy.fabs(numpy.indices([3] * rank) - 1)
output = numpy.add.reduce(output, 0)
return numpy.asarray(output <= connectivity, dtype = bool)
def _binary_erosion(input, structure, iterations, mask, output,
border_value, origin, invert, brute_force):
input = numpy.asarray(input)
if numpy.iscomplexobj(input):
raise TypeError, 'Complex type not supported'
if structure is None:
structure = generate_binary_structure(input.ndim, 1)
else:
structure = numpy.asarray(structure)
structure = structure.astype(bool)
if structure.ndim != input.ndim:
raise RuntimeError, 'structure rank must equal input rank'
if not structure.flags.contiguous:
structure = structure.copy()
if numpy.product(structure.shape,axis=0) < 1:
raise RuntimeError, 'structure must not be empty'
if mask is not None:
mask = numpy.asarray(mask)
if mask.shape != input.shape:
raise RuntimeError, 'mask and input must have equal sizes'
origin = _ni_support._normalize_sequence(origin, input.ndim)
cit = _center_is_true(structure, origin)
if isinstance(output, numpy.ndarray):
if numpy.iscomplexobj(output):
raise TypeError, 'Complex output type not supported'
else:
output = bool
output, return_value = _ni_support._get_output(output, input)
if iterations == 1:
_nd_image.binary_erosion(input, structure, mask, output,
border_value, origin, invert, cit, 0)
return return_value
elif cit and not brute_force:
changed, coordinate_list = _nd_image.binary_erosion(input,
structure, mask, output, border_value, origin, invert, cit, 1)
structure = structure[tuple([slice(None, None, -1)] *
structure.ndim)]
for ii in range(len(origin)):
origin[ii] = -origin[ii]
if not structure.shape[ii] & 1:
origin[ii] -= 1
if mask is not None:
msk = numpy.asarray(mask)
msk = mask.astype(numpy.int8)
if msk is mask:
msk = mask.copy()
mask = msk
if not structure.flags.contiguous:
structure = structure.copy()
_nd_image.binary_erosion2(output, structure, mask, iterations - 1,
origin, invert, coordinate_list)
return return_value
else:
tmp_in = numpy.zeros(input.shape, bool)
if return_value is None:
tmp_out = output
else:
tmp_out = numpy.zeros(input.shape, bool)
if not iterations & 1:
tmp_in, tmp_out = tmp_out, tmp_in
changed = _nd_image.binary_erosion(input, structure, mask,
tmp_out, border_value, origin, invert, cit, 0)
ii = 1
while (ii < iterations) or (iterations < 1) and changed:
tmp_in, tmp_out = tmp_out, tmp_in
changed = _nd_image.binary_erosion(tmp_in, structure, mask,
tmp_out, border_value, origin, invert, cit, 0)
ii += 1
if return_value is not None:
return tmp_out
def binary_erosion(input, structure = None, iterations = 1, mask = None,
output = None, border_value = 0, origin = 0, brute_force = False):
"""
Multi-dimensional binary erosion with a given structuring element.
Binary erosion is a mathematical morphology operation used for image
processing.
Parameters
----------
input : array_like
Binary image to be eroded. Non-zero (True) elements form
the subset to be eroded.
structure : array_like, optional
Structuring element used for the erosion. Non-zero elements are
considered True. If no structuring element is provided, an element
is generated with a square connectivity equal to one.
iterations : {int, float}, optional
The erosion is repeated `iterations` times (one, by default).
If iterations is less than 1, the erosion is repeated until the
result does not change anymore.
mask : array_like, optional
If a mask is given, only those elements with a True value at
the corresponding mask element are modified at each iteration.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin: int or tuple of ints, optional
Placement of the filter, by default 0.
border_value: int (cast to 0 or 1)
Value at the border in the output array.
Returns
-------
out: ndarray of bools
Erosion of the input by the structuring element.
See also
--------
grey_erosion, binary_dilation, binary_closing, binary_opening,
generate_binary_structure
Notes
-----
Erosion [1]_ is a mathematical morphology operation [2]_ that uses a
structuring element for shrinking the shapes in an image. The binary
erosion of an image by a structuring element is the locus of the points
where a superimposition of the structuring element centered on the point
is entirely contained in the set of non-zero elements of the image.
References
----------
.. [1] http://en.wikipedia.org/wiki/Erosion_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[1:6, 2:5] = 1
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.binary_erosion(a).astype(a.dtype)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> #Erosion removes objects smaller than the structure
>>> ndimage.binary_erosion(a, structure=np.ones((5,5))).astype(a.dtype)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
"""
return _binary_erosion(input, structure, iterations, mask,
output, border_value, origin, 0, brute_force)
def binary_dilation(input, structure = None, iterations = 1, mask = None,
output = None, border_value = 0, origin = 0, brute_force = False):
"""
Multi-dimensional binary dilation with the given structuring element.
Parameters
----------
input : array_like
Binary array_like to be dilated. Non-zero (True) elements form
the subset to be dilated.
structure : array_like, optional
Structuring element used for the dilation. Non-zero elements are
considered True. If no structuring element is provided an element
is generated with a square connectivity equal to one.
iterations : {int, float}, optional
The dilation is repeated `iterations` times (one, by default).
If iterations is less than 1, the dilation is repeated until the
result does not change anymore.
mask : array_like, optional
If a mask is given, only those elements with a True value at
the corresponding mask element are modified at each iteration.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin : int or tuple of ints, optional
Placement of the filter, by default 0.
border_value : int (cast to 0 or 1)
Value at the border in the output array.
Returns
-------
out : ndarray of bools
Dilation of the input by the structuring element.
See also
--------
grey_dilation, binary_erosion, binary_closing, binary_opening,
generate_binary_structure
Notes
-----
Dilation [1]_ is a mathematical morphology operation [2]_ that uses a
structuring element for expanding the shapes in an image. The binary
dilation of an image by a structuring element is the locus of the points
covered by the structuring element, when its center lies within the
non-zero points of the image.
References
----------
.. [1] http://en.wikipedia.org/wiki/Dilation_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((5, 5))
>>> a[2, 2] = 1
>>> a
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.]])
>>> ndimage.binary_dilation(a)
array([[False, False, False, False, False],
[False, False, True, False, False],
[False, True, True, True, False],
[False, False, True, False, False],
[False, False, False, False, False]], dtype=bool)
>>> ndimage.binary_dilation(a).astype(a.dtype)
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 0., 0., 0., 0.]])
>>> # 3x3 structuring element with connectivity 1, used by default
>>> struct1 = ndimage.generate_binary_structure(2, 1)
>>> struct1
array([[False, True, False],
[ True, True, True],
[False, True, False]], dtype=bool)
>>> # 3x3 structuring element with connectivity 2
>>> struct2 = ndimage.generate_binary_structure(2, 2)
>>> struct2
array([[ True, True, True],
[ True, True, True],
[ True, True, True]], dtype=bool)
>>> ndimage.binary_dilation(a, structure=struct1).astype(a.dtype)
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 1., 0., 0.],
[ 0., 0., 0., 0., 0.]])
>>> ndimage.binary_dilation(a, structure=struct2).astype(a.dtype)
array([[ 0., 0., 0., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 0., 0., 0.]])
>>> ndimage.binary_dilation(a, structure=struct1,\\
... iterations=2).astype(a.dtype)
array([[ 0., 0., 1., 0., 0.],
[ 0., 1., 1., 1., 0.],
[ 1., 1., 1., 1., 1.],
[ 0., 1., 1., 1., 0.],
[ 0., 0., 1., 0., 0.]])
"""
input = numpy.asarray(input)
if structure is None:
structure = generate_binary_structure(input.ndim, 1)
origin = _ni_support._normalize_sequence(origin, input.ndim)
structure = numpy.asarray(structure)
structure = structure[tuple([slice(None, None, -1)] *
structure.ndim)]
for ii in range(len(origin)):
origin[ii] = -origin[ii]
if not structure.shape[ii] & 1:
origin[ii] -= 1
return _binary_erosion(input, structure, iterations, mask,
output, border_value, origin, 1, brute_force)
def binary_opening(input, structure = None, iterations = 1, output = None,
origin = 0):
"""
Multi-dimensional binary opening with the given structuring element.
The *opening* of an input image by a structuring element is the
*dilation* of the *erosion* of the image by the structuring element.
Parameters
----------
input : array_like
Binary array_like to be opened. Non-zero (True) elements form
the subset to be opened.
structure : array_like, optional
Structuring element used for the opening. Non-zero elements are
considered True. If no structuring element is provided an element
is generated with a square connectivity equal to one (i.e., only
nearest neighbors are connected to the center, diagonally-connected
elements are not considered neighbors).
iterations : {int, float}, optional
The erosion step of the opening, then the dilation step are each
repeated `iterations` times (one, by default). If `iterations` is
less than 1, each operation is repeated until the result does
not change anymore.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin : int or tuple of ints, optional
Placement of the filter, by default 0.
Returns
-------
out : ndarray of bools
Opening of the input by the structuring element.
See also
--------
grey_opening, binary_closing, binary_erosion, binary_dilation,
generate_binary_structure
Notes
-----
*Opening* [1]_ is a mathematical morphology operation [2]_ that
consists in the succession of an erosion and a dilation of the
input with the same structuring element. Opening therefore removes
objects smaller than the structuring element.
Together with *closing* (`binary_closing`), opening can be used for
noise removal.
References
----------
.. [1] http://en.wikipedia.org/wiki/Opening_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((5,5), dtype=np.int)
>>> a[1:4, 1:4] = 1; a[4, 4] = 1
>>> a
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 1]])
>>> # Opening removes small objects
>>> ndimage.binary_opening(a, structure=np.ones((3,3))).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> # Opening can also smooth corners
>>> ndimage.binary_opening(a).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 0, 1, 0, 0],
[0, 1, 1, 1, 0],
[0, 0, 1, 0, 0],
[0, 0, 0, 0, 0]])
>>> # Opening is the dilation of the erosion of the input
>>> ndimage.binary_erosion(a).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 0, 0, 0, 0],
[0, 0, 1, 0, 0],
[0, 0, 0, 0, 0],
[0, 0, 0, 0, 0]])
>>> ndimage.binary_dilation(ndimage.binary_erosion(a)).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 0, 1, 0, 0],
[0, 1, 1, 1, 0],
[0, 0, 1, 0, 0],
[0, 0, 0, 0, 0]])
"""
input = numpy.asarray(input)
if structure is None:
rank = input.ndim
structure = generate_binary_structure(rank, 1)
tmp = binary_erosion(input, structure, iterations, None, None, 0,
origin)
return binary_dilation(tmp, structure, iterations, None, output, 0,
origin)
def binary_closing(input, structure = None, iterations = 1, output = None,
origin = 0):
"""
Multi-dimensional binary closing with the given structuring element.
The *closing* of an input image by a structuring element is the
*erosion* of the *dilation* of the image by the structuring element.
Parameters
----------
input : array_like
Binary array_like to be closed. Non-zero (True) elements form
the subset to be closed.
structure : array_like, optional
Structuring element used for the closing. Non-zero elements are
considered True. If no structuring element is provided an element
is generated with a square connectivity equal to one (i.e., only
nearest neighbors are connected to the center, diagonally-connected
elements are not considered neighbors).
iterations : {int, float}, optional
The dilation step of the closing, then the erosion step are each
repeated `iterations` times (one, by default). If iterations is
less than 1, each operations is repeated until the result does
not change anymore.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin : int or tuple of ints, optional
Placement of the filter, by default 0.
Returns
-------
out : ndarray of bools
Closing of the input by the structuring element.
See also
--------
grey_closing, binary_opening, binary_dilation, binary_erosion,
generate_binary_structure
Notes
-----
*Closing* [1]_ is a mathematical morphology operation [2]_ that
consists in the succession of a dilation and an erosion of the
input with the same structuring element. Closing therefore fills
holes smaller than the structuring element.
Together with *opening* (`binary_opening`), closing can be used for
noise removal.
References
----------
.. [1] http://en.wikipedia.org/wiki/Closing_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((5,5), dtype=np.int)
>>> a[1:-1, 1:-1] = 1; a[2,2] = 0
>>> a
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 0, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> # Closing removes small holes
>>> ndimage.binary_closing(a).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> # Closing is the erosion of the dilation of the input
>>> ndimage.binary_dilation(a).astype(np.int)
array([[0, 1, 1, 1, 0],
[1, 1, 1, 1, 1],
[1, 1, 1, 1, 1],
[1, 1, 1, 1, 1],
[0, 1, 1, 1, 0]])
>>> ndimage.binary_erosion(ndimage.binary_dilation(a)).astype(np.int)
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[1:6, 2:5] = 1; a[1:3,3] = 0
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0],
[0, 0, 1, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> # In addition to removing holes, closing can also
>>> # coarsen boundaries with fine hollows.
>>> ndimage.binary_closing(a).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.binary_closing(a, structure=np.ones((2,2))).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
"""
input = numpy.asarray(input)
if structure is None:
rank = input.ndim
structure = generate_binary_structure(rank, 1)
tmp = binary_dilation(input, structure, iterations, None, None, 0,
origin)
return binary_erosion(tmp, structure, iterations, None, output, 0,
origin)
def binary_hit_or_miss(input, structure1 = None, structure2 = None,
output = None, origin1 = 0, origin2 = None):
"""
Multi-dimensional binary hit-or-miss transform.
The hit-or-miss transform finds the locations of a given pattern
inside the input image.
Parameters
----------
input : array_like (cast to booleans)
Binary image where a pattern is to be detected.
structure1 : array_like (cast to booleans), optional
Part of the structuring element to be fitted to the foreground
(non-zero elements) of `input`. If no value is provided, a
structure of square connectivity 1 is chosen.
structure2 : array_like (cast to booleans), optional
Second part of the structuring element that has to miss completely
the foreground. If no value is provided, the complementary of
`structure1` is taken.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin1 : int or tuple of ints, optional
Placement of the first part of the structuring element `structure1`,
by default 0 for a centered structure.
origin2 : int or tuple of ints, optional
Placement of the second part of the structuring element `structure2`,
by default 0 for a centered structure. If a value is provided for
`origin1` and not for `origin2`, then `origin2` is set to `origin1`.
Returns
-------
output : ndarray
Hit-or-miss transform of `input` with the given structuring
element (`structure1`, `structure2`).
See also
--------
ndimage.morphology, binary_erosion
Notes
-----
References
----------
.. [1] http://en.wikipedia.org/wiki/Hit-or-miss_transform
Examples
--------
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[1, 1] = 1; a[2:4, 2:4] = 1; a[4:6, 4:6] = 1
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 0, 0, 0],
[0, 0, 1, 1, 0, 0, 0],
[0, 0, 0, 0, 1, 1, 0],
[0, 0, 0, 0, 1, 1, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> structure1 = np.array([[1, 0, 0], [0, 1, 1], [0, 1, 1]])
>>> structure1
array([[1, 0, 0],
[0, 1, 1],
[0, 1, 1]])
>>> # Find the matches of structure1 in the array a
>>> ndimage.binary_hit_or_miss(a, structure1=structure1).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> # Change the origin of the filter
>>> # origin1=1 is equivalent to origin1=(1,1) here
>>> ndimage.binary_hit_or_miss(a, structure1=structure1,\\
... origin1=1).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 0, 0, 0]])
"""
input = numpy.asarray(input)
if structure1 is None:
structure1 = generate_binary_structure(input.ndim, 1)
if structure2 is None:
structure2 = numpy.logical_not(structure1)
origin1 = _ni_support._normalize_sequence(origin1, input.ndim)
if origin2 is None:
origin2 = origin1
else:
origin2 = _ni_support._normalize_sequence(origin2, input.ndim)
tmp1 = _binary_erosion(input, structure1, 1, None, None, 0, origin1,
0, False)
inplace = isinstance(output, numpy.ndarray)
result = _binary_erosion(input, structure2, 1, None, output, 0,
origin2, 1, False)
if inplace:
numpy.logical_not(output, output)
numpy.logical_and(tmp1, output, output)
else:
numpy.logical_not(result, result)
return numpy.logical_and(tmp1, result)
def binary_propagation(input, structure = None, mask = None,
output = None, border_value = 0, origin = 0):
"""
Multi-dimensional binary propagation with the given structuring element.
Parameters
----------
input : array_like
Binary image to be propagated inside `mask`.
structure : array_like
Structuring element used in the successive dilations. The output
may depend on the structuring element, especially if `mask` has
several connex components. If no structuring element is
provided, an element is generated with a squared connectivity equal
to one.
mask : array_like
Binary mask defining the region into which `input` is allowed to
propagate.
output : ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin : int or tuple of ints, optional
Placement of the filter, by default 0.
Returns
-------
ouput : ndarray
Binary propagation of `input` inside `mask`.
Notes
-----
This function is functionally equivalent to calling binary_dilation
with the number of iterations less then one: iterative dilation until
the result does not change anymore.
The succession of an erosion and propagation inside the original image
can be used instead of an *opening* for deleting small objects while
keeping the contours of larger objects untouched.
References
----------
.. [1] http://cmm.ensmp.fr/~serra/cours/pdf/en/ch6en.pdf, slide 15.
.. [2] http://www.qi.tnw.tudelft.nl/Courses/FIP/noframes/fip-Morpholo.html#Heading102
Examples
--------
>>> input = np.zeros((8, 8), dtype=np.int)
>>> input[2, 2] = 1
>>> mask = np.zeros((8, 8), dtype=np.int)
>>> mask[1:4, 1:4] = mask[4, 4] = mask[6:8, 6:8] = 1
>>> input
array([[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0]])
>>> mask
array([[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 1, 1],
[0, 0, 0, 0, 0, 0, 1, 1]])
>>> ndimage.binary_propagation(input, mask=mask).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.binary_propagation(input, mask=mask,\\
... structure=np.ones((3,3))).astype(np.int)
array([[0, 0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 1, 1, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0]])
>>> # Comparison between opening and erosion+propagation
>>> a = np.zeros((6,6), dtype=np.int)
>>> a[2:5, 2:5] = 1; a[0, 0] = 1; a[5, 5] = 1
>>> a
array([[1, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 0, 0, 0, 1]])
>>> ndimage.binary_opening(a).astype(np.int)
array([[0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 0, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 0]])
>>> b = ndimage.binary_erosion(a)
>>> b.astype(int)
array([[0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0]])
>>> ndimage.binary_propagation(b, mask=a).astype(np.int)
array([[0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 1, 1, 1, 0],
[0, 0, 0, 0, 0, 0]])
"""
return binary_dilation(input, structure, -1, mask, output,
border_value, origin)
def binary_fill_holes(input, structure = None, output = None, origin = 0):
"""
Fill the holes in binary objects.
Parameters
----------
input: array_like
n-dimensional binary array with holes to be filled
structure: array_like, optional
Structuring element used in the computation; large-size elements
make computations faster but may miss holes separated from the
background by thin regions. The default element (with a square
connectivity equal to one) yields the intuitive result where all
holes in the input have been filled.
output: ndarray, optional
Array of the same shape as input, into which the output is placed.
By default, a new array is created.
origin: int, tuple of ints, optional
Position of the structuring element.
Returns
-------
out: ndarray
Transformation of the initial image `input` where holes have been
filled.
See also
--------
binary_dilation, binary_propagation, label
Notes
-----
The algorithm used in this function consists in invading the complementary
of the shapes in `input` from the outer boundary of the image,
using binary dilations. Holes are not connected to the boundary and are
therefore not invaded. The result is the complementary subset of the
invaded region.
References
----------
.. [1] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((5, 5), dtype=int)
>>> a[1:4, 1:4] = 1
>>> a[2,2] = 0
>>> a
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 0, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> ndimage.binary_fill_holes(a).astype(int)
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
>>> # Too big structuring element
>>> ndimage.binary_fill_holes(a, structure=np.ones((5,5))).astype(int)
array([[0, 0, 0, 0, 0],
[0, 1, 1, 1, 0],
[0, 1, 0, 1, 0],
[0, 1, 1, 1, 0],
[0, 0, 0, 0, 0]])
"""
mask = numpy.logical_not(input)
tmp = numpy.zeros(mask.shape, bool)
inplace = isinstance(output, numpy.ndarray)
if inplace:
binary_dilation(tmp, structure, -1, mask, output, 1, origin)
numpy.logical_not(output, output)
else:
output = binary_dilation(tmp, structure, -1, mask, None, 1,
origin)
numpy.logical_not(output, output)
return output
def grey_erosion(input, size = None, footprint = None, structure = None,
output = None, mode = "reflect", cval = 0.0, origin = 0):
"""
Calculate a greyscale erosion, using either a structuring element,
or a footprint corresponding to a flat structuring element.
Grayscale erosion is a mathematical morphology operation. For the
simple case of a full and flat structuring element, it can be viewed
as a minimum filter over a sliding window.
Parameters
----------
input : array_like
Array over which the grayscale erosion is to be computed.
size : tuple of ints
Shape of a flat and full structuring element used for the
grayscale erosion. Optional if `footprint` is provided.
footprint : array of ints, optional
Positions of non-infinite elements of a flat structuring element
used for the grayscale erosion. Non-zero values give the set of
neighbors of the center over which the minimum is chosen.
structure : array of ints, optional
Structuring element used for the grayscale erosion. `structure`
may be a non-flat structuring element.
output : array, optional
An array used for storing the ouput of the erosion may be provided.
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
Returns
-------
output : ndarray
Grayscale erosion of `input`.
See also
--------
binary_erosion, grey_dilation, grey_opening, grey_closing
generate_binary_structure
ndimage.minimum_filter
Notes
-----
The grayscale erosion of an image input by a structuring element s defined
over a domain E is given by:
(input+s)(x) = min {input(y) - s(x-y), for y in E}
In particular, for structuring elements defined as
s(y) = 0 for y in E, the grayscale erosion computes the minimum of the
input image inside a sliding window defined by E.
Grayscale erosion [1]_ is a *mathematical morphology* operation [2]_.
References
----------
.. [1] http://en.wikipedia.org/wiki/Erosion_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[1:6, 1:6] = 3
>>> a[4,4] = 2; a[2,3] = 1
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 3, 3, 3, 3, 3, 0],
[0, 3, 3, 1, 3, 3, 0],
[0, 3, 3, 3, 3, 3, 0],
[0, 3, 3, 3, 2, 3, 0],
[0, 3, 3, 3, 3, 3, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.grey_erosion(a, size=(3,3))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 3, 2, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> footprint = ndimage.generate_binary_structure(2, 1)
>>> footprint
array([[False, True, False],
[ True, True, True],
[False, True, False]], dtype=bool)
>>> # Diagonally-connected elements are not considered neighbors
>>> ndimage.grey_erosion(a, size=(3,3), footprint=footprint)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 3, 1, 2, 0, 0],
[0, 0, 3, 2, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
"""
return filters._min_or_max_filter(input, size, footprint, structure,
output, mode, cval, origin, 1)
def grey_dilation(input, size = None, footprint = None, structure = None,
output = None, mode = "reflect", cval = 0.0, origin = 0):
"""
Calculate a greyscale dilation, using either a structuring element,
or a footprint corresponding to a flat structuring element.
Grayscale dilation is a mathematical morphology operation. For the
simple case of a full and flat structuring element, it can be viewed
as a maximum filter over a sliding window.
Parameters
----------
input : array_like
Array over which the grayscale dilation is to be computed.
size : tuple of ints
Shape of a flat and full structuring element used for the
grayscale dilation. Optional if `footprint` is provided.
footprint : array of ints, optional
Positions of non-infinite elements of a flat structuring element
used for the grayscale dilation. Non-zero values give the set of
neighbors of the center over which the maximum is chosen.
structure : array of ints, optional
Structuring element used for the grayscale dilation. `structure`
may be a non-flat structuring element.
output : array, optional
An array used for storing the ouput of the dilation may be provided.
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
Returns
-------
output : ndarray
Grayscale dilation of `input`.
See also
--------
binary_dilation, grey_erosion, grey_closing, grey_opening
generate_binary_structure
ndimage.maximum_filter
Notes
-----
The grayscale dilation of an image input by a structuring element s defined
over a domain E is given by:
(input+s)(x) = max {input(y) + s(x-y), for y in E}
In particular, for structuring elements defined as
s(y) = 0 for y in E, the grayscale dilation computes the maximum of the
input image inside a sliding window defined by E.
Grayscale dilation [1]_ is a *mathematical morphology* operation [2]_.
References
----------
.. [1] http://en.wikipedia.org/wiki/Dilation_%28morphology%29
.. [2] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[2:5, 2:5] = 1
>>> a[4,4] = 2; a[2,3] = 3
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 3, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.grey_dilation(a, size=(3,3))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 3, 3, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.grey_dilation(a, footprint=np.ones((3,3)))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 3, 3, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> s = ndimage.generate_binary_structure(2,1)
>>> s
array([[False, True, False],
[ True, True, True],
[False, True, False]], dtype=bool)
>>> ndimage.grey_dilation(a, footprint=s)
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 3, 1, 0, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 1, 3, 2, 1, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 0, 1, 1, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.grey_dilation(a, size=(3,3), structure=np.ones((3,3)))
array([[1, 1, 1, 1, 1, 1, 1],
[1, 2, 4, 4, 4, 2, 1],
[1, 2, 4, 4, 4, 2, 1],
[1, 2, 4, 4, 4, 3, 1],
[1, 2, 2, 3, 3, 3, 1],
[1, 2, 2, 3, 3, 3, 1],
[1, 1, 1, 1, 1, 1, 1]])
"""
if structure is not None:
structure = numpy.asarray(structure)
structure = structure[tuple([slice(None, None, -1)] *
structure.ndim)]
if footprint is not None:
footprint = numpy.asarray(footprint)
footprint = footprint[tuple([slice(None, None, -1)] *
footprint.ndim)]
input = numpy.asarray(input)
origin = _ni_support._normalize_sequence(origin, input.ndim)
for ii in range(len(origin)):
origin[ii] = -origin[ii]
if footprint is not None:
sz = footprint.shape[ii]
else:
sz = size[ii]
if not sz & 1:
origin[ii] -= 1
return filters._min_or_max_filter(input, size, footprint, structure,
output, mode, cval, origin, 0)
def grey_opening(input, size = None, footprint = None, structure = None,
output = None, mode = "reflect", cval = 0.0, origin = 0):
"""
Multi-dimensional greyscale opening.
A greyscale opening consists in the succession of a greyscale erosion,
and a greyscale dilation.
Parameters
----------
input : array_like
Array over which the grayscale opening is to be computed.
size : tuple of ints
Shape of a flat and full structuring element used for the
grayscale opening. Optional if `footprint` is provided.
footprint : array of ints, optional
Positions of non-infinite elements of a flat structuring element
used for the grayscale opening.
structure : array of ints, optional
Structuring element used for the grayscale opening. `structure`
may be a non-flat structuring element.
output : array, optional
An array used for storing the ouput of the opening may be provided.
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
Returns
-------
output : ndarray
Result of the grayscale opening of `input` with `structure`.
See also
--------
binary_opening, grey_dilation, grey_erosion, grey_closing
generate_binary_structure
Notes
-----
The action of a grayscale opening with a flat structuring element amounts
to smoothen high local maxima, whereas binary opening erases small objects.
References
----------
.. [1] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.arange(36).reshape((6,6))
>>> a[3, 3] = 50
>>> a
array([[ 0, 1, 2, 3, 4, 5],
[ 6, 7, 8, 9, 10, 11],
[12, 13, 14, 15, 16, 17],
[18, 19, 20, 50, 22, 23],
[24, 25, 26, 27, 28, 29],
[30, 31, 32, 33, 34, 35]])
>>> ndimage.grey_opening(a, size=(3,3))
array([[ 0, 1, 2, 3, 4, 4],
[ 6, 7, 8, 9, 10, 10],
[12, 13, 14, 15, 16, 16],
[18, 19, 20, 22, 22, 22],
[24, 25, 26, 27, 28, 28],
[24, 25, 26, 27, 28, 28]])
>>> # Note that the local maximum a[3,3] has disappeared
"""
tmp = grey_erosion(input, size, footprint, structure, None, mode,
cval, origin)
return grey_dilation(tmp, size, footprint, structure, output, mode,
cval, origin)
def grey_closing(input, size = None, footprint = None, structure = None,
output = None, mode = "reflect", cval = 0.0, origin = 0):
"""
Multi-dimensional greyscale closing.
A greyscale closing consists in the succession of a greyscale dilation,
and a greyscale erosion.
Parameters
----------
input : array_like
Array over which the grayscale closing is to be computed.
size : tuple of ints
Shape of a flat and full structuring element used for the
grayscale closing. Optional if `footprint` is provided.
footprint : array of ints, optional
Positions of non-infinite elements of a flat structuring element
used for the grayscale closing.
structure : array of ints, optional
Structuring element used for the grayscale closing. `structure`
may be a non-flat structuring element.
output : array, optional
An array used for storing the ouput of the closing may be provided.
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
Returns
-------
output : ndarray
Result of the grayscale closing of `input` with `structure`.
See also
--------
binary_closing, grey_dilation, grey_erosion, grey_opening
generate_binary_structure
Notes
-----
The action of a grayscale closing with a flat structuring element amounts
to smoothen deep local minima, whereas binary closing fills small holes.
References
----------
.. [1] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.arange(36).reshape((6,6))
>>> a[3,3] = 0
>>> a
array([[ 0, 1, 2, 3, 4, 5],
[ 6, 7, 8, 9, 10, 11],
[12, 13, 14, 15, 16, 17],
[18, 19, 20, 0, 22, 23],
[24, 25, 26, 27, 28, 29],
[30, 31, 32, 33, 34, 35]])
>>> ndimage.grey_closing(a, size=(3,3))
array([[ 7, 7, 8, 9, 10, 11],
[ 7, 7, 8, 9, 10, 11],
[13, 13, 14, 15, 16, 17],
[19, 19, 20, 20, 22, 23],
[25, 25, 26, 27, 28, 29],
[31, 31, 32, 33, 34, 35]])
>>> # Note that the local minimum a[3,3] has disappeared
"""
tmp = grey_dilation(input, size, footprint, structure, None, mode,
cval, origin)
return grey_erosion(tmp, size, footprint, structure, output, mode,
cval, origin)
def morphological_gradient(input, size = None, footprint = None,
structure = None, output = None, mode = "reflect",
cval = 0.0, origin = 0):
"""
Multi-dimensional morphological gradient.
The morphological gradient is calculated as the difference between a
dilation and an erosion of the input with a given structuring element.
Parameters
----------
input : array_like
Array over which to compute the morphlogical gradient.
size : tuple of ints
Shape of a flat and full structuring element used for the
mathematical morphology operations. Optional if `footprint`
is provided. A larger `size` yields a more blurred gradient.
footprint : array of ints, optional
Positions of non-infinite elements of a flat structuring element
used for the morphology operations. Larger footprints
give a more blurred morphological gradient.
structure : array of ints, optional
Structuring element used for the morphology operations.
`structure` may be a non-flat structuring element.
output : array, optional
An array used for storing the ouput of the morphological gradient
may be provided.
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
Returns
-------
output : ndarray
Morphological gradient of `input`.
See also
--------
grey_dilation, grey_erosion
ndimage.gaussian_gradient_magnitude
Notes
-----
For a flat structuring element, the morphological gradient
computed at a given point corresponds to the maximal difference
between elements of the input among the elements covered by the
structuring element centered on the point.
References
----------
.. [1] http://en.wikipedia.org/wiki/Mathematical_morphology
Examples
--------
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[2:5, 2:5] = 1
>>> ndimage.morphological_gradient(a, size=(3,3))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 0, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> # The morphological gradient is computed as the difference
>>> # between a dilation and an erosion
>>> ndimage.grey_dilation(a, size=(3,3)) -\\
... ndimage.grey_erosion(a, size=(3,3))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 0, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 1, 1, 1, 1, 1, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> a = np.zeros((7,7), dtype=np.int)
>>> a[2:5, 2:5] = 1
>>> a[4,4] = 2; a[2,3] = 3
>>> a
array([[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 3, 1, 0, 0],
[0, 0, 1, 1, 1, 0, 0],
[0, 0, 1, 1, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0]])
>>> ndimage.morphological_gradient(a, size=(3,3))
array([[0, 0, 0, 0, 0, 0, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 3, 3, 1, 0],
[0, 1, 3, 2, 3, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 1, 1, 2, 2, 2, 0],
[0, 0, 0, 0, 0, 0, 0]])
"""
tmp = grey_dilation(input, size, footprint, structure, None, mode,
cval, origin)
if isinstance(output, numpy.ndarray):
grey_erosion(input, size, footprint, structure, output, mode,
cval, origin)
return numpy.subtract(tmp, output, output)
else:
return (tmp - grey_erosion(input, size, footprint, structure,
None, mode, cval, origin))
def morphological_laplace(input, size = None, footprint = None,
structure = None, output = None,
mode = "reflect", cval = 0.0, origin = 0):
"""Multi-dimensional morphological laplace.
Either a size or a footprint, or the structure must be provided. An
output array can optionally be provided. The origin parameter
controls the placement of the filter. The mode parameter
determines how the array borders are handled, where cval is the
value when mode is equal to 'constant'.
"""
tmp1 = grey_dilation(input, size, footprint, structure, None, mode,
cval, origin)
if isinstance(output, numpy.ndarray):
grey_erosion(input, size, footprint, structure, output, mode,
cval, origin)
numpy.add(tmp1, output, output)
del tmp1
numpy.subtract(output, input, output)
return numpy.subtract(output, input, output)
else:
tmp2 = grey_erosion(input, size, footprint, structure, None, mode,
cval, origin)
numpy.add(tmp1, tmp2, tmp2)
del tmp1
numpy.subtract(tmp2, input, tmp2)
numpy.subtract(tmp2, input, tmp2)
return tmp2
def white_tophat(input, size = None, footprint = None, structure = None,
output = None, mode = "reflect", cval = 0.0, origin = 0):
"""Multi-dimensional white tophat filter.
Either a size or a footprint, or the structure must be provided. An
output array can optionally be provided. The origin parameter
controls the placement of the filter. The mode parameter
determines how the array borders are handled, where cval is the
value when mode is equal to 'constant'.
"""
tmp = grey_erosion(input, size, footprint, structure, None, mode,
cval, origin)
if isinstance(output, numpy.ndarray):
grey_dilation(tmp, size, footprint, structure, output, mode, cval,
origin)
del tmp
return numpy.subtract(input, output, output)
else:
tmp = grey_dilation(tmp, size, footprint, structure, None, mode,
cval, origin)
return input - tmp
def black_tophat(input, size = None, footprint = None,
structure = None, output = None, mode = "reflect",
cval = 0.0, origin = 0):
"""
Multi-dimensional black tophat filter.
Either a size or a footprint, or the structure must be provided. An
output array can optionally be provided. The origin parameter
controls the placement of the filter. The mode parameter
determines how the array borders are handled, where cval is the
value when mode is equal to 'constant'.
See also
--------
grey_opening, grey_closing
References
----------
.. [1] http://cmm.ensmp.fr/Micromorph/course/sld011.htm, and following slides
.. [2] http://en.wikipedia.org/wiki/Top-hat_transform
"""
tmp = grey_dilation(input, size, footprint, structure, None, mode,
cval, origin)
if isinstance(output, numpy.ndarray):
grey_erosion(tmp, size, footprint, structure, output, mode, cval,
origin)
del tmp
return numpy.subtract(output, input, output)
else:
tmp = grey_erosion(tmp, size, footprint, structure, None, mode,
cval, origin)
return tmp - input
def distance_transform_bf(input, metric = "euclidean", sampling = None,
return_distances = True, return_indices = False,
distances = None, indices = None):
"""Distance transform function by a brute force algorithm.
This function calculates the distance transform of the input, by
replacing each background element (zero values), with its
shortest distance to the foreground (any element non-zero). Three
types of distance metric are supported: 'euclidean', 'taxicab'
and 'chessboard'.
In addition to the distance transform, the feature transform can
be calculated. In this case the index of the closest background
element is returned along the first axis of the result.
The return_distances, and return_indices flags can be used to
indicate if the distance transform, the feature transform, or both
must be returned.
Optionally the sampling along each axis can be given by the
sampling parameter which should be a sequence of length equal to
the input rank, or a single number in which the sampling is assumed
to be equal along all axes. This parameter is only used in the
case of the euclidean distance transform.
This function employs a slow brute force algorithm, see also the
function distance_transform_cdt for more efficient taxicab and
chessboard algorithms.
the distances and indices arguments can be used to give optional
output arrays that must be of the correct size and type (float64
and int32).
"""
if (not return_distances) and (not return_indices):
msg = 'at least one of distances/indices must be specified'
raise RuntimeError, msg
tmp1 = numpy.asarray(input) != 0
struct = generate_binary_structure(tmp1.ndim, tmp1.ndim)
tmp2 = binary_dilation(tmp1, struct)
tmp2 = numpy.logical_xor(tmp1, tmp2)
tmp1 = tmp1.astype(numpy.int8) - tmp2.astype(numpy.int8)
del tmp2
metric = metric.lower()
if metric == 'euclidean':
metric = 1
elif metric in ['taxicab', 'cityblock', 'manhattan']:
metric = 2
elif metric == 'chessboard':
metric = 3
else:
raise RuntimeError, 'distance metric not supported'
if sampling is not None:
sampling = _ni_support._normalize_sequence(sampling, tmp1.ndim)
sampling = numpy.asarray(sampling, dtype = numpy.float64)
if not sampling.flags.contiguous:
sampling = sampling.copy()
if return_indices:
ft = numpy.zeros(tmp1.shape, dtype = numpy.int32)
else:
ft = None
if return_distances:
if distances is None:
if metric == 1:
dt = numpy.zeros(tmp1.shape, dtype = numpy.float64)
else:
dt = numpy.zeros(tmp1.shape, dtype = numpy.uint32)
else:
if distances.shape != tmp1.shape:
raise RuntimeError, 'distances array has wrong shape'
if metric == 1:
if distances.dtype.type != numpy.float64:
raise RuntimeError, 'distances array must be float64'
else:
if distances.dtype.type != numpy.uint32:
raise RuntimeError, 'distances array must be uint32'
dt = distances
else:
dt = None
_nd_image.distance_transform_bf(tmp1, metric, sampling, dt, ft)
if return_indices:
if isinstance(indices, numpy.ndarray):
if indices.dtype.type != numpy.int32:
raise RuntimeError, 'indices must of int32 type'
if indices.shape != (tmp1.ndim,) + tmp1.shape:
raise RuntimeError, 'indices has wrong shape'
tmp2 = indices
else:
tmp2 = numpy.indices(tmp1.shape, dtype = numpy.int32)
ft = numpy.ravel(ft)
for ii in range(tmp2.shape[0]):
rtmp = numpy.ravel(tmp2[ii, ...])[ft]
rtmp.shape = tmp1.shape
tmp2[ii, ...] = rtmp
ft = tmp2
# construct and return the result
result = []
if return_distances and not isinstance(distances, numpy.ndarray):
result.append(dt)
if return_indices and not isinstance(indices, numpy.ndarray):
result.append(ft)
if len(result) == 2:
return tuple(result)
elif len(result) == 1:
return result[0]
else:
return None
def distance_transform_cdt(input, metric = 'chessboard',
return_distances = True, return_indices = False,
distances = None, indices = None):
"""Distance transform for chamfer type of transforms.
The metric determines the type of chamfering that is done. If
the metric is equal to 'taxicab' a structure is generated
using generate_binary_structure with a squared distance equal to
1. If the metric is equal to 'chessboard', a metric is
generated using generate_binary_structure with a squared distance
equal to the rank of the array. These choices correspond to the
common interpretations of the taxicab and the chessboard
distance metrics in two dimensions.
In addition to the distance transform, the feature transform can
be calculated. In this case the index of the closest background
element is returned along the first axis of the result.
The return_distances, and return_indices flags can be used to
indicate if the distance transform, the feature transform, or both
must be returned.
The distances and indices arguments can be used to give optional
output arrays that must be of the correct size and type (both int32).
"""
if (not return_distances) and (not return_indices):
msg = 'at least one of distances/indices must be specified'
raise RuntimeError, msg
ft_inplace = isinstance(indices, numpy.ndarray)
dt_inplace = isinstance(distances, numpy.ndarray)
input = numpy.asarray(input)
if metric in ['taxicab', 'cityblock', 'manhattan']:
rank = input.ndim
metric = generate_binary_structure(rank, 1)
elif metric == 'chessboard':
rank = input.ndim
metric = generate_binary_structure(rank, rank)
else:
try:
metric = numpy.asarray(metric)
except:
raise RuntimeError, 'invalid metric provided'
for s in metric.shape:
if s != 3:
raise RuntimeError, 'metric sizes must be equal to 3'
if not metric.flags.contiguous:
metric = metric.copy()
if dt_inplace:
if distances.dtype.type != numpy.int32:
raise RuntimeError, 'distances must be of int32 type'
if distances.shape != input.shape:
raise RuntimeError, 'distances has wrong shape'
dt = distances
dt[...] = numpy.where(input, -1, 0).astype(numpy.int32)
else:
dt = numpy.where(input, -1, 0).astype(numpy.int32)
rank = dt.ndim
if return_indices:
sz = numpy.product(dt.shape,axis=0)
ft = numpy.arange(sz, dtype = numpy.int32)
ft.shape = dt.shape
else:
ft = None
_nd_image.distance_transform_op(metric, dt, ft)
dt = dt[tuple([slice(None, None, -1)] * rank)]
if return_indices:
ft = ft[tuple([slice(None, None, -1)] * rank)]
_nd_image.distance_transform_op(metric, dt, ft)
dt = dt[tuple([slice(None, None, -1)] * rank)]
if return_indices:
ft = ft[tuple([slice(None, None, -1)] * rank)]
ft = numpy.ravel(ft)
if ft_inplace:
if indices.dtype.type != numpy.int32:
raise RuntimeError, 'indices must of int32 type'
if indices.shape != (dt.ndim,) + dt.shape:
raise RuntimeError, 'indices has wrong shape'
tmp = indices
else:
tmp = numpy.indices(dt.shape, dtype = numpy.int32)
for ii in range(tmp.shape[0]):
rtmp = numpy.ravel(tmp[ii, ...])[ft]
rtmp.shape = dt.shape
tmp[ii, ...] = rtmp
ft = tmp
# construct and return the result
result = []
if return_distances and not dt_inplace:
result.append(dt)
if return_indices and not ft_inplace:
result.append(ft)
if len(result) == 2:
return tuple(result)
elif len(result) == 1:
return result[0]
else:
return None
def distance_transform_edt(input, sampling = None,
return_distances = True, return_indices = False,
distances = None, indices = None):
"""Exact euclidean distance transform.
In addition to the distance transform, the feature transform can
be calculated. In this case the index of the closest background
element is returned along the first axis of the result.
The return_distances, and return_indices flags can be used to
indicate if the distance transform, the feature transform, or both
must be returned.
Optionally the sampling along each axis can be given by the
sampling parameter which should be a sequence of length equal to
the input rank, or a single number in which the sampling is assumed
to be equal along all axes.
the distances and indices arguments can be used to give optional
output arrays that must be of the correct size and type (float64
and int32).
"""
if (not return_distances) and (not return_indices):
msg = 'at least one of distances/indices must be specified'
raise RuntimeError, msg
ft_inplace = isinstance(indices, numpy.ndarray)
dt_inplace = isinstance(distances, numpy.ndarray)
# calculate the feature transform
input = numpy.where(input, 1, 0).astype(numpy.int8)
if sampling is not None:
sampling = _ni_support._normalize_sequence(sampling, input.ndim)
sampling = numpy.asarray(sampling, dtype = numpy.float64)
if not sampling.flags.contiguous:
sampling = sampling.copy()
if ft_inplace:
ft = indices
if ft.shape != (input.ndim,) + input.shape:
raise RuntimeError, 'indices has wrong shape'
if ft.dtype.type != numpy.int32:
raise RuntimeError, 'indices must be of int32 type'
else:
ft = numpy.zeros((input.ndim,) + input.shape,
dtype = numpy.int32)
_nd_image.euclidean_feature_transform(input, sampling, ft)
# if requested, calculate the distance transform
if return_distances:
dt = ft - numpy.indices(input.shape, dtype = ft.dtype)
dt = dt.astype(numpy.float64)
if sampling is not None:
for ii in range(len(sampling)):
dt[ii, ...] *= sampling[ii]
numpy.multiply(dt, dt, dt)
if dt_inplace:
dt = numpy.add.reduce(dt, axis = 0)
if distances.shape != dt.shape:
raise RuntimeError, 'indices has wrong shape'
if distances.dtype.type != numpy.float64:
raise RuntimeError, 'indices must be of float64 type'
numpy.sqrt(dt, distances)
del dt
else:
dt = numpy.add.reduce(dt, axis = 0)
dt = numpy.sqrt(dt)
# construct and return the result
result = []
if return_distances and not dt_inplace:
result.append(dt)
if return_indices and not ft_inplace:
result.append(ft)
if len(result) == 2:
return tuple(result)
elif len(result) == 1:
return result[0]
else:
return None
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