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stsci.ndimage
Package stsci :: Package ndimage :: Module interpolation
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Module interpolation

source code

Functions [hide private]
 
_extend_mode_to_code(mode) source code
 
spline_filter1d(input, order=3, axis=-1, output=<type 'numpy.float64'>)
Calculates a one-dimensional spline filter along the given axis.		 source code
 
spline_filter(input, order=3, output=<type 'numpy.float64'>)
Multi-dimensional spline filter.		 source code
 
geometric_transform(input, mapping, output_shape=None, output=None, order=3, mode='constant', cval=0.0, prefilter=True, extra_arguments=(), extra_keywords={})
Apply an arbritrary geometric transform.		 source code
 
map_coordinates(input, coordinates, output=None, order=3, mode='constant', cval=0.0, prefilter=True)
Map the input array to new coordinates by interpolation.		 source code
 
affine_transform(input, matrix, offset=0.0, output_shape=None, output=None, order=3, mode='constant', cval=0.0, prefilter=True)
Apply an affine transformation.		 source code
 
shift(input, shift, output=None, order=3, mode='constant', cval=0.0, prefilter=True)
Shift an array.		 source code
 
zoom(input, zoom, output=None, order=3, mode='constant', cval=0.0, prefilter=True)
Zoom an array.		 source code
 
_minmax(coor, minc, maxc) source code
 
rotate(input, angle, axes=(1, 0), reshape=True, output=None, order=3, mode='constant', cval=0.0, prefilter=True)
Rotate an array.		 source code
Variables [hide private]
  __package__ = 'stsci.ndimage'

Imports: math, numpy, _ni_support, _nd_image


Function Details [hide private]

spline_filter1d(input, order=3, axis=-1, output=<type 'numpy.float64'>)

source code  

Calculates a one-dimensional spline filter along the given axis.

The lines of the array along the given axis are filtered by a
spline filter. The order of the spline must be >= 2 and <= 5.

Parameters
----------
input : array_like
    The input array.
order : int, optional
    The order of the spline, default is 3.
axis : int, optional
    The axis along which the spline filter is applied. Default is the last
    axis.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array. Default is `numpy.float64`.

Returns
-------
return_value : ndarray or None
    The filtered input. If `output` is given as a parameter, None is
    returned.

spline_filter(input, order=3, output=<type 'numpy.float64'>)

source code  

Multi-dimensional spline filter.

For more details, see `spline_filter1d`.

See Also
--------
spline_filter1d

Notes
-----
The multi-dimensional filter is implemented as a sequence of
one-dimensional spline 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.

geometric_transform(input, mapping, output_shape=None, output=None, order=3, mode='constant', cval=0.0, prefilter=True, extra_arguments=(), extra_keywords={})

source code  

Apply an arbritrary geometric transform.

The given mapping function is used to find, for each point in the
output, the corresponding coordinates in the input. The value of the
input at those coordinates is determined by spline interpolation of
the requested order.

Parameters
----------
input : array_like
    The input array.
mapping : callable
    A callable object that accepts a tuple of length equal to the output
    array rank, and returns the corresponding input coordinates as a tuple
    of length equal to the input array rank.
output_shape : tuple of ints
    Shape tuple.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.
extra_arguments : tuple, optional
    Extra arguments passed to `mapping`.
extra_keywords : dict, optional
    Extra keywords passed to `mapping`.

Returns
-------
return_value : ndarray or None
    The filtered input. If `output` is given as a parameter, None is
    returned.

See Also
--------
map_coordinates, affine_transform, spline_filter1d

Examples
--------
>>> a = np.arange(12.).reshape((4, 3))
>>> def shift_func(output_coords):
...     return (output_coords[0] - 0.5, output_coords[1] - 0.5)
...
>>> sp.ndimage.geometric_transform(a, shift_func)
array([[ 0.   ,  0.   ,  0.   ],
       [ 0.   ,  1.362,  2.738],
       [ 0.   ,  4.812,  6.187],
       [ 0.   ,  8.263,  9.637]])

map_coordinates(input, coordinates, output=None, order=3, mode='constant', cval=0.0, prefilter=True)

source code  

Map the input array to new coordinates by interpolation.

The array of coordinates is used to find, for each point in the output,
the corresponding coordinates in the input. The value of the input at
those coordinates is determined by spline interpolation of the
requested order.

The shape of the output is derived from that of the coordinate
array by dropping the first axis. The values of the array along
the first axis are the coordinates in the input array at which the
output value is found.

Parameters
----------
input : ndarray
    The input array.
coordinates : array_like
    The coordinates at which `input` is evaluated.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.

Returns
-------
return_value : ndarray
    The result of transforming the input. The shape of the output is
    derived from that of `coordinates` by dropping the first axis.

See Also
--------
spline_filter, geometric_transform, scipy.interpolate

Examples
--------
>>> import stsci.ndimage
>>> a = np.arange(12.).reshape((4, 3))
>>> a
array([[  0.,   1.,   2.],
       [  3.,   4.,   5.],
       [  6.,   7.,   8.],
       [  9.,  10.,  11.]])
>>> sp.ndimage.map_coordinates(a, [[0.5, 2], [0.5, 1]], order=1)
[ 2.  7.]

Above, the interpolated value of a[0.5, 0.5] gives output[0], while
a[2, 1] is output[1].

>>> inds = np.array([[0.5, 2], [0.5, 4]])
>>> sp.ndimage.map_coordinates(a, inds, order=1, cval=-33.3)
array([  2. , -33.3])
>>> sp.ndimage.map_coordinates(a, inds, order=1, mode='nearest')
array([ 2.,  8.])
>>> sp.ndimage.map_coordinates(a, inds, order=1, cval=0, output=bool)
array([ True, False], dtype=bool

affine_transform(input, matrix, offset=0.0, output_shape=None, output=None, order=3, mode='constant', cval=0.0, prefilter=True)

source code  

Apply an affine transformation.

The given matrix and offset are used to find for each point in the
output the corresponding coordinates in the input by an affine
transformation. The value of the input at those coordinates is
determined by spline interpolation of the requested order. Points
outside the boundaries of the input are filled according to the given
mode.

Parameters
----------
input : ndarray
    The input array.
matrix : ndarray
    The matrix must be two-dimensional or can also be given as a
    one-dimensional sequence or array. In the latter case, it is assumed
    that the matrix is diagonal. A more efficient algorithms is then
    applied that exploits the separability of the problem.
offset : float or sequence, optional
    The offset into the array where the transform is applied. If a float,
    `offset` is the same for each axis. If a sequence, `offset` should
    contain one value for each axis.
output_shape : tuple of ints, optional
    Shape tuple.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.

Returns
-------
return_value : ndarray or None
    The transformed input. If `output` is given as a parameter, None is
    returned.

shift(input, shift, output=None, order=3, mode='constant', cval=0.0, prefilter=True)

source code  

Shift an array.

The array is shifted using spline interpolation of the requested order.
Points outside the boundaries of the input are filled according to the
given mode.

Parameters
----------
input : ndarray
    The input array.
shift : float or sequence, optional
    The shift along the axes. If a float, `shift` is the same for each
    axis. If a sequence, `shift` should contain one value for each axis.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.

Returns
-------
return_value : ndarray or None
    The shifted input. If `output` is given as a parameter, None is
    returned.

zoom(input, zoom, output=None, order=3, mode='constant', cval=0.0, prefilter=True)

source code  

Zoom an array.

The array is zoomed using spline interpolation of the requested order.

Parameters
----------
input : ndarray
    The input array.
zoom : float or sequence, optional
    The zoom factor along the axes. If a float, `zoom` is the same for each
    axis. If a sequence, `zoom` should contain one value for each axis.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.

Returns
-------
return_value : ndarray or None
    The zoomed input. If `output` is given as a parameter, None is
    returned.

rotate(input, angle, axes=(1, 0), reshape=True, output=None, order=3, mode='constant', cval=0.0, prefilter=True)

source code  

Rotate an array.

The array is rotated in the plane defined by the two axes given by the
`axes` parameter using spline interpolation of the requested order.

Parameters
----------
input : ndarray
    The input array.
angle : float
    The rotation angle in degrees.
axes : tuple of 2 ints, optional
    The two axes that define the plane of rotation. Default is the first
    two axes.
reshape : bool, optional
    If `reshape` is true, the output shape is adapted so that the input
    array is contained completely in the output. Default is True.
output : ndarray or dtype, optional
    The array in which to place the output, or the dtype of the returned
    array.
order : int, optional
    The order of the spline interpolation, default is 3.
    The order has to be in the range 0-5.
mode : str, optional
    Points outside the boundaries of the input are filled according
    to the given mode ('constant', 'nearest', 'reflect' or 'wrap').
    Default is 'constant'.
cval : scalar, optional
    Value used for points outside the boundaries of the input if
    ``mode='constant'``. Default is 0.0
prefilter : bool, optional
    The parameter prefilter determines if the input is pre-filtered with
    `spline_filter` before interpolation (necessary for spline
    interpolation of order > 1).  If False, it is assumed that the input is
    already filtered. Default is True.

Returns
-------
return_value : ndarray or None
    The rotated input. If `output` is given as a parameter, None is
    returned.

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