2021-01-14 08:07:24 +01:00
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from warnings import warn
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import numpy as np
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from scipy import ndimage as ndi
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from .rank import generic
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def median(image, selem=None, out=None, mode='nearest', cval=0.0,
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behavior='ndimage'):
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"""Return local median of an image.
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Parameters
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----------
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image : array-like
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Input image.
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selem : ndarray, optional
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If ``behavior=='rank'``, ``selem`` is a 2-D array of 1's and 0's.
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If ``behavior=='ndimage'``, ``selem`` is a N-D array of 1's and 0's
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with the same number of dimension than ``image``.
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If None, ``selem`` will be a N-D array with 3 elements for each
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dimension (e.g., vector, square, cube, etc.)
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out : ndarray, (same dtype as image), optional
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If None, a new array is allocated.
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mode : {'reflect', 'constant', 'nearest', 'mirror','‘wrap'}, optional
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The mode parameter determines how the array borders are handled, where
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``cval`` is the value when mode is equal to 'constant'.
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Default is 'nearest'.
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.. versionadded:: 0.15
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``mode`` is used when ``behavior='ndimage'``.
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cval : scalar, optional
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Value to fill past edges of input if mode is 'constant'. Default is 0.0
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.. versionadded:: 0.15
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``cval`` was added in 0.15 is used when ``behavior='ndimage'``.
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behavior : {'ndimage', 'rank'}, optional
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Either to use the old behavior (i.e., < 0.15) or the new behavior.
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The old behavior will call the :func:`skimage.filters.rank.median`.
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The new behavior will call the :func:`scipy.ndimage.median_filter`.
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Default is 'ndimage'.
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.. versionadded:: 0.15
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``behavior`` is introduced in 0.15
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.. versionchanged:: 0.16
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Default ``behavior`` has been changed from 'rank' to 'ndimage'
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Returns
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-------
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out : 2-D array (same dtype as input image)
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Output image.
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See also
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--------
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skimage.filters.rank.median : Rank-based implementation of the median
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filtering offering more flexibility with additional parameters but
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dedicated for unsigned integer images.
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Examples
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--------
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>>> from skimage import data
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>>> from skimage.morphology import disk
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>>> from skimage.filters import median
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>>> img = data.camera()
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>>> med = median(img, disk(5))
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"""
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if behavior == 'rank':
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if mode != 'nearest' or not np.isclose(cval, 0.0):
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warn("Change 'behavior' to 'ndimage' if you want to use the "
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"parameters 'mode' or 'cval'. They will be discarded "
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"otherwise.")
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return generic.median(image, selem=selem, out=out)
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if selem is None:
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selem = ndi.generate_binary_structure(image.ndim, image.ndim)
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return ndi.median_filter(image, footprint=selem, output=out, mode=mode,
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cval=cval)
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