Vous êtes un professionnel et vous avez besoin d'une formation ? Mise en oeuvre d'IHM
avec Qt et PySide6 Voir le programme détaillé

Module « scipy.ndimage »

Fonction convolve - module scipy.ndimage

Signature de la fonction convolve

def convolve(input, weights, output=None, mode='reflect', cval=0.0, origin=0, *, axes=None) 

Description

help(scipy.ndimage.convolve)

Multidimensional convolution.

The array is convolved with the given kernel.

Parameters
----------
input : array_like
    The input array.
weights : array_like
    Array of weights, same number of dimensions as input
output : array or dtype, optional
    The array in which to place the output, or the dtype of the
    returned array. By default an array of the same dtype as input
    will be created.
mode : {'reflect', 'constant', 'nearest', 'mirror', 'wrap'}, optional
    The `mode` parameter determines how the input array is extended
    beyond its boundaries. Default is 'reflect'. Behavior for each valid
    value is as follows:

    'reflect' (`d c b a | a b c d | d c b a`)
        The input is extended by reflecting about the edge of the last
        pixel. This mode is also sometimes referred to as half-sample
        symmetric.

    'constant' (`k k k k | a b c d | k k k k`)
        The input is extended by filling all values beyond the edge with
        the same constant value, defined by the `cval` parameter.

    'nearest' (`a a a a | a b c d | d d d d`)
        The input is extended by replicating the last pixel.

    'mirror' (`d c b | a b c d | c b a`)
        The input is extended by reflecting about the center of the last
        pixel. This mode is also sometimes referred to as whole-sample
        symmetric.

    'wrap' (`a b c d | a b c d | a b c d`)
        The input is extended by wrapping around to the opposite edge.

    For consistency with the interpolation functions, the following mode
    names can also be used:

    'grid-mirror'
        This is a synonym for 'reflect'.

    'grid-constant'
        This is a synonym for 'constant'.

    'grid-wrap'
        This is a synonym for 'wrap'.
cval : scalar, optional
    Value to fill past edges of input if `mode` is 'constant'. Default
    is 0.0
origin : int or sequence, optional
    Controls the placement of the filter on the input array's pixels.
    A value of 0 (the default) centers the filter over the pixel, with
    positive values shifting the filter to the right, and negative ones
    to the left. By passing a sequence of origins with length equal to
    the number of dimensions of the input array, different shifts can
    be specified along each axis.
axes : tuple of int or None, optional
    If None, `input` is filtered along all axes. Otherwise,
    `input` is filtered along the specified axes. When `axes` is
    specified, any tuples used for `mode` or `origin` must match the length
    of `axes`. The ith entry in any of these tuples corresponds to the ith
    entry in `axes`.

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+k-j} 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`) are treated as zeros.

>>> import numpy as np
>>> 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]])

Vous êtes un professionnel et vous avez besoin d'une formation ? Calcul scientifique
avec Python Voir le programme détaillé