`scipy.ndimage._morphology:grey_erosion`

source: /scipy/ndimage/_morphology.py :1174

Signature

   def     grey_erosion (    input    ,    size    =  None   ,    footprint    =  None   ,    structure    =  None   ,    output    =  None   ,    mode    =  reflect   ,    cval    =  0.0   ,    origin    =  0   ,  * ,     axes    =  None     )

Summary

Calculate a greyscale erosion, using either a structuring element, or a footprint corresponding to a flat structuring element.

Extended Summary

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 or structure 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. The structure array applies a subtractive offset for each pixel in the neighborhood.
output : array, optional: An array used for storing the output 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
axes : tuple of int or None: The axes over which to apply the filter. If None, input is filtered along all axes. If an origin tuple is provided, its length must match the number of axes.

Returns

output : ndarray: Grayscale erosion of input.

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].

Array API Standard Support

grey_erosion has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable SCIPY_ARRAY_API=1 and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

====================  ====================  ====================
Library               CPU                   GPU
====================  ====================  ====================
NumPy                 ✅                     n/a                 
CuPy                  n/a                   ✅                   
PyTorch               ✅                     ⛔                   
JAX                   ⚠️ no JIT             ⛔                   
Dask                  ⚠️ computes graph     n/a                 
====================  ====================  ====================

See dev-arrayapi for more information.

Examples

from scipy import ndimage
import numpy as np
a = np.zeros((7,7), dtype=int)
a[1:6, 1:6] = 3
a[4,4] = 2; a[2,3] = 1
a
ndimage.grey_erosion(a, size=(3,3))
footprint = ndimage.generate_binary_structure(2, 1)

✓

footprint

✗

ndimage.grey_erosion(a, footprint=footprint)

✓

Aliases

scipy.ndimage.grey_erosion