extend_slice#

extend_slice(slices, shape, pad=1)[source]#

Adjust slice indices to include additional voxles around the slice.

This function does bounds checking to ensure the indices don’t extend outside the image.

Parameters:

  • slices (list of slice objects) – A list (or tuple) of N slice objects, where N is the number of dimensions in the image.

  • shape (array_like) – The shape of the image into which the slice objects apply. This is used to check the bounds to prevent indexing beyond the image.

  • pad (int or list of ints) – The number of voxels to expand in each direction.

Returns:

slices – A list slice of objects with the start and stop attributes respectively incremented and decremented by 1, without extending beyond the image boundaries.

Return type:

list of slice objects

Examples

>>> from scipy.ndimage import label, find_objects
>>> from porespy.tools import extend_slice
>>> im = np.array([[1, 0, 0], [1, 0, 0], [0, 0, 1]])
>>> labels = label(im)[0]
>>> s = find_objects(labels)

Using the slices returned by find_objects, set the first label to 3

>>> labels[s[0]] = 3
>>> print(labels)
[[3 0 0]
 [3 0 0]
 [0 0 2]]

Next extend the slice, and use it to set the values to 4

>>> s_ext = extend_slice(s[0], shape=im.shape, pad=1)
>>> labels[s_ext] = 4
>>> print(labels)
[[4 4 0]
 [4 4 0]
 [4 4 2]]

As can be seen by the location of the 4s, the slice was extended by 1, and also handled the extension beyond the boundary correctly.

Examples

Click here to view online example.