scipy tutorial - Baustatik-Info-Server

SciPy Reference Guide, Release 0.8.dev
>>> print binary_dilation(zeros(a.shape), struct, -1, a, border_value=1)
[[1 0 0 0 0]
[1 1 0 0 0]
[0 0 0 0 0]
[0 0 0 0 0]]
The binary_erosion and binary_dilation functions both have an iterations parameter which allows the
erosion or dilation to be repeated a number of times. Repeating an erosion or a dilation with a given structure n times
is equivalent to an erosion or a dilation with a structure that is n-1 times dilated with itself. A function is provided that
allows the calculation of a structure that is dilated a number of times with itself:
The iterate_structure function returns a structure by dilation of the input structure iteration - 1
times with itself. For instance:
>>> struct = generate_binary_structure(2, 1)
>>> print struct
[[0 1 0]
[1 1 1]
[0 1 0]]
>>> print iterate_structure(struct, 2)
[[0 0 1 0 0]
[0 1 1 1 0]
[1 1 1 1 1]
[0 1 1 1 0]
[0 0 1 0 0]]
If the origin of the original structure is equal to 0, then it is also equal to 0 for the iterated structure. If not,
the origin must also be adapted if the equivalent of the iterations erosions or dilations must be achieved
with the iterated structure. The adapted origin is simply obtained by multiplying with the number of
iterations. For convenience the iterate_structure also returns the adapted origin if the origin
parameter is not None:
>>> print iterate_structure(struct, 2, -1)
(array([[0, 0, 1, 0, 0],
[0, 1, 1, 1, 0],
[1, 1, 1, 1, 1],
[0, 1, 1, 1, 0],
[0, 0, 1, 0, 0]], type=Bool), [-2, -2])
Other morphology operations can be defined in terms of erosion and d dilation. Following functions provide a few of
these operations for convenience:
The binary_opening function implements binary opening of arrays of arbitrary rank with the given
structuring element. Binary opening is equivalent to a binary erosion followed by a binary dilation with
the same structuring element. The origin parameter controls the placement of the structuring element as
described in Filter functions. If no structuring element is provided, an element with connectivity equal to
one is generated using generate_binary_structure. The iterations parameter gives the number
of erosions that is performed followed by the same number of dilations.
The binary_closing function implements binary closing of arrays of arbitrary rank with the given
structuring element. Binary closing is equivalent to a binary dilation followed by a binary erosion with
the same structuring element. The origin parameter controls the placement of the structuring element as
described in Filter functions. If no structuring element is provided, an element with connectivity equal to
one is generated using generate_binary_structure. The iterations parameter gives the number
of dilations that is performed followed by the same number of erosions.
70 Chapter 1. SciPy Tutorial