如何扩展/膨胀 numpy 数组？

Question

我正在执行图像分析并以布尔值的形式生成种子array：

import numpy as np

# Example output array
a = np.array([[False, False, False], [False, True, False], [False, False, False]])

>>> a
array([[False, False, False],
       [False,  True, False],
       [False, False, False]])

由于我想对值周围的区域进行后续分析True，因此我想将其扩展（按一定数量，例如像素）。这将导致以下结果：

>>> a
array([[False, True, False],
       [True, True, True],
       [False, True, False]])

有没有任何function简单的方法可以解决我的“径向扩展”问题？

预先感谢，BBQuercus

Answer 1

为什么不简单地使用scipy.ndimage.binary_dilation？

import numpy as np
from scipy import ndimage

a = np.array([
    [False, False, False],
    [False,  True, False],
    [False, False, False],
])
b = ndimage.binary_dilation(a, [
    [False, True, False],
    [ True, True,  True],
    [False, True, False],
])

结果：

>>> a
array([[False, False, False],
       [False,  True, False],
       [False, False, False]])
>>> b
array([[False,  True, False],
       [ True,  True,  True],
       [False,  True, False]])

Answer 2

scipy.signal.convolve2d的解决方案：

import numpy as np
from scipy.signal import convolve2d


# Example input
# [[False False False False False]
#  [False False  True  True False]
#  [False False False False False]
#  [False False False False False]
#  [False False False False  True]]
in_array = np.zeros((5, 5), dtype=bool)
in_array[1,2] = True
in_array[1,3] = True
in_array[4,4] = True

# Kernel: here you should define how much the True "dilates"

kernel = np.asarray([[False, True, False],
                     [True, True, True],
                     [False, True, False]])

# Convolution happens here
# Convolution is not possible for bool values though, so we convert to int and
# back. That works because bool(N) == True if N != 0.
result = convolve2d(in_array.astype(int), kernel.astype(int), mode='same').astype(bool)
print(result)

# Result:
# [[False False  True  True False]
#  [False  True  True  True  True]
#  [False False  True  True False]
#  [False False False False  True]
#  [False False False  True  True]]