我如何转换 数组进入 b 下面在 Python 中指定的数组并使用 numpy 库?我正在寻找一种非常有效的方法,因为我想在其上使用此方法的实际数组非常大。我应该提到,数字可以是任何数字,数字之间没有关系。另外,我试图在下图中展示我想如何对数组进行切片。
import numpy as np
a = np.arange(1, 49).reshape(6, 8)
a = [[ 1, 2, 3, 4, 5, 6, 7, 8],
[ 9, 10, 11, 12, 13, 14, 15, 16],
[17, 18, 19, 20, 21, 22, 23, 24],
[25, 26, 27, 28, 29, 30, 31, 32],
[33, 34, 35, 36, 37, 38, 39, 40],
[41, 42, 43, 44, 45, 46, 47, 48]]
b =[[1, 2, 9, 10], [2, 3, 10, 11], [3, 4, 11, 12], [4, 5, 12, 13],
[5, 6, 13, 14], [6, 7, 14, 15], [7, 8, 15, 16], [9, 10, 17, 18],
[10, 11, 18, 19], [11, 12, 19, 20], [12, 13, 20, 21], [13, 14, 21, 22],
[14, 15, 22, 23], [15, 16, 23, 24], [17, 18, 25, 26], [18, 19, 26, 27],
[19, 20, 27, 28], [20, 21, 28, 29], [21, 22, 29, 30], [22, 23, 30, 31],
[23, 24, 31, 32], [25, 26, 33, 34], [26, 27, 34, 35], [27, 28, 35, 36],
[28, 29, 36, 37], [29, 30, 37, 38], [30, 31, 38, 39], [31, 32, 39, 40],
[33, 34, 41, 42], [34, 35, 42, 43], [35, 36, 43, 44], [36, 37, 44, 45],
[37, 38, 45, 46], [38, 39, 46, 47], [39, 40, 47, 48]]
我试图找到一种具有 reshape 和转置功能的方法,但问题是我找不到包含边界的方法。 c 显示了我对解决方案的想法。c = a.reshape(3, 2, 4, 2).transpose(0, 2, 3, 1).reshape(3*4, 2*2).
图片:https://ibb.co/QC7tkPM .
最佳答案
使用 numpy 1.20 或更高版本,您可以使用 np.lib.stride_tricks.sliding_window_view
:
import numpy as np
a = np.arange(12).reshape(3, 4)
print(a)
给出:[[ 0 1 2 3]
[ 4 5 6 7]
[ 8 9 10 11]]
以下 (2,2)
是滑动窗口的形状:windows = np.lib.stride_tricks.sliding_window_view(a, (2,2))
print(windows)
它给:[[[[ 0 1]
[ 4 5]]
[[ 1 2]
[ 5 6]]
[[ 2 3]
[ 6 7]]]
[[[ 4 5]
[ 8 9]]
[[ 5 6]
[ 9 10]]
[[ 6 7]
[10 11]]]]
在早期版本的 numpy 中,使用 np.lib.index_tricks.as_strided
可以获得类似的结果。 :w = 2 # width and height of the sliding window
r, c = a.shape
size = a.itemsize
ast = np.lib.index_tricks.as_strided
windows_ast = ast(a,
shape=(r - w + 1, c - w + 1, w, w),
strides=(c * size, size, c * size, size))
print(windows_ast)
它给:[[[[ 0 1]
[ 4 5]]
[[ 1 2]
[ 5 6]]
[[ 2 3]
[ 6 7]]]
[[[ 4 5]
[ 8 9]]
[[ 5 6]
[ 9 10]]
[[ 6 7]
[10 11]]]]
请注意 numpy documentation警告 np.lib.stride_tricks.as_strided
如果可能,应该避免,因为它的结果可能会导致几个问题。如果输入数组没有连续的内存布局,上面的代码也可能会失败。在任何情况下,您都可以将结果 reshape 为所需的形状:
windows.reshape(-1, 4)
它给:array([[ 0, 1, 4, 5],
[ 1, 2, 5, 6],
[ 2, 3, 6, 7],
[ 4, 5, 8, 9],
[ 5, 6, 9, 10],
[ 6, 7, 10, 11]])
关于python - 如何将 numpy 数组拆分为重叠的图 block ?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/68878673/