python访问numpy数组的相邻单元格

如何以有效的方式访问和修改2D numpy阵列的周围8个单元？ 我有一个像这样的2D numpy数组：

arr = np.random.rand(720, 1440)

对于每个网格单元，我想减少中心单元的10％，周围的8个单元（角单元更少），但仅限于周围单元值超过0.25。 我怀疑这样做的唯一方法是使用for循环但是想看看是否有更好/更快的解决方案。

arr = np.random.rand(720, 1440)

for (x, y), value in np.ndenumerate(arr):
    # Find 10% of current cell
    reduce_by = value * 0.1

    # Reduce the nearby 8 cells by 'reduce_by' but only if the cell value exceeds 0.25
    # [0] [1] [2]
    # [3] [*] [5]
    # [6] [7] [8]
    # * refers to current cell

    # cell [0]
    arr[x-1][y+1] = arr[x-1][y+1] * reduce_by if arr[x-1][y+1] > 0.25 else arr[x-1][y+1]

    # cell [1]
    arr[x][y+1] = arr[x][y+1] * reduce_by if arr[x][y+1] > 0.25 else arr[x][y+1]

    # cell [2]
    arr[x+1][y+1] = arr[x+1][y+1] * reduce_by if arr[x+1][y+1] > 0.25 else arr[x+1][y+1]

    # cell [3]
    arr[x-1][y] = arr[x-1][y] * reduce_by if arr[x-1][y] > 0.25 else arr[x-1][y]

    # cell [4] or current cell
    # do nothing

    # cell [5]
    arr[x+1][y] = arr[x+1][y] * reduce_by if arr[x+1][y] > 0.25 else arr[x+1][y]

    # cell [6]
    arr[x-1][y-1] = arr[x-1][y-1] * reduce_by if arr[x-1][y-1] > 0.25 else arr[x-1][y-1]

    # cell [7]
    arr[x][y-1] = arr[x][y-1] * reduce_by if arr[x][y-1] > 0.25 else arr[x][y-1]

    # cell [8]
    arr[x+1][y-1] = arr[x+1][y-1] * reduce_by if arr[x+1][y-1] > 0.25 else arr[x+1][y-1]


 
python
numpy
0s