How to Merge arrays generated from the for loop-CodePudding

for a example: I have array a

 import numpy as np
 import scipy.ndimage as nd
 a=np.array(   [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
              [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
              [0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0],
              [0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0],
              [0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0],
              [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
              [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
              [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]])

my current code

def border_selection(inp_array):
    s2 = nd.generate_binary_structure(rank=2,connectivity=2)
    lab, nlab = nd.label(input=inp_array,structure= s2)
    for i in range(1, nlab   1):
        region_i = lab == i
        expanded = nd.binary_dilation(region_i, iterations=1, structure=s2)

        border = np.logical_xor(region_i, expanded)
        print(border)
l=border_selection(a)

Current output:

[[False False False False False False False False False False False]


[False  True  True  True  True  True False False False False False]
 [False  True False False False  True False False False False False]
 [False  True False False False  True False False False False False]
 [False  True False False False  True False False False False False]
 [False  True  True  True  True  True False False False False False]
 [False False False False False False False False False False False]
 [False False False False False False False False False False False]]
[[False False False False False False False False False False False]
 [False False False False False False False False False False False]
 [False False False False False False False  True  True  True  True]
 [False False False False False False False  True False False  True]
 [False False False False False False False  True False False  True]
 [False False False False False False False  True  True  True  True]
 [False False False False False False False False False False False]
 [False False False False False False False False False False False]]

Required output: 1)If i return the variable border in the above function it onlx gives the value of first array, so its returns both the arrays with print function. 2)How to combine both the array like mentioned below expected ouput

[[False False False False False False False False False False False]
 [False  True  True  True  True  True False False False False False]
 [False  True False False False  True False True  True  True  True ]
 [False  True False False False  True False True  False False True]
 [False  True False False False  True False True  False False True]
 [False  True  True  True  True  True False True  True  True  True]
 [False False False False False False False False False False False]
 [False False False False False False False False False False False]]

CodePudding user response：

You could use an array to collect the True values:

def border_selection(inp_array):
    s2 = nd.generate_binary_structure(rank=2,connectivity=2)
    lab, nlab = nd.label(input=inp_array,structure= s2)

    # set up output array initialized with False
    out = np.zeros_like(inp_array, dtype=bool)

    for i in range(1, nlab   1):
        region_i = lab == i
        expanded = nd.binary_dilation(region_i, iterations=1, structure=s2)

        border = np.logical_xor(region_i, expanded)
        out |= border # append new True values to the output
    return out

print(border_selection(a))

output:

[[False False False False False False False False False False False]
 [False  True  True  True  True  True False False False False False]
 [False  True False False False  True False  True  True  True  True]
 [False  True False False False  True False  True False False  True]
 [False  True False False False  True False  True False False  True]
 [False  True  True  True  True  True False  True  True  True  True]
 [False False False False False False False False False False False]
 [False False False False False False False False False False False]]