使用numpy的Python数组操作

Question

I am trying to replicate the border of a array:

A=[1,2],[3,4] 

and want the result as

[1,1,1,2,2,2]
[1,1,1,2,2,2]
[1,1,1,2,2,2]
[3,3,3,4,4,4]
[3,3,3,4,4,4]
[3,3,3,4,4,4]

How do you do it in python? I am using

import numpy
(a,2,reflect') or wrap I am not getting this array

Answer 1

You can use a nested repeat method (example in IPython ):

In [1]: import numpy as np

In [2]: A = np.array([[1,2],[3,4]])

In [3]: A.repeat(3, 1).repeat(3, 0)
Out[3]: 
array([[1, 1, 1, 2, 2, 2],
       [1, 1, 1, 2, 2, 2],
       [1, 1, 1, 2, 2, 2],
       [3, 3, 3, 4, 4, 4],
       [3, 3, 3, 4, 4, 4],
       [3, 3, 3, 4, 4, 4]])

But for image manipulation you migth want to have a look at eg:

• Python Imaging Library (or the newer variant, pillow )
• Python interfaces to the ImageMagick suite

Especially ImageMagick provides a lot of image manipulation tools.

Answer 2

If you have numpy 1.7 or later, you can use np.pad , with mode='edge' :

In [8]: a
Out[8]: 
array([[1, 2],
       [3, 4]])

In [9]: np.pad(a, pad_width=2, mode='edge')
Out[9]: 
array([[1, 1, 1, 2, 2, 2],
       [1, 1, 1, 2, 2, 2],
       [1, 1, 1, 2, 2, 2],
       [3, 3, 3, 4, 4, 4],
       [3, 3, 3, 4, 4, 4],
       [3, 3, 3, 4, 4, 4]])