如何串联2个np.ndarray？

Question

I use openCV to generate a contour that looks like this:

array([[[227, 762]],

       [[228, 762]],

       [[229, 763]],

       [[228, 764]],

       [[229, 765]],

       [[228, 766]],

       [[227, 766]],

       [[228, 766]],

       [[229, 765]],

       [[228, 764]],

       [[229, 763]],

       [[229, 762]]], dtype=int32)

This contour has type np.ndarray

When I check cnt.shape, I get (12,1,2), indicating that this is more complex than a simple 12 x 2 matrix.

This means that when I try:

In [104]: new = np.array([1,2])

In [105]: type(new)
Out[105]: numpy.ndarray

In [106]: X = np.vstack((ex,new))
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-106-5ceb3fcd9619> in <module>()
----> 1 X = np.vstack((ex,new))

/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/shape_base.pyc in vstack(tup)
    226
    227     """
--> 228     return _nx.concatenate([atleast_2d(_m) for _m in tup], 0)
    229
    230 def hstack(tup):

ValueError: all the input arrays must have same number of dimensions

You can see that new and ex are both of the same type and I was hoping that they both have 2 columns and thus I can stack them vertically, but alas, no.... How can I do this?

Answer 1

To convert it to 12x2, simply:

yourarray.reshape(12, 2)

That gets me:

array([[227, 762],
       [228, 762],
       [229, 763],
       [228, 764],
       [229, 765],
       [228, 766],
       [227, 766],
       [228, 766],
       [229, 765],
       [228, 764],
       [229, 763],
       [229, 762]])

I recommend a brief readthrough of numpy's array methods - there are lots of potentially useful stuff.