Thread: [Matplotlib-users] display image as (r, g, b) from a (3xMxN) nympy.array

Hi All,
i've data store in a multydimension numpy.array,
it is composed by 3 MxN normalized (0 - 1) array 
but tring to display it using "imshow" i get an error,
" TypeError: Invalid dimensions for image data "
please can you help me to fix this problem ?
my data is : 
In [119]: dd[0]
Out[119]: 
array([[[ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 ..., 
 [ 0.22834646, 0.39370079, 0.38976378, ..., 0.2519685 ,
 0.25590551, 0.38582677],
 [ 0.30708661, 0.25984252, 0.30314961, ..., 0.2480315 ,
 0.25984252, 0.37401575],
 [ 0.58661417, 0.62598425, 0.5984252 , ..., 0.2480315 ,
 0.2519685 , 0.32283465]],
 [[ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 ..., 
 [ 0.17322835, 0.37401575, 0.4015748 , ..., 0.27952756,
 0.27559055, 0.42519685],
 [ 0.30314961, 0.24409449, 0.30314961, ..., 0.26771654,
 0.27165354, 0.38976378],
 [ 0.57086614, 0.61811024, 0.5984252 , ..., 0.28346457,
 0.26771654, 0.34251969]],
 [[ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 [ 1. , 1. , 1. , ..., 1. ,
 1. , 1. ],
 ..., 
 [ 0.19685039, 0.34251969, 0.37795276, ..., 0.2519685 ,
 0.25984252, 0.34251969],
 [ 0.27165354, 0.21653543, 0.27559055, ..., 0.2519685 ,
 0.26377953, 0.30708661],
 [ 0.57480315, 0.63385827, 0.58661417, ..., 0.26377953,
 0.25590551, 0.29527559]]])
In [120]: len(dd[0])
Out[120]: 3
In [121]: dd[0].shape
Out[121]: (3, 2058, 2607)
In [122]: matplotlib.pyplot.imshow(dd[0])
------------------------------------------------------------
Traceback (most recent call last):
 File "<ipython console>", line 1, in <module>
 File "/Library/Python/2.6/site-packages/matplotlib/pyplot.py", line 2035, in imshow
 ret = ax.imshow(X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, **kwargs)
 File "/Library/Python/2.6/site-packages/matplotlib/axes.py", line 6272, in imshow
 im.set_data(X)
 File "/Library/Python/2.6/site-packages/matplotlib/image.py", line 372, in set_data
 raise TypeError("Invalid dimensions for image data")
TypeError: Invalid dimensions for image data
thanks for any help!!!
Massimo.

On Sat, Feb 27, 2010 at 11:04 PM, Massimo Di Stefano
<mas...@ya...> wrote:
> Hi All,
>
> i've data store in a multydimension numpy.array,
> it is composed by 3 MxN normalized (0 - 1) array
> but tring to display it using "imshow" i get an error,
> " TypeError: Invalid dimensions for image data "
> please can you help me to fix this problem ?
> my data is :
> In [120]: len(dd[0])
> Out[120]: 3
>
> In [121]: dd[0].shape
> Out[121]: (3, 2058, 2607)
>
> In [122]: matplotlib.pyplot.imshow(dd[0])
> ------------------------------------------------------------
> Traceback (most recent call last):
> File "<ipython console>", line 1, in <module>
> File "/Library/Python/2.6/site-packages/matplotlib/pyplot.py", line 2035,
> in imshow
> ret = ax.imshow(X, cmap, norm, aspect, interpolation, alpha, vmin, vmax,
> origin, extent, shape, filternorm, filterrad, imlim, resample, url,
> **kwargs)
> File "/Library/Python/2.6/site-packages/matplotlib/axes.py", line 6272, in
> imshow
> im.set_data(X)
> File "/Library/Python/2.6/site-packages/matplotlib/image.py", line 372, in
> set_data
> raise TypeError("Invalid dimensions for image data")
> TypeError: Invalid dimensions for image data
Your image data is 3xMxN, but according to the imshow docstring:
" MxNx3 -- RGB (float or uint8 array)"
So a quick way is to use the transpose do:
matplotlib.pyplot.imshow(dd[0].transpose())
However, this will rotate the image (result will have N rows and M
columns), if you're expecting it to have M rows and N columns. In that
case, you need to "roll" the axis to the end, which will end up with a
3xMxN array:
>>>dd[0].shape
(3, 2058, 2607)
>>>data2 = np.rollaxis(dd[0], 0, 3)
>>>data2.shape
(2058, 2607, 3)
plt.imshow(data2)
Ryan
-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma