[Numpy-discussion] 3 dim array unpacking

Anne Archibald aarchiba@physics.mcgill...
Mon Jul 12 13:30:43 CDT 2010


On 12 July 2010 13:24, K.-Michael Aye <kmichael.aye@gmail.com> wrote:
> Dear numpy hackers,
>
> I can't find the syntax for unpacking the 3 dimensions of a rgb array.
> so i have a MxNx3 image array 'img' and would like to do:
>
> red, green, blue = img[magical_slicing]
>
> Which slicing magic do I need to apply?

Not slicing exactly; unpacking happens along the first dimension, so
you need to reorder your axes so your array is 3xMxN. np.rollaxis is
handy for this, as it pulls the axis you specify to the front:

red, green, blue = np.rollaxis(img,2)

Anne
> Thanks for your help!
>
> BR,
> Michael
>
>
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