Saving a Numpy array as an image

With matplotlib:

import matplotlib.image

matplotlib.image.imsave('name.png', array)

Works with matplotlib 1.3.1, I don't know about lower version. From the docstring:

Arguments:
  *fname*:
    A string containing a path to a filename, or a Python file-like object.
    If *format* is *None* and *fname* is a string, the output
    format is deduced from the extension of the filename.
  *arr*:
    An MxN (luminance), MxNx3 (RGB) or MxNx4 (RGBA) array.

An answer using PIL (just in case it's useful).

given a numpy array "A":

from PIL import Image
im = Image.fromarray(A)
im.save("your_file.jpeg")

you can replace "jpeg" with almost any format you want. More details about the formats here

This uses PIL, but maybe some might find it useful:

import scipy.misc
scipy.misc.imsave('outfile.jpg', image_array)

EDIT: The current scipy version started to normalize all images so that min(data) become black and max(data) become white. This is unwanted if the data should be exact grey levels or exact RGB channels. The solution:

import scipy.misc
scipy.misc.toimage(image_array, cmin=0.0, cmax=...).save('outfile.jpg')