matplotlib.pyplot.imread(or scipy.ndimage.imread) returns a NumPy array, not a PIL image.
Try instead:
In [25]: import Image
In [26]: img = Image.open(FILENAME)
In [32]: img.size
Out[32]: (250, 250)
In [27]: img = img.resize((160, 240), Image.ANTIALIAS)
In [28]: img.size
Out[28]: (160, 240)
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