Allow mmap to be used in Read Only mode about nibabel

[matthew-brett]

Are you sure that you can change the file using the current nibabel? The default mmap mode is 'c' - so - as I understand it - the OS will make a new memory copy when the array is changed, and will not change the file on disk.

In [1]: import nibabel as nib
In [4]: import numpy as np
In [5]: img = nib.Nifti1Image(np.zeros((2,3,4)), np.eye(4))
In [6]: nib.save(img, 'test.nii')
In [7]: img2 = nib.load('test.nii')
In [9]: data = img2.get_data()
In [10]: type(data)
Out[10]: numpy.core.memmap.memmap
In [11]: data[0] = 99
In [13]: del(img2)
In [14]: del(data)
In [15]: img3 = nib.load('test.nii')
In [16]: img3.get_data()
Out[16]: 
memmap([[[ 0.,  0.,  0.,  0.],
        [ 0.,  0.,  0.,  0.],
        [ 0.,  0.,  0.,  0.]],

       [[ 0.,  0.,  0.,  0.],
        [ 0.,  0.,  0.,  0.],
        [ 0.,  0.,  0.,  0.]]])

[chrisgorgo]

My bad - I must have misunderstood the discussion going on the mailing list. I did not realise that nibabel always opens files with mode='c' instead of using the default value (which is 'r+'). It is all good then.