[Neuroimaging] compute_mask - algorithm changed?
Matthew Brett
matthew.brett at gmail.com
Tue Sep 29 02:18:51 CEST 2015
On Mon, Sep 28, 2015 at 5:13 PM, Matthew Brett <matthew.brett at gmail.com> wrote:
> Hi guys,
>
> One of our post-docs here was just asking about `nipy.labs.compute_mask`.
>
> The docstring for that function has:
>
> Compute and write the mask of an image based on the grey level
> This is based on an heuristic proposed by T.Nichols:
> find the least dense point of the histogram, between fractions
> m and M of the total image histogram.
>
> but I think the actual algorithm is:
>
> * Sort values;
> * Remove m from start and M from end of the sorted vector;
> * Find the value to value difference;
> * Use the value corresponding to the position of the largest
> difference as a threshold.
>
> Is that right? Did the algorithm change at some point?
Ah - sorry - with a moment's reflection, I see that the large
difference between the sorted values also represents a local point of
low histogram density...
Cheers2,
Matthew
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