generic non-linear filtering that support selem and boundary handling

[Juan Nunez-Iglesias]

Josh, why the parallel stripping out? Is it a Cython version requirement?
We can always have this as a "dormant" PR for 1.0, for which we might bump
up the version required. It might also be possible to wrap the import
around a try-catch clause so that it fails gracefully on an earlier Cython
version.

Juan.


On Tue, May 27, 2014 at 1:07 PM, Josh Warner <silvertrumpet999 at gmail.com>wrote:

> Funny you should request this. I built a Cython framework do exactly what
> you want (arbitrary selem, boundary handling [padding], and even arbitrary
> weighting of the selem in 2D and 3D) for local *weighted *variance.
>
> The framework is about as useful as the actual calculation. Replace the
> innermost loop, change the name, and you get an entirely different
> non-linear weighted local feature. This requires a somewhat skilled user,
> but the framework is already done so it isn't as hard as it sounds.
>
> Trouble is, I used some features from cython.parallel so those would have
> to be stripped out, losing over an order of magnitude in speed. I've been
> kicking around submitting them, but going back and ripping out the parallel
> features is painful.
>
> If interested I can clean up and put them in a Gist or two.
>
> Josh
>
>
> On Monday, May 26, 2014 1:50:10 AM UTC-5, Chencan QIAN wrote:
>>
>> Essentially, this is something similar to scipy.ndimage.filters.generic_filter
>> (which is too slow because of its internal python for-loop), but
>> implemented in cython as with skimage.filter.rank family.
>>
>> Given the diversity within skimage.filter.rank, a generic function would
>> be very useful. For example, I'd like to calculate local variance, which is
>> conceptually similar to skimage.filter.rank.mean, but not supported
>> currently.
>>
>> I guess the absence of such a function must be due to some unresolved
>> technical obstacle?
>>
>> Thanks~
>>
>> Chencan
>>
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