[SciPy-user] PIL and gaussian_filter?

Stéfan van der Walt stefan@sun.ac...
Wed May 21 16:42:00 CDT 2008


2008/5/21 Anne Archibald <peridot.faceted@gmail.com>:
> 2008/5/21 Stéfan van der Walt <stefan@sun.ac.za>:
>
>> 2008/5/21 Johannes Strömberg <johannes.stromberg@gmail.com>:
>>> Thanks a lot, it works like a charm.
>>>
>>> Does anyone know of an efficient way of implementing a threshold
>>> filter, i.e. where the resulting value is either the difference
>>> between the current value and the threshold (if the value is above the
>>> threshold) or otherwise 0?
>>
>> Unless you have really large data-sets, you can do:
>>
>> mask = x > threshold
>> x[~mask] = 0
>> x[mask] -= threshold
>
> Or if you want it inplace:
> np.subtract(x,threshold,x)
> np.maximum(x,0,x)

That's a good idea.  It is faster than `where`, too.

Regards
Stéfan


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