Sobel / Prewitt Edge Detection

[Chris Colbert]

Goodluck making something faster than ndimage without considerable effort
(I've already tried in Cython and was 10x slower). I read the ndimage source
and it goes to great lengths to make optimum use of the cpu cache by
allocating line buffers etc...

What we need is to find a fast open source routine, wrap it with Cython, and
package it with the scikit. I wouldn't suggest using the one from OpenCV
unless we are desperate because it's implemented as a c++ filtering engine.
However, they are using sse2 intrinsics and it's fast! Like 10x+ faster than
ndimage.


2011/4/19 Stéfan van der Walt <stefan at sun.ac.za>

> 2011/4/19 Stéfan van der Walt <stefan at sun.ac.za>:
> > Apparently, neither of these routines like integer images as inputs
> > (should be mentioned in the docs).  Here's the output for float
> > images:
>
> To be more specific, scipy.ndimage.convolve does not upcast
> appropriately when convolving integer arrays with floating point
> arrays.  This alone seems like a good enough reason to have our own
> version, although I agree that we should use the 1D separated filters.
>
> It doesn't look as if there is an easy way to coerce numpy.convolve to
> do the job, so I guess I should write something in Cython?
>
> Regards
> Stéfan
>
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