Multispectral random walker segmentation

[Josh Warner]

I'd be happy to include your suggested changes, if it's simpler to go that 
route than have two separate pull requests.  I don't want to step on any 
toes regarding attribution, though.  

Having the 'soft' probabilities available is definitely a useful 
improvement (cleanup, fuzzy post-processing), and I'm glad you implemented 
that!  

Josh


On Monday, August 20, 2012 4:11:45 PM UTC-5, Emmanuelle Gouillart wrote:
>
> Hi Josh, 
>
> extending the random walker algorithm to multichannel images sounds like 
> a very nice idea, and I'm sure that it would be useful for other people 
> (including myself!). 
>
> In fact, I had started working on some improvements of the random walker 
> code but didn't go as far as proposing the pull request. I have a branch 
> for that on 
> https://github.com/emmanuelle/scikits.image/tree/fix_random_walker, maybe 
> you can include these changes when you contribute your changes? 
>
> Cheers, 
> Emmanuelle 
>
> On Mon, Aug 20, 2012 at 10:03:53AM -0700, Josh Warner wrote: 
> >    I have modified the existing random walker algorithm into a fully 
> >    backwards-compatible version which allows inclusion of multispectral 
> data, 
> >    e.g. RGBA channels or different (registered) image modalities. �I 
> really 
> >    liked the existing algorithm, so I just extended it rather than write 
> one 
> >    from scratch for my own purposes. �The overhead is minimal; 
> multispectral 
> >    processing is triggered if data is passed as an iterable of arrays 
> rather 
> >    than just an array. � 
> >    This amounts to combining image gradients as sqrt(sum-of-squares) and 
> >    dividing by sqrt(#channels). �For obvious reasons, the several 
> channels 
> >    must be pre-processed to have data on similar ranges by whitening or 
> a 
> >    similar method. �Not usually a problem for RGB, but in medical 
> imaging 
> >    this rears its head. 
> >    Would this be of interest to the community? �I'd be happy to 
> contribute 
> >    the changes if there is interest. 
>
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