[Insight-users] watershed -- Repeated with different results (history dependent?)

[Joshua Cates]

Hi,

Can you send us code (or pseudocode) that implements the loop you
describe?  It would help in understanding what the problem might be.

Thanks,

Josh.

On Mon, 19 Apr 2004, Atwood, Robert C wrote:

> 
> Hi,
> 
> If I use the watershed in a loop, to get a series of segmentations ;
> then choose one of the level values and run a single filter, I do not
> seem to obtain the same results as I did within the loop for the same
> parameters (level and threshold) (Also I get this behaviour if I do not
> change the threshold at all i.e. it is related to the level setting)
> 
> 
> I am guessing that this has something to do with the caching of the
> initial watershed regions as described in the user guide p359:
> 
> 
> "The relabeler object at the end of the
> mini-pipeline uses the hierarchy and the initial segmentation to produce
> an output image at any
> scale below the user-specified maximum. Data objects are cached in the
> mini-pipeline so that
> changing watershed depths only requires a (fast) relabeling of the basic
> segmentation."
> 
> In order to make efficient use this behaviour, I structured a loop so
> that the "level" is progressively decreased, so the first update of the
> watershed filter uses the highest value of the "level" desired.
> However,runnign the routine again with a single value chosen from among
> those tested does not result in the same output. I also tried updating
> the watershed once with the highest 'level' value, then changing the
> value to the target value.
> Any hints?
> 
> Thanks
> Robert 
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