[Insight-developers] two-input filters don't work

[Kevin H. Hobbs]

On Thu, 2009-08-27 at 12:55 +0200, Michael Xanadu wrote:
> Hi folks,
> 
> I've got a problem with all segmentation filters which have two inputs
> (normal input & feature image), for example ShapeDetectionLevelSet or
> GeodesicActiveContour. I tryed the accordant examples in the example
> folders and they work great (with image files). But if I replace the
> input by a dicomreader (of course, I changed all accordant parameters,
> too) I always get a black output with a little white spot at the
> coordinate where I placed the seedpoint. I messed around with the
> filter parameters, but I never get a segment, only the spot. Is
> somebody familiar with the problem?
> 
> Michael
> 
> P.S.: dicom data = 512 x 512 x 4, short 


My guess is that your input images are not exactly right for these
filters.

The examples given in ITK take great pains to set up the feature image
and the initial levelset "just so".

The level set filters don't ever take a "normal input". I had to learn
this the hard way (very hard way in fact I just discovered that some of
my old work had edge images the wrong way around. It's no wonder they
seemed to stop early!) by disassembling the examples into many
reader->filter->writer programs and carefully looking at the outputs.

The feature image should range from 0 to 1 with values close to one
inside and outside the object, and values close to zero at its edges.

The initial level set image should have negative values inside the
object and positive values outside the object.
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