[Insight-users] WatershedImageFilter row misalignment problem (bug?)

[Joshua Cates]

Hi Jarek,

Yes this could very well be a bug in the way the input regions are
handled.  I'll have a look at this.  Should be easy to correct.

Josh.

______________________________
 Josh Cates
 School of Computer Science
 University of Utah
 Email: cates@sci.utah.edu
 Phone: (801) 587-7697
 URL:   www.cs.utk.edu/~cates


On Mon, 20 May 2002, Jarek Sacha wrote:

>
> WatershedImageFilter row misalignment problem (bug?)
>
> I was trying to create a very simple program that loads a 2D image
> from a file, runs it through a watershed filter, and saves output
> (basic segmentation) to a file. The code is something like this:
>
>   typedef WatershedImageFilter<InputImageType> WatershedFilterType;
>   typedef WatershedFilterType::Pointer WatershedFilterPointer;
>
>   InputImagePointer inputImage = readImagePNG(inputFileName);
>
>   WatershedFilterPointer filter = WatershedFilterType::New();
>   filter->SetThreshold(0);
>   filter->SetLevel(1);
>   filter->SetInput(inputImage);
>
>   OutputImagePointer ouputImage = filter->GetBasicSegmentation();
>
>   filter->Update();
>   writeImageRaw(ouputImage, outputFileName);
>
> The problem is that the output image has missaligned raws. Each row is
> shifted by one pixel to the right in relation to previous row. This is
> probably due to assumption made in WatersheadSegmenter::GenerateData()
> method about one pixel padding. However, the WatershedImageFilter
> documentation does not mention anything about requiring padding in the
> input image.
>
> Not counting the missalignmentm, the segmentation seems to be correct.
> Is this a bug in the WatershedImageFilter? Am I setting the
> WatershedImageFilter correctly?
>
> Thanks,
>
> Jarek
>
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