[Insight-users] Watershed Behavior

[Albert Huang]

Thanks Richard and Gaetan

The new filter works very well on the edges for my application. However, 
when I relabel my image after the morphological watershed, I get a wrap 
around on the very top and bottom grids (even though they are alternating 
intensity blocks). Is that a known behavior?

        http://www.ece.ubc.ca/~alberth/watershed_morph.png

The left and right image edge labels are ok with no wrap around. Checking 
the gradient magnitude image, all image edges have 0 gradient (top, bottom, 
left, right).

My morphological watershed filter has
    input (double)
    output (unsigned long)
    SetMarkWatershedLine=false.
My relabel component image filter has
    input (unsigned long)
    output (unsigned int)
The relabeler outputs for my example are [1...342] which seems to be still 
well within the range of my output type.

Albert

----- Original Message -----
From: "Gaetan Lehmann" <gaetan.lehmann at jouy.inra.fr>
To: "Albert Huang" <alberth+itk at ece.ubc.ca>
Cc: <Richard.Beare at ieee.org>; <insight-users at itk.org>
Sent: Thursday, February 08, 2007 1:48 AM
Subject: Re: [Insight-users] Watershed Behavior


Hi,

You may also want to test the morphological watershed Richard and I have
contributed, and see if it gives better results.

http://hdl.handle.net/1926/202

You can also found this new filter in ITK cvs now.

Regards,

Gaetan


On Thu, 08 Feb 2007 04:34:39 +0100, Richard Beare
<richard.beare at gmail.com> wrote:

> Have a look at the gradient image and dheck whether there are plateaus
> in the zig-zag area. The behaviour of the standard itk watershed is
> somewhat arbitary in the presence of plateaus.
>
>
> On 2/8/07, Albert Huang <alberth+itk at ece.ubc.ca> wrote:
>>
>>
>> Dear experts
>>
>> I was just playing with the watershed pipeline a few days ago using a
>> checkerboard pattern (with uint8 grids of black=64, gray=153,
>> white=192),
>> and observed a zig-zaggy pattern on some edges (see
>> http://www.ece.ubc.ca/~alberth/watershed.png). Adding a
>> smooth field on the checkboard results in more zig-zaggy behaviors on
>> edges
>> that seem fairly strong in the input image. I am wondering if this is
>> normal
>> behavior for the itkWatershedImageFilter?
>>
>> My pipeline (ITK 3.0.1) setup is as below:
>>     file reader ->
>>     vector gradient magnitude image filter (pca off) ->
>>     watershed (level=0.2, threshold=0.0) ->
>>     relabel component
>>
>> p.s. The black regions in the outputs are colormap problems and not a
>> watershed issue. =)
>>
>> Thanks
>> Albert
>>
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>>
>>
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-- 
Gaëtan Lehmann
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
http://voxel.jouy.inra.fr