AW: [Insight-users] Fill Black Spot

[Luis Ibanez]

Hi Helder,

In addition to Zein's excellent suggestion,
you could also consider the following options:


1) Preprocess the image with one of the
    anisotropic diffusion filters:

    - CurvatureFlow
    - CurvatureAnisotropicDiffusion
    - GradientAnisotropicDiffusion

    These filters will reduce the noise
    level in the image, which may be
    preventing your thresholding from
    capturing all the pixels on the
    region.  You will have to play
    a bit with the parameters of these
    filters.

    They are described in the software guide
    http://www . itk . org/ItkSoftwareGuide . pdf
    on section 5.5.2, pdf-page 121.

    If you use the RegionGrowingSegmentation
    application in InsightApplications, you
    have the option of pre-processing with any
    of the three filters, and then run the
    ConnectedThreshold filter.

2) Whether you do (1) or not, you could
    fill up small holes in the output image
    by applying Mathematical Morphology, for
    example doing dilation followed by erosion.
    You may want to use a structuring element
    with a size similar to the holes you want
    to fill.

    Dilation/Erosion binary filters are
    described in the SoftwareGuide on section
    5.4.3, pdf-page 111.


3) A set of filters were recently added to
    the toolkit, They are explicity designed
    for 'hole filling'. You may have to use
    an updated CVS checkout in order to get
    these filters.
 
http://www . itk . org/Insight/Doxygen/html/classitk_1_1GrayscaleFillholeImageFilter . html
http://www . itk . org/Insight/Doxygen/html/classitk_1_1GrayscaleGeodesicDilateImageFilter . html
http://www . itk . org/Insight/Doxygen/html/classitk_1_1GrayscaleGeodesicErodeImageFilter . html

    This may be an overkill since the filters
    are intended to be used in grayscale images.
    But still is an interesting option to try
    in case (1) and (2) prove to be insufficient.



Regards,


    Luis


-----------------------------

salah wrote:
> If I have understood you well, these "white spots" 
> are holes inside the segmented region that need  to 
> be filled. If this is the case, I would suggest you:
> 
> 1. do some sort of flood filling starting from some point
> outside your segmented region (some external black 
> point)
> 2. invert the image generated by the flood filling. You
> will then get your original segemented region with all 
> (internal) holes filled.
> 
> Regards,
> Zein
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: Helder Carvalho [mailto:hel_carvalho at hotmail . com]
> Gesendet: Montag, 16. Juni 2003 11:47
> An: insight-users at public . kitware . com
> Betreff: [Insight-users] Fill Black Spot
> 
> 
> Hi users,
> 
> I'm using the ConnectedThresholdImageFilter to segment an image. The problem 
> is i can't get a clear output image. It still gets some black spots where 
> there should be a clear white image. So what i want to do is to directly 
> change the image pixel of the segmented image in order to fill the black 
> spots with white pixels. The black spot is inside a large white region. Is 
> there any image filter that can perform this white filling ???
> 
> Thanks,
> Helder Carvalho
> 
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