[Insight-users] Dynamic Threshold Filter

[Luis Ibanez]

Hi Christian,

There is certainly overlap of some functionalities between VTK and ITK,
particularly at the level of basic image processing filters.

When to use the functionalities of one toolkit or the other,
certainly depends on your specific application.


Regrading the volume rendering visualization in ParaView:

The issue that you are observing is unrelated to whether the data is
coming from ITK or from VTK.  Instead, the problem is that ImageData
can't be directly volume rendered in ParaView, you must first convert
the image data to an unstructured mesh.

You can easily do this with the "Tetrahedrilize" filter, from the Filters
menu,inside ParaView.  Then, you can go to the "Display" tab of that
output and select "Volume" as the "representation" mode (in the "Style"
frame).


    Regards,


         Luis


------------------------------------------------------------------------------------------
On Sun, Mar 7, 2010 at 5:09 AM, Christian Werner
<christian.werner at rwth-aachen.de> wrote:
>
> You may remember that I am working with Paraview and write VTK plugins that
> use ITK filters. However I found out that many of the image processing is
> also available in VTK, like this median and subtraction you mentioned. It
> seems that VTK and ITK has some intersection here. So I will stick to the
> VTK version whenever possible.
>
> I had some difficulties when using ITK filters anyway: Volume data that
> comes back from ITK cannot be displayed as volume in VTK anymore:
>
> Cannot volume render since no point (or cell) data available.
>
> Despite everything works fine, I can only view the data in slices. This is
> unfortunate since I finally managed to integrate Gaetens Analysis functions,
> especially the RGB labeling (which requires many common Gaeten-functions) as
> a plugin. With my superb ImageBox that's possible for any image data by the
> way! :) To bad the result which I import back to VTK can only be viewed in
> slices.
>
> I see that this is likely more of a VTK or Paraview issue, so don't bother.
> Actually I asked the VTK mailing list, but it seems that they do not have a
> Luis Ibanez there... I will try the Paraview mailing list now.
>
>
> Best regards.
> Christian
>
>
>
> Luis Ibanez wrote:
>>
>> Hi Christian,
>>
>> You could do:
>>
>> 1) Pass the input image through the
>>    MeanImageFilter (with your kernel size)
>>
>> 2) Subtract the outcome of (1) from the input
>>    image by using the SubtractImageFilter
>>
>> 3) Threshold the output of (2) with the standard
>>     BinaryThreshold image filter.
>>
>>
>> Of course, you could also implement this filter
>> by merging together the code of the Mean
>> subtract and threshold filters (not in a pipeline,
>> but as a single pass filter).
>>
>> If you take this last option, it will be great if you
>> share the filter with the ITK community by posting
>> the code as a paper to the Insight Journal   :-)
>>
>>      http://www.insight-journal.org
>>
>>
>>   Regards,
>>
>>
>>        Luis
>>
>>
>> -------------------------------
>> On Fri, Mar 5, 2010 at 1:24 PM, Christian Werner
>> <christian.werner at rwth-aachen.de> wrote:
>>
>>>
>>> Hello!
>>>
>>> I didn't get to find a dynamic threshold filter in ITK, is there such? It
>>> is
>>> typically used to extract pixel/voxels who's value differ about a certain
>>> threshold from the average of a neigborhood in a given distance (kernel
>>> size).
>>>
>>> In contrast to the simple BinaryThresholdImageFilter it catches elements
>>> that "stand out" from the neighborhood.
>>>
>>> Any suggestions?
>>>
>>>
>>> Best regards,
>>> Christian
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