[vtkusers] VtkConnectivity filter

[David Gobbi]

I've never used any ITK connectivity filters, but you could look at
itkConnectedComponentImageFilter and itkHardConnectedComponentImageFilter

 - David

On Tue, Mar 12, 2013 at 6:14 AM, Richard Frank <rickfrank at me.com> wrote:
> Thanks David,
>
> Yes, I looked at the threshold connectivity filter and noticed the required seeds.
>
> I have some 2d connected components/union find code that I will try to reimplement  for 3d.
>
> I just wanted to see if the connectivity filter would do what I want, and it does seem to....
>
> Do you happen to know if ITK has a general cc region find in n dimensions? We may want to link our app at some point to make use of ITK ( in spite of the different image layouts).
>
> I think your class would be a good contribution VTK- it's a basic tool that seems to be missing....
>
> Thanks
>
> Rick Frank
>
> On Mar 12, 2013, at 7:57 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>
>> Hi Richard,
>>
>> If your data is a volume, then vtkImageThresholdConnectivity might be
>> more suitable.  It requires you to set seeds, though, and I'm not sure
>> if that's what you want.
>>
>> I also have a filter in my personal collection that selects image
>> regions based on size (rather than requiring you to set seed
>> locations) and I could potentially contribute it to VTK.  Internally
>> it computes labels for each region, up to a max of 254, and the code
>> could be modified so that it outputs the labels.
>>
>> - David
>>
>> On Tue, Mar 12, 2013 at 5:43 AM, Richard Frank <rickfrank at me.com> wrote:
>>>
>>> I'm having trouble understanding the usages of the connectivity filter.
>>>
>>> I'm trying to use this filter to find and filter out regions in a volume, as one might do with bwlabeln() in matlab....
>>>
>>> What does AddRegion() do? Does that usage imply that I already know how many regions there are? Why/when would I use DeleteRegion()?
>>>
>>>
>>> If I ask for all regions, I get the whole volume even if I set a tight scalar threshold. If I ask for the largest region, I get what I would expect,  but that's not what I need.
>>>
>>> If I set specific regions, and add 0,1,2 and use a threshold that I know should work, I get nothing.
>>>
>>> So, I guess I don't understand the correct use.
>>>
>>> Any advice welcome.....
>>>
>>>
>>> Thanks
>>> Rick Frank