[vtkusers] Is it possible to clean noise in VTK?

[Iryna Pavlyshak]

>> Hello Oleksandr,
> 
> I can't imaging how Gauss helped you to remove undesirable points and
> islands? Didn't you lose important points during doing that as well?
> 
> 
> I like the second approach, using vtkImageIslandRemoval2D.
> 
> When i look at my image from front/top view, i can't see that "noise
> points" which are situated in front of the model, but when i look from
> right or left view i clearly see the "air noise points" which have to be
> removed. So using  vtkImageIslandRemoval2D is a good idea. But...the rub is
> in converting 3D image to 2D, and then back.
> 
> To my mind i see the following steps: 1)Converting 3D to 2D form certain
> field of view (right view for example). 2) Cleaning islands with
> vtkImageIslandRemoval2D 3)Converting back to 3D 4)Converting  3D to 2D form
> another field of view (here the number of views depend on the image, it
> may be enough to view form left and right, and for some images it had be
> done more transformation) 5)cleaning islands with vtkImageIslandRemoval2D 
> 6)Converting back to 3D and so on.. You mentioned about converting
> function. Could you send them to me?
> 
> 
> Another conclusion is to write your own filter analogous to
> vtkImageIslandRemoval2D but which would work with 3D points. I am working
> on it right now but... regarding 3D points set there are so many
> conditions, so i don't know when it will be workable.
> 
> Also if you look in previous replies to my email, you will see the advice
> about "clipping". Right now i don't know how to use it, as i have
> difficulties in setting parameters for implicit function.
> 
> best,
> 
> Iryna
> 
> 
> 
> 
> 
> 
> 
> 
> Dear Iryna,
>> 
>> For such task I used vtkImageGaussianSmooth in the following way: I 
>> smoothed 2D images, and then collect them in 3D array. Of course it is 
>> not very good, but it works. Morover almost all data is originated from
>>  2D (native 3D measuring is very complicated), so you can process your 
>> data before putting it to 3D. I had similar task, so I made 2 functions
>>  for converting array to ImageData and back, and use GausianSmooth with
>>  method: gausIm->SetStandardDeviation(SmoothPoints). Actually there is 
>> another filter: vtkImageIslandRemoval2D, but it works strange. In VTK 
>> Textbook there is similar example, and HighPass filter is used (again
>> on 2D data), but it is very slow. Unfortunatelly I didn't find any
>> native 3D filter to remove islands - I suppose it is not hard to do
>> after isoconturing, but there is no such filter in VTK, as far as I
>> know. If you want more detailed instruction how to implement 
>> vtkImageGaussianSmooth - I will send you. If you find something better
>> - please let me know.
>> 
>> Oleksandr.
>> 
>> 
>> 
>>> Gaussian filter is really very good,but not in my case, as it reduces
>>>  noise in 2D signals, so it works with pixels. I process 3D image.
>>> But there is no even any voxels. My data is a set of points every
>>> point has x, y, z coordinates), so it is 3d array. These points form
>>> the surface of the image. But some of them are undesirable, which come
>>> from air for example, them i want to delete. Iryna
>> 
>>> i think u can use vtkImageGaussianSmooth, i have tried it with my 2D 
>>> images and it works..(smoothing process can reduce noise in the image
>>>  but blur the image also)
>>> 
>>> hope it helps..=p
>>> 
>>> 
>>> Quoting Pierre Barbier de Reuille :
>>> 
>>>> What do you mean by "cleaning" your data? Even though there is 
>>>> probably a way to do it, you have to be more precise about what you
>>>>  want to do !
>>>> 
>>>> Pierre
>>>> 
>>>> On 10/23/07, Iryna Pavlyshak  wrote:
>>>>> 
>>>>> Hello!!
>>>>> 
>>>>> My point clouds have to many additional points. Up to now i used 
>>>>> commercial software and cleaned manually my data before
>>>>> processing in VTK. Can i use VTK to do this. If somebody have
>>>>> already faced with the same problem, please let me know if exist
>>>>> any solution in VTK.
>>>>> 
>>>>> Any advice will be helpful,
>>>>> 
>>>>> Iryna
>>>>> 
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>>>>> 
>>>>> 
>>>> 
>>>> 
>>>> -- Barbier de Reuille Pierre
>>>> 
>> 
>