[Insight-users] Performing operations on masks

[Miller, James V (Research)]

Ivan, 

I added this MaskNeighborhoodOperatorImageFilter last week. Let me 
know if you have any issues.  I have used the filter in my own application
but have not had a chance to write a test for the filter.  There could
be some cross platform compiler issues that I have seen yet. 

The NormalizedCorrelationImageFilter also will operate with a Mask.

There is also a LabelStatisticsImageFilter that takes an intensity
image and a label map (mask with several different labels).  This 
filter will calculate the image statistics of the intensity image
pixels associated with each distinct label.

I want to add some other filters that operate under a mask.  Things like
DiscreteGaussian, Gradients, and maybe even the unary/binary/ternary/nary 
image filters.

Not that if you are performing a separable operation under a mask, each
of the separable operations may need a slightly different mask (earlier
operations may need slightly dilated masks in order to produce all the 
data that later operations may need).

Jim



-----Original Message-----
From: insight-users-bounces+millerjv=crd.ge.com at itk.org
[mailto:insight-users-bounces+millerjv=crd.ge.com at itk.org]On Behalf Of
Iván Macía
Sent: Wednesday, May 18, 2005 7:49 AM
To: 'Iván Macía'; 'Insight Users'
Subject: RE: [Insight-users] Performing operations on masks


Hi again,

Answering to myself I have found a wonderful new
itk::MaskNeighborhoodOperatorImageFilter in the CVS that is 3 days old :)
It seems like this will do the job. I will give it a try.

Cheers

Ivan Macia


-----Mensaje original-----
De: insight-users-bounces+imacia=vicomtech.es at itk.org
[mailto:insight-users-bounces+imacia=vicomtech.es at itk.org] En nombre de Iván
Macía
Enviado el: miércoles, 18 de mayo de 2005 11:20
Para: Insight Users
Asunto: [Insight-users] Performing operations on masks


Dear users,

Is there any easy way to perform operations only on certain pixels of the
image defined by a mask (i.e. the result of a segmentation) ? What I want to
do is to perform some calculations only in the pixels that are part of my
segmentation, for example calculating some statistics of the pixels and
their neighborhood etc. 

It occurs to me that the natural way of doing this in itk is taking the
original image and the masked image, use an iterator for each (mask and
image), and calculate the values using the image iterator only for the
pixels whose value are not zero in the mask iterator. I could also perform a
binary AND with the image and the mask and make the calculations on the
non-zero pixels (the problem here is when there are pixels with zero value
among the segmented pixels).

My question here is : is this the best way to do this ? Is there any
automatic way of doing this now in itk ? I guess that this would be
something similar to defining a region for processing by combining an
itk::Region and a mask the same size. 

Thanks in advance for your help

Ivan Macia


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