[Insight-users] Issue with BinaryErodeImageFilter

[Robert Tamburo]

Hi all,

I'm trying to use the erosion filter on a 3D binary image. I'm using  
the itkBinaryErodeImageFilter with an itkBinaryBallStructuringElement  
in the same way that is demonstrated in the SoftwareGuide. The input  
image has a total of 19 slices with the first and last slices being  
blank (black, background). In the output image the first 2 and last 2  
slices end up being blank... two slices of data are missing.   
Moreover, an obviously corresponding slice no longer has the same index.

I tried a couple of things to try and understand what was happening.  
First, I tried padding the image with additional blank slices. I  
added 1, 2, and 3 additional slices and got the same results.  Then I  
tried removing the blank slices. No blank slices were introduced.  
However, the index problem is still an issue.  I've created a temp  
web page with some screen captures to better illustrate the problem.  
The URL is: http://www.tamburo.us/temp/erosion.htm

The results are confusing to me and not what I expected. Any  
clarification on these issues would be greatly appreciated. Source  
code and images can be made available if needed.

Regards,
Robert

P. S. I'm using a MacBook Pro with ITK version 3.2.0 and gcc 4.0.1.
P. P. S. The documentation in the header for the erosion filter is  
incorrect in that it describes dilation.