[Insight-users] filter applied to every 10th column of image

[john]

hi,

I'm having a question about how to best apply a mean filter to every 10th column
of a image.
Since the image is quite big and the programm should be as fast as possible, I
would like to apply a mean filter to every 10th column first.
Then I could reduce the size of the image and apply a mean filter to the reduced
image.

Now my question is how to realize such a filter only applied to a specific
regions in the image. What would be the best and fastest version to do this.

Thanks in advance for your help.
john