[MINC-users] mincblur and single slices

[Alex Zijdenbos]

I ran into a number of mincblur oddities when dealing with
single-slice minc volumes. For example, I have a single-slice image
that, when blurred with:

   mincblur -no_apodize -dim 2 -fwhm 1 <in.mnc> <out>

generates the expected result; However, when I happened to convert the
datatype of that same slice from byte to short ran the same mincblur
call, the result suffered from a wraparound effect. See the image at

   http://dl.dropbox.com/u/5709165/mincblur/test_blur.jpg

with the underlying data in

   http://dl.dropbox.com/u/5709165/mincblur/test_blur.tar.gz

I have also seen such wraparound effects appear as a function of image
dimensions (regardless of data type). So from what I can tell mincblur
is broken when it comes to dealing with single-slice data; but broken
in a somewhat unpredictable way because in certain circumstances it
will actually do the right thing (as in the 'byte' example I gave).
Padding the image with a slice above and below will make the problem
from this example go away; but again, I am not sure how the failures
depend on the number of slices added.

Is anybody familiar enough with the innards of mincblur to address
this issue? Ideally it would be fixed such as to allow proper 2D
blurring on single-slice volumes; but barring that, it would be good
if at least it generated an error as opposed to silently and
unpredictably doing the right or wrong thing.

Thanks,

-- Alex