[MINC-development] weird minc 2 bug

[Robert VINCENT]

Hi Jonathan,

Interesting point. Because the 'mincinfo -dimnames' option does not query
the image variable dimensions, it looks as though the dimension order was
never intended to be correct. The reported dimensions simply reflect the
_file_ order, which as you know, is independent of the variable ordering.
It just happens to be the case that most netCDF files created with our
tools will coincidentally have the same dimension ordering in the file as
in the image variable. But nothing prevents someone from creating a valid
netCDF MINC file with fewer image dimensions than file dimensions, or with
a different ordering in the image variable, and the 'mincinfo -dimnames'
option will not reflect these facts.

So I'd argue it was mistaken to use the -dimnames option assuming
that it will return only the image variables dimensions, in the proper
order. This contradicts both the code and the documented function of the
option.

However, we may have to find a way to preserve this behavior to prevent
breaking the existing perl libraries. But we should probably fix the perl
library was well, as it has probably caused some subtle bugs from time to
time.

	-bert

On Wed, 7 Jun 2006, Jonathan HARLAP wrote:

> Here's a neat one:
>
> Take a CDF file, run it through mincconvert -2 to get the corresponding
> HDF file.  Now open both file in register (or just use
> mincinfo/mincheader).  You'll see that the dimension order is, as it
> should be, identical.
>
> Now, the fun part.  Run mincinfo -dimnames on the two files, and observe
> the different dimension order.
>
> This fun bug is great in that it's a subtle little glitch in mincinfo,
> but affects many little programs, such as mni-perllib's
> MNI::MincUtilities::get_dimension_order()
>
> Example output below.
>
> Cheers,
> J
>
>
> % mincinfo  m?.mnc
> file: m1.mnc
> image: signed__ short 0 to 4095
> image dimensions: xspace zspace yspace
>      dimension name         length         step        start
>      --------------         ------         ----        -----
>      xspace                    124          1.4        -86.8
>      zspace                    256     -1.01562      118.492
>      yspace                    256     -1.01562      130.992
>
>
> file: m2.mnc
> image: signed__ short 0 to 4095
> image dimensions: xspace zspace yspace
>      dimension name         length         step        start
>      --------------         ------         ----        -----
>      xspace                    124          1.4        -86.8
>      zspace                    256     -1.01562      118.492
>      yspace                    256     -1.01562      130.992
>
>
> % mincinfo -dimnames m?.mnc
> xspace zspace yspace
>
>
> xspace yspace zspace
>
>
>
> _______________________________________________
> MINC-development mailing list
> MINC-development at bic.mni.mcgill.ca
> http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-development
>