[Pkg-exppsy-pynifti] nifti extensions bug?

[Michael Hanke]

Hi,

thanks for your report. I'll take a look at it shortly.

Cheers,

Michael


On Mon, Feb 23, 2009 at 03:04:38PM -0500, Kanterakis, Efstathios wrote:
> Dear all,
> I've been using pynifti for quite a while and it has made a big
> difference in our lab. Thanks for continuing to develop and support it.
> Recently I've been playing around with Nifti header extensions and
> discovered a potential bug.
> Seems that extensions which are N*16+8 characters (bytes) in length get
> saved with junk characters appended at the end.
> 
> To re-create the problem, I attach a simple script that creates a blank
> image, adds extensions of a variety of sizes, saves the image and then
> retrieves the extensions back.
> 
> For lengths 8 and 24, with this text as input:
> 12345678
> 123456789012345678901234
> 
> I get the following text back:
> 12345678`Z~\x17'
> 123456789012345678901234!
> 
> When I use Afni's nifti_tool to display header extensions I get:
> > nifti_tool -disp_exts -infiles bug_report.nii
> header file 'bug_report.nii', num_ext = 18
>     ext #0 : ecode = 0, esize = 16, edata = (unknown data type)
>     ext #1 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #2 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #3 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #4 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #5 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #6 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #7 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #8 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #9 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #10 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #11 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #12 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #13 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #14 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #15 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #16 : ecode = 0, esize = 32, edata = (unknown data type)
>     ext #17 : ecode = 0, esize = 48, edata = (unknown data type)
> 
> So pynifti in most cases saves the extensions correctly, as per nifti
> specifications ("esize must be a positive integral multiple of 16"
> http://nifti.nimh.nih.gov/nifti-1/documentation/nifti1fields/nifti1field
> s_pages/extension.html)
> except for the case explained above.
> 
> I attach the nifti file that was created by this script for your
> convenience.
> 
> Looking forward to the next release!
> 
> Thank you very much for your help and efforts
> Regards,
> Stathis Kanterakis
> 
> 
> 
> 
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