[Insight-developers] question regarding nifti IO

[Hans Johnson]

Nick,

The reason is that the image dimensions are stored in ³short integers²

Insight/Utilities/nifti/niftilib/nifti1.h:157

short dim[8];        /*!< Data array dimensions.*/  /* short dim[8];
*/

echo "2^15-1"|bc -l
32767

Hans


On 4/28/09 8:03 PM, "Nicholas Tustison" <ntustison at gmail.com> wrote:

> Developers,
> 
> My colleague, Brian Avants, asked that I post the following question to the
> Insight Developers' list.  Essentially, as he points out below, and I've
> reproduced using my own code, it seems as though 1-D images can't be created
> in nifti format where the size exceeds ~30,000 pixels but can be created using
> the mhd format.  Is this behavior known and is there a particular reason for
> it?
> 
> Thanks,
> Nick Tustison
> 
> Begin forwarded message:
> 
>> From: brian avants <stnava at gmail.com>
>> Date: April 28, 2009 1:48:58 PM EDT
>> To: Nicholas Tustison <ntustison at gmail.com>
>> Subject: bug nifti writer?
>> 
>>  
>> 
>>  
>> is this a known/unknown bug?
>> 
>> only appears to happen if #voxels exceeds about 30,000.
>> suggesting datatype problem.
>> 
>> see below: 
>> 
>> # first, just print the mhd header
>>  
>> $ PrintHeader zero2.mhd
>>  Spacing [1, 1]
>>  Origin [0, 0]
>>  Direction 
>> 1 0
>> 0 1
>>  Size 
>> [1, 65536]
>> 
>> # convert to nifti
>>  $ MultiplyImages 2 zero2.mhd 1 zero2.nii
>> 
>> # print nifti header
>> $ PrintHeader zero2.nii
>>  Spacing [1, 1]
>>  Origin [0, 0]
>>  Direction 
>> 1 0
>>  0 1
>> 
>>  Size 
>> [1, 1]
>> 
>> # size is wrong in terms of the header info
>> # but not in terms of the raw data ...
>> $ ls -l zero2.nii
>> -rw-r--r--  1 user  user  262496 Apr 28 13:37 zero2.nii
>>  
>> $ ls -l zero2.raw
>> -rw-r--r--  1 user  user  262144 Mar 25  2008 zero2.raw
>> 
>> # if i convert zero2.nii to mhd the size is wrong
>> ls -l zero3.raw 
>> -rw-r--r--  1   user  user  4 Apr 28 13:42 zero3.raw
>>  
>> 
>> 
> 
> 
> 
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