nifti2_data_format
nifti2_data_format > RE: NIFTI-2 proposal
Mar 15, 2011 05:03 PM | Mark Jenkinson
RE: NIFTI-2 proposal
Response to the
postings on the public forum:
The NIfTI
committee thank all those who responded to the public announcement
of the NIfTI-2 proposal. The outcomes of discussions of these
postings and other responses outside of the forum are summarised
below. Please see the associated posting for full details of
the revised, finalised NIfTI-2 format.
Changes
to the proposed NIfTI-2 format:
-
Removal of unused fields (data_type, db_name, extents,
session_error, regular, glmax, glmin).
-
Changing the order of several fields to ensure 8-byte alignment of
all doubles (an issue raised outside of the forum, which would be a
major problem on some platforms if it was not ensured).
-
Shifting the magic string to the front of the header, immediately
following sizeof_hdr.
- A
change in the total header size (including 4-byte extension info)
to become 544 bytes.
- A
range for customised codes for INTENT, XFORM, UNITS and SLICE will
be specified for temporary customisation, although users will
continue to be encouraged to register for official codes and have
them publicly documented to avoid any hidden or private information
polluting the open standard.
Additional points:
-
There was considerable discussion about the hdr/img format and
although several people were in favour of dropping this to distance
the format from the older Analyze standard, it was still being
actively used by some developers and has the potential for
considerable benefit when dealing with very large datasets, where
the header information can be read and modified without requiring
any reading or writing of the data values. Consequently, it was
felt that it was more advantageous to retain the existing hdr/img
format and also leave the extension name for the single format
(.nii) unchanged.
- The
changes in nifticlib will be considered carefully, although these
are separate issues from the definition of the NIfTI-2 standard
itself.
- The
standardisation of spatial transformation information is an
important issue and currently being looked into in a separate
endeavour on developing a standard format for spatial
transformation data.
-
There were several requests for changes in how the spatial
coordinate information is stored and represented (qform and sform)
or even suggestions that the coordinate handedness should be
forced/fixed, and multiple transformations be
incorporated. The original intention of the proposed NIfTI-2
format was to create an easy to implement upgrade of the existing
NIfTI-1 standard that maintains the same information and the same
logic. This was a very important point in getting many of the
developers to agree to implement this NIfTI-2
standard. Several developers depend on the way that the qform
and sform information is currently implemented in NIfTI-1 and
changes in meaning or even storage method could cause problems and
delays in implementing the NIfTI-2 standard. The qform and
sform issues are therefore much bigger issues than being considered
for NIfTI-2 and would alter the logic involved in any
implementation compared to NIfTI-1. Therefore, although these
issues are extremely important, we feel they are more appropriate
for the upcoming discussions on future formats where such major
changes to the logic and implementation can be made without
restriction. All comments should therefore be forwarded to the
discussion forum for future formats.
- A
request to have a pure XML header is also a major change and shares
some of the same issues as the above request, and so should be
forwarded to the discussion forum for future formats. Note
that there has never been an official nifti-1 format that allowed a
purely XML header - there is some code in nifticlib to allow such
XML to be generated, but this was never part of the official
nifti-1 specification.
Threaded View
| Title | Author | Date |
|---|---|---|
| Mark Jenkinson | Feb 28, 2011 | |
| Mark Jenkinson | Mar 15, 2011 | |
| Cinly Ooi | Mar 15, 2011 | |
| Cinly Ooi | Mar 2, 2011 | |
| Ged Ridgway | Mar 7, 2011 | |
| Jon Clayden | Mar 5, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Andrew Janke | Mar 1, 2011 | |
| Cinly Ooi | Mar 2, 2011 | |
| Satrajit Ghosh | Mar 5, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Denis Rivière | Feb 28, 2011 | |
| Cinly Ooi | Mar 1, 2011 | |
| Brandon Whitcher | Mar 1, 2011 | |
| Satrajit Ghosh | Feb 28, 2011 | |
| Jonas Larsson | Mar 1, 2011 | |
| Mark Horsfield | Mar 1, 2011 | |
| Andrew Janke | Mar 1, 2011 | |
| Jochen Weber | Feb 28, 2011 | |
| Randall Frank | Mar 1, 2011 | |
| Michael Martinez | Feb 28, 2011 | |
| Cinly Ooi | Feb 28, 2011 | |
| Chris Rorden | Feb 28, 2011 | |
