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Tools for NIfTI and ANALYZE image

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Tools for NIfTI and ANALYZE image

by

Jimmy Shen (view profile)

 

23 Oct 2005 (Updated )

Load, save, make, reslice, view (and edit) both NIfTI and ANALYZE data on any platform

load_nii(filename, img_idx, dim5_idx, dim6_idx, dim7_idx, ...
%  Load NIFTI or ANALYZE dataset. Support both *.nii and *.hdr/*.img
%  file extension. If file extension is not provided, *.hdr/*.img will
%  be used as default.
%
%  A subset of NIFTI transform is included. For non-orthogonal rotation,
%  shearing etc., please use 'reslice_nii.m' to reslice the NIFTI file.
%  It will not cause negative effect, as long as you remember not to do
%  slice time correction after reslicing the NIFTI file. Output variable
%  nii will be in RAS orientation, i.e. X axis from Left to Right,
%  Y axis from Posterior to Anterior, and Z axis from Inferior to
%  Superior.
%  
%  Usage: nii = load_nii(filename, [img_idx], [dim5_idx], [dim6_idx], ...
%			[dim7_idx], [old_RGB], [tolerance], [preferredForm])
%  
%  filename  - 	NIFTI or ANALYZE file name.
%  
%  img_idx (optional)  -  a numerical array of 4th dimension indices,
%	which is the indices of image scan volume. The number of images
%	scan volumes can be obtained from get_nii_frame.m, or simply
%	hdr.dime.dim(5). Only the specified volumes will be loaded. 
%	All available image volumes will be loaded, if it is default or
%	empty.
%
%  dim5_idx (optional)  -  a numerical array of 5th dimension indices.
%	Only the specified range will be loaded. All available range
%	will be loaded, if it is default or empty.
%
%  dim6_idx (optional)  -  a numerical array of 6th dimension indices.
%	Only the specified range will be loaded. All available range
%	will be loaded, if it is default or empty.
%
%  dim7_idx (optional)  -  a numerical array of 7th dimension indices.
%	Only the specified range will be loaded. All available range
%	will be loaded, if it is default or empty.
%
%  old_RGB (optional)  -  a scale number to tell difference of new RGB24
%	from old RGB24. New RGB24 uses RGB triple sequentially for each
%	voxel, like [R1 G1 B1 R2 G2 B2 ...]. Analyze 6.0 from AnalyzeDirect
%	uses old RGB24, in a way like [R1 R2 ... G1 G2 ... B1 B2 ...] for
%	each slices. If the image that you view is garbled, try to set 
%	old_RGB variable to 1 and try again, because it could be in
%	old RGB24. It will be set to 0, if it is default or empty.
%
%  tolerance (optional) - distortion allowed in the loaded image for any
%	non-orthogonal rotation or shearing of NIfTI affine matrix. If 
%	you set 'tolerance' to 0, it means that you do not allow any 
%	distortion. If you set 'tolerance' to 1, it means that you do 
%	not care any distortion. The image will fail to be loaded if it
%	can not be tolerated. The tolerance will be set to 0.1 (10%), if
%	it is default or empty.
%
%  preferredForm (optional)  -  selects which transformation from voxels
%	to RAS coordinates; values are s,q,S,Q.  Lower case s,q indicate
%	"prefer sform or qform, but use others if preferred not present". 
%	Upper case indicate the program is forced to use the specificied
%	tranform or fail loading.  'preferredForm' will be 's', if it is
%	default or empty.	- Jeff Gunter
%
%  Returned values:
%  
%  nii structure:
%
%	hdr -		struct with NIFTI header fields.
%
%	filetype -	Analyze format .hdr/.img (0); 
%			NIFTI .hdr/.img (1);
%			NIFTI .nii (2)
%
%	fileprefix - 	NIFTI filename without extension.
%
%	machine - 	machine string variable.
%
%	img - 		3D (or 4D) matrix of NIFTI data.
%
%	original -	the original header before any affine transform.
%  
%  Part of this file is copied and modified from:
%  http://www.mathworks.com/matlabcentral/fileexchange/1878-mri-analyze-tools
%  
%  NIFTI data format can be found on: http://nifti.nimh.nih.gov
%  
%  - Jimmy Shen (jimmy@rotman-baycrest.on.ca)
%
function nii = load_nii(filename, img_idx, dim5_idx, dim6_idx, dim7_idx, ...
			old_RGB, tolerance, preferredForm)

   if ~exist('filename','var')
      error('Usage: nii = load_nii(filename, [img_idx], [dim5_idx], [dim6_idx], [dim7_idx], [old_RGB], [tolerance], [preferredForm])');
   end

   if ~exist('img_idx','var') | isempty(img_idx)
      img_idx = [];
   end

   if ~exist('dim5_idx','var') | isempty(dim5_idx)
      dim5_idx = [];
   end

   if ~exist('dim6_idx','var') | isempty(dim6_idx)
      dim6_idx = [];
   end

   if ~exist('dim7_idx','var') | isempty(dim7_idx)
      dim7_idx = [];
   end

   if ~exist('old_RGB','var') | isempty(old_RGB)
      old_RGB = 0;
   end

   if ~exist('tolerance','var') | isempty(tolerance)
      tolerance = 0.1;			% 10 percent
   end

   if ~exist('preferredForm','var') | isempty(preferredForm)
      preferredForm= 's';		% Jeff
   end

   v = version;

   %  Check file extension. If .gz, unpack it into temp folder
   %
   if length(filename) > 2 & strcmp(filename(end-2:end), '.gz')

      if ~strcmp(filename(end-6:end), '.img.gz') & ...
	 ~strcmp(filename(end-6:end), '.hdr.gz') & ...
	 ~strcmp(filename(end-6:end), '.nii.gz')

         error('Please check filename.');
      end

      if str2num(v(1:3)) < 7.1 | ~usejava('jvm')
         error('Please use MATLAB 7.1 (with java) and above, or run gunzip outside MATLAB.');
      elseif strcmp(filename(end-6:end), '.img.gz')
         filename1 = filename;
         filename2 = filename;
         filename2(end-6:end) = '';
         filename2 = [filename2, '.hdr.gz'];

         tmpDir = tempname;
         mkdir(tmpDir);
         gzFileName = filename;

         filename1 = gunzip(filename1, tmpDir);
         filename2 = gunzip(filename2, tmpDir);
         filename = char(filename1);	% convert from cell to string
      elseif strcmp(filename(end-6:end), '.hdr.gz')
         filename1 = filename;
         filename2 = filename;
         filename2(end-6:end) = '';
         filename2 = [filename2, '.img.gz'];

         tmpDir = tempname;
         mkdir(tmpDir);
         gzFileName = filename;

         filename1 = gunzip(filename1, tmpDir);
         filename2 = gunzip(filename2, tmpDir);
         filename = char(filename1);	% convert from cell to string
      elseif strcmp(filename(end-6:end), '.nii.gz')
         tmpDir = tempname;
         mkdir(tmpDir);
         gzFileName = filename;
         filename = gunzip(filename, tmpDir);
         filename = char(filename);	% convert from cell to string
      end
   end

   %  Read the dataset header
   %
   [nii.hdr,nii.filetype,nii.fileprefix,nii.machine] = load_nii_hdr(filename);

   %  Read the header extension
   %
%   nii.ext = load_nii_ext(filename);

   %  Read the dataset body
   %
   [nii.img,nii.hdr] = load_nii_img(nii.hdr,nii.filetype,nii.fileprefix, ...
		nii.machine,img_idx,dim5_idx,dim6_idx,dim7_idx,old_RGB);

   %  Perform some of sform/qform transform
   %
   nii = xform_nii(nii, tolerance, preferredForm);

   %  Clean up after gunzip
   %
   if exist('gzFileName', 'var')

      %  fix fileprefix so it doesn't point to temp location
      %
      nii.fileprefix = gzFileName(1:end-7);
      rmdir(tmpDir,'s');
   end

   return					% load_nii

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