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load_nii.m
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load_nii.m
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% 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 ([email protected])
%
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
% 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);
return % load_nii