%  Load NIfTI / Analyze header without applying any appropriate affine
%  geometric transform or voxel intensity scaling. It is equivalent to
%  hdr field when using load_untouch_nii to load dataset. Support both
%  *.nii and *.hdr file extension. If file extension is not provided,
%  *.hdr will be used as default.
%
%  Usage: [header, ext, filetype, machine] = load_untouch_header_only(filename)
%
%  filename - NIfTI / Analyze file name.
%
%  Returned values:
%
%  header - struct with NIfTI / Analyze header fields.
%
%  ext - NIfTI extension if it is not empty.
%
%  filetype	- 0 for Analyze format (*.hdr/*.img);
%		  1 for NIFTI format in 2 files (*.hdr/*.img);
%		  2 for NIFTI format in 1 file (*.nii).
%
%  machine    - a string, see below for details. The default here is 'ieee-le'.
%
%    'native'      or 'n' - local machine format - the default
%    'ieee-le'     or 'l' - IEEE floating point with little-endian
%                           byte ordering
%    'ieee-be'     or 'b' - IEEE floating point with big-endian
%                           byte ordering
%    'vaxd'        or 'd' - VAX D floating point and VAX ordering
%    'vaxg'        or 'g' - VAX G floating point and VAX ordering
%    'cray'        or 'c' - Cray floating point with big-endian
%                           byte ordering
%    'ieee-le.l64' or 'a' - IEEE floating point with little-endian
%                           byte ordering and 64 bit long data type
%    'ieee-be.l64' or 's' - IEEE floating point with big-endian byte
%                           ordering and 64 bit long data type.
%
%  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 [hdr, ext, filetype, machine] = load_untouch_header_only(filename)

   if ~exist('filename','var')
      error('Usage:  [header, ext, filetype, machine] = load_untouch_header_only(filename)');
   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
   %
   [hdr, filetype, fileprefix, machine] = load_nii_hdr(filename);

   if filetype == 0
      hdr = load_untouch0_nii_hdr(fileprefix, machine);
      ext = [];
   else
      hdr = load_untouch_nii_hdr(fileprefix, machine, filetype);

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

   %  Set bitpix according to datatype
   %
   %  /*Acceptable values for datatype are*/
   %
   %     0 None                     (Unknown bit per voxel) % DT_NONE, DT_UNKNOWN
   %     1 Binary                         (ubit1, bitpix=1) % DT_BINARY
   %     2 Unsigned char         (uchar or uint8, bitpix=8) % DT_UINT8, NIFTI_TYPE_UINT8
   %     4 Signed short                  (int16, bitpix=16) % DT_INT16, NIFTI_TYPE_INT16
   %     8 Signed integer                (int32, bitpix=32) % DT_INT32, NIFTI_TYPE_INT32
   %    16 Floating point    (single or float32, bitpix=32) % DT_FLOAT32, NIFTI_TYPE_FLOAT32
   %    32 Complex, 2 float32      (Use float32, bitpix=64) % DT_COMPLEX64, NIFTI_TYPE_COMPLEX64
   %    64 Double precision  (double or float64, bitpix=64) % DT_FLOAT64, NIFTI_TYPE_FLOAT64
   %   128 uint8 RGB                 (Use uint8, bitpix=24) % DT_RGB24, NIFTI_TYPE_RGB24
   %   256 Signed char            (schar or int8, bitpix=8) % DT_INT8, NIFTI_TYPE_INT8
   %   511 Single RGB              (Use float32, bitpix=96) % DT_RGB96, NIFTI_TYPE_RGB96
   %   512 Unsigned short               (uint16, bitpix=16) % DT_UNINT16, NIFTI_TYPE_UNINT16
   %   768 Unsigned integer             (uint32, bitpix=32) % DT_UNINT32, NIFTI_TYPE_UNINT32
   %  1024 Signed long long              (int64, bitpix=64) % DT_INT64, NIFTI_TYPE_INT64
   %  1280 Unsigned long long           (uint64, bitpix=64) % DT_UINT64, NIFTI_TYPE_UINT64
   %  1536 Long double, float128  (Unsupported, bitpix=128) % DT_FLOAT128, NIFTI_TYPE_FLOAT128
   %  1792 Complex128, 2 float64  (Use float64, bitpix=128) % DT_COMPLEX128, NIFTI_TYPE_COMPLEX128
   %  2048 Complex256, 2 float128 (Unsupported, bitpix=256) % DT_COMPLEX128, NIFTI_TYPE_COMPLEX128
   %
   switch hdr.dime.datatype
   case   1,
      hdr.dime.bitpix = 1;  precision = 'ubit1';
   case   2,
      hdr.dime.bitpix = 8;  precision = 'uint8';
   case   4,
      hdr.dime.bitpix = 16; precision = 'int16';
   case   8,
      hdr.dime.bitpix = 32; precision = 'int32';
   case  16,
      hdr.dime.bitpix = 32; precision = 'float32';
   case  32,
      hdr.dime.bitpix = 64; precision = 'float32';
   case  64,
      hdr.dime.bitpix = 64; precision = 'float64';
   case 128,
      hdr.dime.bitpix = 24; precision = 'uint8';
   case 256
      hdr.dime.bitpix = 8;  precision = 'int8';
   case 511
      hdr.dime.bitpix = 96; precision = 'float32';
   case 512
      hdr.dime.bitpix = 16; precision = 'uint16';
   case 768
      hdr.dime.bitpix = 32; precision = 'uint32';
   case 1024
      hdr.dime.bitpix = 64; precision = 'int64';
   case 1280
      hdr.dime.bitpix = 64; precision = 'uint64';
   case 1792,
      hdr.dime.bitpix = 128; precision = 'float64';
   otherwise
      error('This datatype is not supported');
   end

   tmp = hdr.dime.dim(2:end);
   tmp(find(tmp < 1)) = 1;
   hdr.dime.dim(2:end) = tmp;


   %  Clean up after gunzip
   %
   if exist('gzFileName', 'var')
      rmdir(tmpDir,'s');
   end


   return					% load_untouch_header_only

