hdr2Nhdr.m

function [fid] = hdr2Nhdr(hdr,mat,fn) 

	% hdr an existing nrrd hdr with the same dimentions
	% fn - the name of the file to be written (with no extension).
	% mat - the data file
	if ~isfield(hdr,'spaceorigin')
	    hdr.spaceorigin = [-41.5,-41.5,-39];
	end

	fid = fopen([fn '.nhdr'], 'w');
	[path,fn_short] = fileparts(fn);

	fprintf(fid, ['NRRD0004\n' ...
		        '# Complete NRRD file format specification at:\n' ...
		        '# http://teem.sourceforge.net/nrrd/format.html\n' ...
		        'type: double\n' ...
		        'dimension: 3\n' ...
		        'space: %s\n' ...
		        'sizes: %d %d %d\n' ...
		        'space directions: (%g,%g,%g) (%g,%g,%g) (%g,%g,%g)\n' ...
		        'centerings: cell cell cell\n'...                
		        'kinds: %s %s %s\n' ...
		        'endian: little\n' ...
		        'encoding: gzip\n' ...
		        'space units: "mm" "mm" "mm"\n'...
		        'space origin: (%g,%g,%g)\n' ...
		        'data file: %s.raw.gz\n'], ...
		  hdr.space, hdr.sizes(1:3), hdr.spacedirections, ...
		  char(hdr.kinds(1)),char(hdr.kinds(2)),char(hdr.kinds(3)), hdr.spaceorigin, fn_short);


	  fclose(fid);
	  
	  
	  fid = fopen([fn '.raw'], 'w');
	  fwrite(fid, mat, 'double');
	  fclose(fid);
	  system(['rm -f ' fn '.raw.gz && gzip ' fn '.raw']); % compress

end