function Write4dfp(imageData, filename, varargin)

% imageData = Write4dfp(imData, filename, varargin)

%

% Description:

% Writes a 4dfp image given the image data and a path for the filename.4dfp.{img,ifh} file pair.

%

% Usage:

% >> Write4dfp(imageData, 'C:\path\to\subject_mpr.4dfp.img');

%

% Required Parameters:

% imageData - a 3D or 4D image matrix in the format [x, y, z] or [x, y, z, time]

% filename - A path to where the file.4dfp.{img,ifh} will be saved.

%

% Optional Positional Parameter:

% endianess - specifiy either ieee-le, littleendian, ieee-be, or bigendian

%

% Author:

% Jarod L Roland

% Department of Neurosurgery

% Washington University School of Medicine in St. Louis

%

% parse argumengts

params = inputParser;

addRequired(params, 'imageData', @(x) (ndims(imageData) == 3 || ndims(imageData) == 4));

addRequired(params, 'filename', @ischar);

addOptional(params, 'endianess', 'ieee-le', @ischar); % specifiy ieee-le, littleendian, ieee-be, or bigendian

parse(params, imageData, filename, varargin{:});

% make sure imageData is 3D or 4D

assert(ndims(imageData) == 3 || ndims(imageData) == 4, 'Error')

% parse the filename

[tokens] = regexpi(filename, '(.*\.4dfp)(\.img|\.ifh)$?', 'tokens');

assert(~isempty(tokens), 'Error: Filename must of the form path\to\file.4dfp(.ifh|.img) where either .ifh or .img is required.')

imageFilename = [tokens{1}{1} '.img'];

headerFilename = [tokens{1}{1} '.ifh'];

% parse endianess

endianess = params.Results.endianess;

if(strcmp(endianess, 'littleendian') || strcmp(endianess, 'ieee-le'))

endianess = 'ieee-le';

endianessLong = 'littleendian';

elseif(strcmp(endianess, 'bigendian') || strcmp(endianess, 'ieee-be'))

endianess = 'ieee-be';

endianessLong = 'bigendian';

else

error(['Error: invalid endianess parameter provided: ' endianess])

end

% make sure files don't already exist

assert(~exist(imageFilename, 'file'), ['Error: File "' imageFilename '" already exists']);

assert(~exist(headerFilename, 'file'), ['Error: File "' headerFilename '" already exists']);

% write img file

imageFile = fopen(imageFilename, 'w');

assert(imageFile > 0, ['Error: Failed to open ' imageFilename])

fwrite(imageFile, single(imageData), 'float', 0, endianess);

fclose(imageFile);

% write ifh file

imgDims = size(imageData);

if(ndims(imageData) == 3)

imgDims(4) = 1;

end

[~, imageFilenameShort, ~] = fileparts(imageFilename);

headerFile = fopen(headerFilename, 'w');

assert(headerFile > 0, ['Error: Failed to open ' headerFilename])

fprintf(headerFile, 'INTERFILE :=\r\n');

fprintf(headerFile, 'version of keys := 3.3\r\n');

fprintf(headerFile, 'number format := float\r\n');

fprintf(headerFile, 'conversion program := Matlab\r\n');

fprintf(headerFile, ['name of data file := ' imageFilenameShort '.img\r\n']);

fprintf(headerFile, 'number of bytes per pixel := 4\r\n');

fprintf(headerFile, ['imagedata byte order := ' endianessLong '\r\n']);

fprintf(headerFile, 'orientation := 2\r\n');

fprintf(headerFile, 'number of dimensions := 4\r\n');

fprintf(headerFile, 'matrix size [1] := %d\r\n', imgDims(1));

fprintf(headerFile, 'matrix size [2] := %d\r\n', imgDims(2));

fprintf(headerFile, 'matrix size [3] := %d\r\n', imgDims(3));

fprintf(headerFile, 'matrix size [4] := %d\r\n', imgDims(4));

fprintf(headerFile, 'scaling factor (mm/pixel) [1] := 3.000000\r\n');

fprintf(headerFile, 'scaling factor (mm/pixel) [2] := 3.000000\r\n');

fprintf(headerFile, 'scaling factor (mm/pixel) [3] := 3.000000\r\n');

fprintf(headerFile, 'mmppix := 3.000000 -3.000000 -3.000000\r\n');

fprintf(headerFile, 'center := 73.5000 -87.0000 -84.0000\r\n');

fclose(headerFile);