function vol2exp(d, sample, output_file_base, frame)

%VOL2EXP writes input for the IRIS Explorer latin module.
%
% VOL2EXP( INPUT [, SAMPLE [, OUTPUT_FILE_BASE [, FRAME]]] )
%
% INPUT is the input .mnc or .img file or structure from 
% fmris_read_image.
%
% SAMPLE is a 3 x 3 matrix whose rows are the start, step and stop
% indices, and whose columns are the x y and z directions. Default is 
% [1 1 d.dim(1); 1 1 d.dim(2); 1 1 d.dim(3)] i.e. all the data.
%
% OUPUT_FILE_BASE: writes INPUT to OUPUT_FILE_BASE.exp. 
% Default is INPUT minus extension if INPUT is file name.
%
% FRAME: frame, default=1.

if nargin < 3
   output_file_base=[];
end
if nargin < 4
   frame=1;
end

if ischar(d)
   input_file=d;
   d=fmris_read_image(input_file,0,0);
   numslices=d.dim(3);
   d=fmris_read_image(input_file,1:numslices,frame);
else
   input_file=[d.file_path d.file_name];
end

if isempty(output_file_base)
   output_file_base=input_file(1:(min(findstr('.',input_file))-1));
end
ext=input_file(min(findstr('.',input_file))+(1:3));
isminc= all(lower(ext)=='mnc');

if nargin < 2
   sample=[];
end
if isempty(sample)
   sample=[1 1 d.dim(1); 1 1 d.dim(2); 1 1 d.dim(3)]
end

% For .mnc files, emma flips the slices if the voxel sizes are <0, 
% so we have to flip the voxel sizes and origin:

for i=1:2
   if d.vox(i)<0 & isminc
      d.origin(i)=d.origin(i)+d.vox(i).*(d.dim(i)-1);
      d.vox(i)=-d.vox(i);
   end
end

x=sample(1,1):sample(1,2):sample(1,3);
y=sample(2,1):sample(2,2):sample(2,3);
z=sample(3,1):sample(3,2):sample(3,3);

sizes=[length(x) length(y) length(z)]
m=[min(x) min(y) min(z); max(x) max(y) max(z)];
bbox=(m-1).*[d.vox; d.vox]+[d.origin; d.origin]

fid=fopen([output_file_base '.exp'],'w');
% first 3 are dimension sizes as 4-byte integers:
fwrite(fid,sizes,'int');
% next 6 are bounding box as 4-byte floats: 
fwrite(fid,bbox,'float');
% rest are the data as 4-byte floats:
fwrite(fid,d.data(x,y,z),'float');
fclose(fid)

return